Underhouse digout - tips, advise, gotcha's and money saving points (wanted)

ok, perhaps I need to pose things as actual questions and not hit people with a wall of text?

1. Has anyone used Dexpan before?

How did you find it? Did you use it to break up ironstone (Sydney Sandstone with the fleck of iron oxide running through it)?

2. Can anyone give me an approximate size required to span say a 10m - 15m metal beam span (to hold up under the house in replacement of piers)? What is the typical cost? I'm most interested in knowing the beam height. NOTE: I am not looking nor holding anyone to random over their advise on this, I'm just wanting to know what the typical size and costings are so that when I go to purchase on advise from an engineer, I'm going to be edumacated up slightly so as not to get hoodwinked, that's all

)

Try this

http://www.onesteel.com/images/db_im...g_3rdednp1.pdf

6-9m is span more practical , big difference between 10 and 15m.

Cheers Pulse


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Sounds like a serious amount of sandstone you will be removing, 15mx20mx2m= 60m3, approx 120 ton?

Do you have a price for the dexspan, usually these types of speciality chemicals are expensive. Maybe there is a more efficient way like you could cut it up into blocks using one of those concrete chainsaws?

I get 600m3 or 1200 ton. What is the plan for disposal? Do you think cutting grooves with an electric demo saw would be quicker? Can't get a dingo in with an attachment? Two years might be optimistic, that is a massive job.


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Rotary drill, plus pin and feathers once you have a splitting face might give faster progress. I'd be using a demo saw myself cutting blocks then splitting off with the pins and feathers, about $25 a set and you'd probably want a minimum of eight sets along with a four flute SDS drill, can't remember the sixe either 16mm or 18mm I think but it is given when you buy the pins.

The idea is to cut in as far as you can, drill into the splits then use the wedges (pins and feathers) to force the split.

Originally Posted by Pulse

I get 600m3 or 1200 ton.

Oops my bad, that is a serious amount of rock to get rid of, maybe it would be useful to someone if removed in blocks as john suggested.

I've gotta wonder how much it would cost to have that amount of rock dug and removed and what the house might be like after all the vibrations.
Not to mention how many jackhammers you might go through!

A 200 litre drum of spakfilla might come in handy, plus a bit of mortar repair material. Depends on the rock, sandstone isn't that bad but in those quantities I can't see anyone moving that much material before you lost the will to live.

Removed? No problem, Just fill your pockets with the sand and rock and as you walk around the block each night just sprinkle it around the neighbourhood....
id be more concerned with what your wrists and back would be like after spending 2 years on the demolition hammer... And how many teeth you will have left. The rock saw idea sounds less damaging to your body and the foundations

Surely this is a joke ? Just lift the house.

Pretty funny though, just thinking about it


xxxxxxxxxxxxxx

Sorry all, I was away on a short break...

Originally Posted by Pulse

Try this

http://www.onesteel.com/images/db_im...g_3rdednp1.pdf

6-9m is span more practical , big difference between 10 and 15m.

Cheers Pulse

Thanks

This is exactly what I needed to know

Obviously, I'd prefer a longer span but the area will be subdivided anyhow so if two smaller beams are cheaper and easier to work with then so be it

Originally Posted by paddyjoy

Sounds like a serious amount of sandstone you will be removing, 15mx20mx2m= 60m3, approx 120 ton?

Do you have a price for the dexspan, usually these types of speciality chemicals are expensive. Maybe there is a more efficient way like you could cut it up into blocks using one of those concrete chainsaws?

There's been a change in the size (or a more accurate measurements made!)

It's looking more like it will be 10m wide x 2.5m (down) x 8 - 9m wide = 225m3

Then depending if I survive my mad exploit or not, I would like to dig out another section which would be for a bushfire safe room, that would be about 3m (wide) x 6m (long) x 3m (down) = 54m3

I priced the Dexpan at $220 per box. The rep in Australia reckons a box will do 10 linear meters, but I'm thinking you need 3 rows of holes drilled for breaking so that may mean 3m per box. He thought I might be able to get more as he thinks I may be able to break at 400 mm - 450 mm spacing but all this has to be tested first

For those wondering what Dexpan is, here is the ad for it (I am not affiliated with them in any way)

https://www.youtube.com/watch?v=KgOtMQcMnH0
https://www.youtube.com/watch?v=6soi6LnnO2w

and some video's from some people who used it

https://www.youtube.com/watch?v=dPfqitM2Dt4
https://www.youtube.com/watch?v=oT6AojG-2Ho

Originally Posted by Pulse

I get 600m3 or 1200 ton. What is the plan for disposal? Do you think cutting grooves with an electric demo saw would be quicker? Can't get a dingo in with an attachment? Two years might be optimistic, that is a massive job.

I have a sloping block and plenty of area to build up if I wanted to dump the rock fragments at the back

I also back onto crown land. Now before people cry foul and come after me with knives, the land is sloped after my property, with rock faces around 6 - 7m and it's land that we have repeatably asked the federal government to assist in in keeping it clear from lantana and fallen tree's but they are not interested and just tell us 'look after it yourself and keep it maintained if you wish'. It's an eyesore actually but because it's down the back and no-one goes there, well, not in the last 30 years, I could actually fill in the land areas and improve the looks a lot. I wouldn't even consider this if I thought it wouldn't improve the area, after all, I have to live with what get's placed there

Yes, the job is massive but I work in IT and there's hints my role will be gone before too long, maybe by the end of this year and my prospects of getting another are lowish so I think I may may lots of time on my hands (I have plenty of skills, love to keep learning, set up my own IT systems to learn at home etc but I can't fight the bias out there about older workers and their supposedly inability to understanding computing - even though I direct younger people at work who supposedly know it all - go figure!)

Originally Posted by johnc

Rotary drill, plus pin and feathers once you have a splitting face might give faster progress. I'd be using a demo saw myself cutting blocks then splitting off with the pins and feathers, about $25 a set and you'd probably want a minimum of eight sets along with a four flute SDS drill, can't remember the sixe either 16mm or 18mm I think but it is given when you buy the pins.

The idea is to cut in as far as you can, drill into the splits then use the wedges (pins and feathers) to force the split.

I have managed to find a technique that is working quite well at present

After digging down, I go back and slice chunks off the walls all the way down to the bottom of the rock wall. This is yielding quite a good result, although I have to stop every so often to shovel out a few wheelbarrows (the wheel barrow at the moment cannot fit under the house, so it's a tough haul shoveling it upwards, through the side manhole and into the barrow for removal down the back of my property)

It's surprising addictive once you start getting slices happening, you always want to chop just one more off before you take a break - lets see how long this last for!

The idea of drilling is a good one. If I go the Dexpan route as well, I need to buy a decent rotary hammer anyhow. I've been looking at the Hitachi SDS rotary drills, around 45mm, but they are not cheap, not too far off what I paid for my Hitachi demolition hammer actually. The Hitachi's have a 3 year warranty, I figure if they break in that time I'll put in a warranty claim and perhaps get a replacement

I'll look at those pins/feathers. Using them vertically may be a challenge though, I have about 500mm between the rock and the underneath of my house (it gets lower the further underneath I go). I have already dug out a working space of about 1.5m long, down about 1.2m, so I now have a small space to stand up in. Maybe those pins/feathers could be used to go sideways into the rock?

Originally Posted by phild01

I've gotta wonder how much it would cost to have that amount of rock dug and removed and what the house might be like after all the vibrations.
Not to mention how many jackhammers you might go through!

I'd hate to think how much - I simply do not have the money to pay someone else

If I did, I'd happily pay them, this is hard work

If I can get the job done in 2 years, the demolition hammer has a 3 year warranty - If it fails in that 3 years I'll be asking Hitachi for a replacement )

The house was originally dug down to rock, that's why it's a PITA of a job to dig down

If it was on soil I'd be a happy man

I've gone about 200mm to the peers and to the footings at present and not a single crack or movement anywhere

I'm not going any closer and digging in a straight line until the engineer comes and gives me directions about what I need to do

The house is around 60 years old and has one hairline crack through one brick but that was there more than 20 years ago before I moved in, I don't think the house is going anywhere and I don't think the work I'm doing is going to unsettle it that much (at least that's my hope!)

Originally Posted by johnc

A 200 litre drum of spakfilla might come in handy, plus a bit of mortar repair material. Depends on the rock, sandstone isn't that bad but in those quantities I can't see anyone moving that much material before you lost the will to live.

Every time I don't feel like getting up and getting out the demolition hammer I tell myself "It's not going to do it itself"

The other driver is I have not got the $1000 perceived value from my demolition hammer yet! I cannot stop until I've at least had my monies worth out of it )

Originally Posted by mudbrick

Removed? No problem, Just fill your pockets with the sand and rock and as you walk around the block each night just sprinkle it around the neighbourhood....
id be more concerned with what your wrists and back would be like after spending 2 years on the demolition hammer... And how many teeth you will have left. The rock saw idea sounds less damaging to your body and the foundations

I was considering getting a weightlifters belt actually (recommended by the guys at gasweld where I purchased the demolition hammer from)

I'm also thinking this work is part of compulsory fitness program. I have plenty of fat I could do with loosing and I have noticed my upper body strength improving already, but it's not going to turn me into any hulk or anything like that

But your right, this is in fact my greatest concern, what happens if I break my body somehow in the process and cannot complete the work myself

This is another reason I am looking at Dexpan. A saw will be my last resort because it adds yet another tool purchase expense and because the excavation is below land-line, the water used fon the cutting saw would then have to be pumped out as well, something else I'd need to buy

Originally Posted by ringtail

Surely this is a joke ? Just lift the house.

I assume you replying to me? or to the person suggesting putting the sand in my pockets and walking around the block to dispose of it?

It's no joke what I'm doing. I have already started. I have my demolition hammer and I've already started (ok, so I only have a 1.5 x about 1.5m hold dug out already) but it's underway

I've contacted an engineer who when he's back from holidays will come and give me a report and detail what I need to do etc

I looked at house lifting but the place is brick veneer and the idiots who built the place (I'm looking at you Lend Lease) dug the land down till they hit rock, which might have been ok except it means that 1/3 of the house I cannot put sub-floor ventilation in because punching holes in the bricks will result in the ventilation being above the floor line ;-(
So, I'd have to dig down on one 20m side of the house to get the house jacking equipment in to then lift the house

If I had the money, then yeah, lifting would be the best, it would give me exactly what I want in terms of maximum storage underneath, it would solve the sub-floor ventilation issue but the cost is something I cannot afford, hence why I am digging down and doing the grunt work myself

Unless you know someone who would lift my house for say 20K - 30K? But I fear it would cost a lot more than that, so I have no choice but to continue the hard slog myself

Yep, I was referring to you. You nutter . 20 -30 k will lift a house on stumps easy. The expense is in everything that comes after the lift . May the force be with you

Originally Posted by maveri

If I can get the job done in 2 years, the demolition hammer has a 3 year warranty - If it fails in that 3 years I'll be asking Hitachi for a replacement )

...no neighbours or maybe they are deaf

Have you checked out this site

Originally Posted by hrt22

Have you checked out this site

Originally Posted by ringtail

Yep, I was referring to you. You nutter . 20 -30 k will lift a house on stumps easy. The expense is in everything that comes after the lift . May the force be with you

lol

I searched and searched to try and find prices on house lifting and all I could find was loose approximations that would put it in the 50K+ price bracket, hence I dismissed it

At 20K, I would consider it actually. I would much rather lift than dig, especially for that amount

Plumbing I have a friend who would see me right on pricing and a sparky friend also

Bricking in I'd be at a loss for, although my neighbor is in the building game and could probably see me right

My father-in-law was a cabinet marker and had a building license but gave it up to retire, he'd pitch in where he could too, if I could get him out of him motor home

I clearly should have investigated lifting more closely, I seriously thought it was way more than this. I don't know how many youtube video's I watched (mainly US) watching house lifts and house digouts, even the houses that fell while being lifted!

Originally Posted by Marc

I thought I was a tad opinionated, but it seems I have found one that dwarfs me by miles.

As a side comment, why is it that people think they have to "disclose" their "non" affiliation. Are we politicians? Whoohoo I am not affiliated, what does that mean? A post is a free plug, why not get paid for doing so? Or conversely, why do it for free?

I'm on an IT forum a lot and it's common practice there, if spouting about a product, to disclose if you are affiliated or not with the product or service in question. It was just out of habit that I included that here

Originally Posted by phild01

...no neighbours or maybe they are deaf

I have great neighbors

Most have lifted here since the places were first built (I'm not an original)

I've had a few comments about the Jack Hammering, mainly because they are interested in knowing what I'm doing than making complaints

They are the sort of neighbors who would rather keep council and officialdom out of our lives than have them prying into what goes on someone's private land, if you get what I mean

2 years of hammering might wear a bit think on them though, although I'm down a small embankment so it's not like the sound is going across on the level to their homes

The neighbor on one side has an easement between us, the neighbor on the other side has my external laundry blocking the sound and those at the back are across a valley, probably a good km or more away

Still, I would visit them every so often to check-in to make sure they were not getting pissed off with the constant noise and I'd have a few well intended break periods to give them some relief

I guess it's a matter of being reasonable with them I guess

Originally Posted by maveri

.... and those at the back are across a valley, probably a good km or more away

Hornsby area?

So when are we going to see some pictures

Ourbuild the making of the man cave

It's not too late to investigate lifting it.
id guess underpinning companies and or builders would be the ones to call.

Originally Posted by paddyjoy

So when are we going to see some pictures

I've only really just got started, so there is nothing much to see but the small workings of the beginnings of a hole

I actually got enthused by this whole mad idea when I cleaned out my garden shed and found a coil of agpipe that I purchased like 15 years beforehand and never used.

So I decided to use the agpipe on a water situation that has annoyed me for years. I dragged out the agpipe and dug along and started to put the pipe in, then I hit rock.
I tried drilling it with a normal drill and hammering it out with a hammer and chisel. Then I used my old axe which smashed up the rock bit by bit until after the sun fried my brain for long enough to get some sense into it.
When my brain finally got working, I decide that doing things like they did 100 years ago was stupid and it was about time I bought myself a decent tool as life had to be better than just doing things the hard way all the time - so I went and got myself the Hitachi demolition hammer.

I dug the hole for the agpipe in a day! (I had chipped away at the rock for like 2 weeks on/off before this).

The shear delight of seeing progress so easily when one has the right tool resulting in me opening up the side manhole and starting to dig there with my new toy.
I also ripped out the rocks that had been smashing my lawnmower blades for the past 2 decades around my yard as well - I've been inspired, just hope the inspiration lasts. Each time I hit my head on the bearers under my house I give a smirk and mutter an expletive and say 'one day, one day I'm not going to be friggin hitting my head on you any longer'. This is still proving to be a good motivator just thinking about the joy of being able to walk under my house and not hit my head

I can just stand up in the bottom of the small hole I have dug and not hit my head on the floor boards (but still hit it on the bearers). I think I've got about another 1.5m down still further to go

Lately I've been thinking, I really should be taking photo's properly so as to record the progress

I made a joke with my kids that if this job kills me, just throw me in the hole and fill it in

It really is very very early days and the hole is only just started but I think I took a couple of photo's, I'll see what I can find, but don't expect too much, I'm just a crazy guy with a mad idea at this stage

I've also hit a snag. With the huge storms in Sydney, the hole has been getting filled with water ( I had my wheelbarrow in there and it was almost completely submerged. I have been using the garden hose as a siphon to pump the water out. I need to find a permanent solution. The idiots who put the guttering in have one of the downpipes (and there is nowhere near enough for this house) just going to nowhere. That nowhere fills up with water and is back flowing under the house, which is finding it's way to my little hole and filling it up

ok, I've got some photo's. I can't believe I started this nonsense in January but the photo dates don't lie. I have only had a few days where I have been able to hammer for long period of time and throw in a recent trip away and it all spells slow progress really when one looks at how little I have actually dug out . Still, I know the last time I made what I thought was good progress

Hmmm. I can't seem to upload files

I keep getting an error. I've reduced the file sizes but I suspect it doesn't like the file naming?

When I figure it out I'll put them up (there's not much to see yet though)

Originally Posted by phild01

Hornsby area?

Down south, Hobbit territory

ok, I think I sorted out the file uploading problem

I tried 3 different browsers, looked at other people getting the #2038 error

Even though it states 3mb is ok for jpeg, it's not, I suspect it's encoded on upload which blows out the file size

So, I reduced the sizes even further and voila, it uploaded. Sorry for the lousy resolution as a result...

I would like to know how well the Dexpan goes as well. I have the ironstone type of sandstone and I am a little over with the jackhammering. Mind you I only have about 2 cubic metres to go.

Wow the photos really clarify what you are doing.
drainage is likely to be on of the biggest problems with digging so far below ground level. Water will constantly be flowing into the excavated area giving you issues with whatever you store under there.
I love your enthusiasm but think you should really do so more investigation now before go too far and then end up getting pros involved later and lifting the house or finding you have a permanent swimming pool under the house or whatever. I'm Mostly saying this because the pictures of the Hole with all your stuff still sitting there right beside it makes it look just like something I would do�� and that makes me think about all the times I've started things the hard way only to hear of an easier faster cheaper and better way later on. Just like your chiseling the trench for the ag line.
hopefully the Engineer has some good ideas. What is your plan for access to the Hole, will there be a staircase down to it from outside?

Holy Cr*p

Can I get a dose of your enthusiasm! There has to be an easier way. ?....

If you need more storage, have you considered a shed, or some other external structure!

I did an under house dig several years ago and with the benefit of hindsight, now know what I should have done differently:

.get plans approved so that the later unforeseen sale of the house didn't involve reducing the price to compensate for work unapproved by council.

.get definite blessing of spouse/partner since she had to do more housework/child caring and less socialising with me and others while I self importantly tended to my obsession.

.understand that friends and neighbours who are initially bemused and appear supportive, may well change their mind, especially if they seek and then fail to get official approval for their comparable silly ideas!

Overall I was happy enough but everyone else grew increasingly irritated!

Originally Posted by mudbrick

Wow the photos really clarify what you are doing.
drainage is likely to be on of the biggest problems with digging so far below ground level. Water will constantly be flowing into the excavated area giving you issues with whatever you store under there.
I love your enthusiasm but think you should really do so more investigation now before go too far and then end up getting pros involved later and lifting the house or finding you have a permanent swimming pool under the house or whatever. I'm Mostly saying this because the pictures of the Hole with all your stuff still sitting there right beside it makes it look just like something I would do�� and that makes me think about all the times I've started things the hard way only to hear of an easier faster cheaper and better way later on. Just like your chiseling the trench for the ag line.
hopefully the Engineer has some good ideas. What is your plan for access to the Hole, will there be a staircase down to it from outside?

I've been storing stuff under the house for years, I've started moving it back under further because I've caught up to it with the digging

As I have no time constraints really on getting this done, I figured 2 years for the digging

I've given it some thought about drainage. Where the manhole is, I'll dig a trench outwards, down the same depth as what I dig down to and run a pipe out to the bush (the bush is lower than my land and continues down the valley). I have down pipe that is about 5m to the left of the manhole that just empties onto the ground and has been the cause of water flowing back under the house - I will connect this up to the water removal pipe and solve that issue at the same time

There is no way I'd ever do any of this if it meant having to pay someone else. I'm doing it because I think I can do the majority of the grunt work and therefore that work would be at minimal cost (tools & chisels and perhaps a few drill bits. I've deformed the head on one bull-point chisel already and put a nice curve on the wide chisel - probably from bad technique when I first started). A chisel cost around $40 - $80. One guy at gasweld said he knew of someone who reforms the tips and hardens them again for $20, I think I'll be paying him a few visits

Water has been a problem for a long time and this dig out will force me to fix it once and for all. I'm going to have to stop the water getting under my house and that's going to mean trenching around the outer edge

I have damp issues (have had for years), because of the low clearance (where the manhole is is actually the most clearance, it gets a lot worse at the far opposite end of the house).
I rolled out plastic many years ago and that stopped the damp rising up, so digging down will actually increase the cavity space and if I put proper drainage in under whatever floor I put in, I think I will have improved the damp problems a lot. Before I fill in, I'm going to get advise on what water barrier treatment to put in to stop any water running in sideways

Even if after digging it all out I decide it's not worth creating an actual living space out of it, I'll still be a happy camper because I will be able to actually walk under there to store things (what you see in the photo's is when we dumped things there recently in a hurry. It's normally more ordered than that)

As to underpinning. I was going to ask the Engineer what he recommends. I like the idea of underpinning properly (I watched heaps of video's on that too) but that work would be outside of my confidence range to even consider doing that myself.

I may end up blocking next to the existing footings using concrete blocks with galvanized rods in them drilled down into the rock, filled with concrete mixed with a water repellant of some type.
I know I'd loose some space but it would probably be a job that I could tackle myself with guidance where-as full underpinning I would not be game enough to do myself and this job is about doing as much of the work myself.
My father-in-law actually built his home many years ago himself, from scratch, totally himself while he lived in it (apparently councils will not allow this anymore). He also knows a few builders who would be able to guide me - this job is all about doing as much of the donkey work myself and where necessary, getting expertise in to show me what to do and at a last resort, paying someone to do the actual work

I was talking with someone who has done a fair amount of building work in the area and he reckons, as per a lot of the jobs he's been at, I should be able to go down almost hard against my footings / peers due to the nature of the rock - but I'll take the Engineers advise on this, that is why I have kept away from them by at least 200mm and sloped the sides outwards just in case
I also have a couple of friends who are civil engineers that I could call upon in a pinch. I'm happy to pay people for the right advise though rather than suck freebies off people all the time

I'm going to look into the lifting option again and see if it's outside my price range or not - I was really surprised to hear such a reasonable figure. Lifting would actually give me the most amount of extra space and would solve all my damp issues in one hit. I could then make part of the house a garage also (I don't have one, and most homes in this area don't either. People couldn't afford them years ago and most people learnt to live without one over the years)

Anyhow - once I get the Engineer in and get some advise, I'll know what's feasible and what I'm really in for going forward. Either way, I started digging because I knew no matter what, the digging would have to be done, even if it's just to stop me bumping my head under the house. I just got carried away digging downwards where-as I should have dug sideways more

Access to downstairs may be via internal stairs from another room. Many years ago, a garage was considered down the side but that never happened (like a lot of my ideas). Right above the current hole is the kitchen. It's huge but it's the original and needs to be gutted. We are looking at redoing it but adding a couple of rooms out towards the back in which case the back wall will get opened up and a staircase would go in there. We really prefer split level, getting too old for full stairs. The house is actually tiny compared to most homes (

I already have a shed down the back. To put in more shed storage would require the old one being pulled down and a new bigger one put in it's place. We really love the bush view and don't want to build anything that would block that view so where the shed is now is where a replacement would have to go

I was looking at costings for universal beams. Not that I have any idea of what size I would need but is it like top secret or something when it comes to getting a price? I could only find one place in Queensland that had actual prices on their website for the beams. Blackwoods in Sydney have a set price of 2.5K but that is just an advertised price because they give the same price for all lengths and beam sizes and lengths lol. Everyone else wanted email address and they would send you back a quote - wtf. I just want an approximate price

I just thought, off the top of my head, that if I got a 250 UB 37, galvanized, around 9 - 10m, @ $94.50/m (undelivered, price from Scottmetals), that's around $1000. Quadruple that because I need to replace 2 rows of peers, or even 3 rows perhaps, that's around $4000 - $6000 for beams. Seems a bit cheap. I thought the beams would be around $3000 each but I have no idea at all, so this isn't even a ballpark figure. Then there's the vertical beams to put in also. They would equate to maybe 18m (3m each x 6 columns) (if I do 3 rows of peers), so perhaps another $6000. So I'm totally guessing at around $12K for steel????

Out of interest, how does one put in vertical beams so that you have no gap? I've been racking my brains trying to think of how you do it. The main bearer beam has to be jacked up onto the existing joists so as to take the weight, but then how do you put in the column beams so that they sit and are fixed to a reinforced concrete pad and so as to leave no gap between the end and the UB? Do you have to use some type of spacers? I would assume that one cannot leave even 1mm gap because that would cause the house to ever so slightly drop when the jack pressure was removed which could cause cracks. I'm just really curious as to how one does it

Originally Posted by Farmer Geoff

I did an under house dig several years ago and with the benefit of hindsight, now know what I should have done differently:

.get plans approved so that the later unforeseen sale of the house didn't involve reducing the price to compensate for work unapproved by council.

.get definite blessing of spouse/partner since she had to do more housework/child caring and less socialising with me and others while I self importantly tended to my obsession.

.understand that friends and neighbours who are initially bemused and appear supportive, may well change their mind, especially if they seek and then fail to get official approval for their comparable silly ideas!

Overall I was happy enough but everyone else grew increasingly irritated!

Once I have spoken with the Engineer and found out what feasible and what is not, then I will look at getting further plans together. We may incorporate a couple of rooms elsewhere (nothing to do with what I'm doing with the digging) but we would rather go to council once than pay their fee's again. But that is really good advise actually. If something happens to me, then I don't want my family out of pocket due to a forced sale at a reduced price

The spouse just wants to know that the house will not fall down. She grew up with a father that built his house from scratch and she lived at home for many a year in a house where building related jobs were always in progress. In this regard I'm a lucky man

I told the kids I want to build them a science lab underneath, which is true, I do want some of the space to be used as a science lab and I want some of it to become a computer server room as well and other storage functions

Lots of visits to my neighbors over the next few years will be in order. A neighbor across the road does mechanical work in his garage so the neighborhood are accustomed to something always happening, wether that be a grinder going or hearing a compressor operating. A jack hammer whacking hard rock is another matter though, I'll have to play some good politicis

A good neighborhood really is a godsend - I hear some horror stories about some people's neighbors

Originally Posted by SabreOne

Holy Cr*p

Can I get a dose of your enthusiasm! There has to be an easier way. ?....

I'm sure there is but they seem to revolve around paying someone else for their time

Doing things myself as much as possible is the only way I could even contemplate doing this job

But I've yet to check out the house lifting fully it seems - some one posted that it may not be as expensive as I first thought it would be (and hence why I dismissed it)

Originally Posted by Marc

I admire your enthusiasm, but digging under a house without a plan is not the best way to go about it. Have you thought how to underpin the house? How to get the additional steel beams inside, props, post? There are a couple of threads about digging under the house, and they look like a very expensive way to make an additional room. It is possible, it is costly and it needs a plan by an engineer. The digging is in fact the easiest part. Everything else is harder.

If I could get someone to do the work for free I'd be a happy man

It all comes down to what can I do myself so as to make it as cheap a job as possible

Lifting a house I cannot do myself. Putting an extension on top I cannot do myself

Putting on extra room outwards I cannot do myself

Digging out underneath I can do most of it myself and as I do not need to pay myself, this is where I can generate the most savings from

If there was another way that was cheaper in the long run that takes account my time doesn't have to be paid for, I'd be onto it quick smart...

Originally Posted by phild01

I would like to know how well the Dexpan goes as well. I have the ironstone type of sandstone and I am a little over with the jackhammering. Mind you I only have about 2 cubic metres to go.

I will not be trying the Dexpan until after I have spoken with the Engineer

The reason being is that if I go the Dexpan route, I will need to buy a rotary hammer and the size required will be upwards of $800+

If the engineer says everything I'm doing is a goer with no hidden extreme costs later on, then I'll buy the drill and the Dexpan and give it a go and I'll post the results up

Originally Posted by PlatypusGardens

In the nicest possible way:

You're nuts

lol

Yeah, I've known that for a long time but what can I do about it?
I'll post more as things progress (but don't expect much, I'm not going hell for leather trying to finish it) and if you hear nothing for a while, it means I've died from it all

Strategic, progressive and early placement/support of the Steel before excavating would simplify the operation but getting that rock out, you will need to go hell for leather!
Do agree with PG, not so much text.

Ok to all the doubters this has type of work has been done before, namely by myself. Covering an area from memory of approx 5 x 6m, depth varied from 0.5 to 1.5m. But I didnt have as much rock instead very hard clay. I started off with plans and Council approval. You will need approval because it is structural. (If you have ok, haven't read all the postings in detail yet).
The Council Inspector had witnessed a house where the external wall was on the brink of collapsing into the hole. Thats a Big OPPS.
I used accro props to support the bearers so that a pier could be supported and safely removed. I checked with an Engineer and he was ok with me excavating under the existing foundations BUT only one meter cut outs at a time, then form up and fill with concrete. He actually wanted the last 25mm at the top ram filled with a drier mix the next day because to cover for concrete shrinkage. Seriously that was a bit over the top because for the volume and height of the concrete the shrinkage would be only a couple of mm. I didnt want to lose too much floor area. I worked along two opposite walls at once this allowed if necessary for the placing of one RSJ at a time.
I ordered in 3 x 300 mm x 6 meter "I" beams. I couldnt even budge one end so I organised a BBQ lunch and invited 6 friends around. We carried the beams between our legs and took them under the house. We all lifted one end at a time onto steel builders scaffold set at the lowest height. Then again lifted each end individually whilst one lifted up the scaffold up a position or two and replaced the pin. When we got the beam as close to the floor bearers we lifted it the last bit with an accro jack, BUT left the end scaffold in place. Started at 8am , done by 10am. Had to get more beer. In your case I would possibly only do 1 beam at a time because you will need too many accro jacks. The end result was very satisfying

I did this into rock but about 18tonne removed from an area of 4.8 x 4m and installed 2, 150mm steel beams but only had to go down 600mm at the deepest point. I felt positive about the possible result because the land slope under the front of the house is around 12deg which means only 3 cut walls created. If you are digging down and creating 4 walls then it will be very difficult to keep water out. The jackhammer has it's uses but with a core drill including a 500mm extension you can 'stitch' drill up to 900mm deep and pull out largish blocks. Other option is a masonry cutting electric chainsaw.

Originally Posted by Marc

You are stating the obvious but missing the point.
If you dig under the house, you will make the piers unstable. If you want to make room for anything that is remotely useful you will have to eliminate some of the piers and replace them with long steel beam and reinforced long steel post at each end. This is an expensive and difficult job that requires access under the house with lifting equipment not to mention the long beams and piers themselves. There is nothing new in what you are doing, the only thing new is that you are putting the cart before the horse.
It is not a matter of digging, it is a matter of planing how big the room is going to be, how many piers need to go and how are you going to replace them, size of beam and piers, plan, council approval and if after that you have the money necessary to do it then only then you start digging.

I've mentioned elsewhere that I plan on removing the piers by placing a number of beams so that they can be removed (this is the ultimate wish, pending an Engineers report of course). The size is fairly well set in that it will be as big as I can go depending on a couple of factors which the structural engineer will hopefully be able to guide me on. I've already decided to cut the length shorter because the cost of moving plumbing isn't worth it

I've discussed it partially with someone else who does building work in the area I live in and he's worked on similar projects where based on the soil (read 100% rock) I am sitting on, he's seen larger projects where they dug right up alongside the footings in excavations. I have deliberately kept away from the footings a set distance and from the piers also until I get specific advise from the structural engineer as to how close specifically I can go.
I have zero soil under my house, the original home when it was build was for some reason excavated down to rock everywhere and then the piers were laid onto the rock. I understand (well, have a concept of) that I need 2 or 3 beams of an unknown size and some column supports at each end. I am also assuming that I will need to dig down and place those columns on a concrete pad with reinforcing to ensure they can hold up the beams and the house (It's could be debatable about the reinforcing but I'll go with whatever the engineer specifies and recommends)

The digging needs to be done anyhow, whether I later opt for removing the piers assuming the structural engineer I am getting in for advice tells me the overall project is worth it, the only variation then will be how deep I go. If the engineer gives their nod of approval I will go down as far as required to make it habitable, if not, I will only dig down a small way so that I can at least get under there without hitting my head on the sub-floor structures which has annoyed me over the past 20+ years to the point where I have decided to act and do something about it

Originally Posted by PlatypusGardens

Too much text for this time of day...

Tell me again why you won't consider lifting the house?
Budget?



Spending a bit of money VS busting your backside over a couple of years doing something which might not work, might damage the house and (worst case scenario) even kill you if something goes wrong.....

Hmm.

When I looked at lifting the costs looked expensive (but I never got actual quotes). Searching in lots of forums etc it seemed people paid around 50K - 80K++ to lift their homes

I don't have 50K to sink into lifting my house, I need to minimise the amount of work I get others to do in favor of me doing the work where possible, so I pretty well dismissed lifting

Also, the wife doesn't want a pure 2 story home, bad knee's from many years of snow skiing has seen to this idea being also shot down

Hopefully a structural engineer knows what he's on about and gives me the right advise so that it doesn't fall down, otherwise my kids can sue them for bad advise (because I won't be here to worry about it) lol. (not that I'm a litigious type of person, don't really have time for those types of people quite frankly)

On top of this, I live in a bushfire flame zone. We got someone in last week to give us ideas on extensions elsewhere and he basically told us that there is currently a Nazi women assessor at present in council who is making him jump through hoops for flame zone compliance. If I lift my house, then it is likely the council will deem the renovation as affecting the whole house so all of it will be forced to be upgrade to flame zone compliance. That is an expense I don't want to have

If I dig out underneath, then I will not be exposing any of the new area to direct flame attack so flame zone compliance will probably be avoided or at least greatly cost reduced (this is my hope at least based on the non-committal advise of the building planner we got in)

Originally Posted by thegableman

Ok to all the doubters this has type of work has been done before, namely by myself. Covering an area from memory of approx 5 x 6m, depth varied from 0.5 to 1.5m. But I didnt have as much rock instead very hard clay. I started off with plans and Council approval. You will need approval because it is structural. (If you have ok, haven't read all the postings in detail yet).
The Council Inspector had witnessed a house where the external wall was on the brink of collapsing into the hole. Thats a Big OPPS.
I used accro props to support the bearers so that a pier could be supported and safely removed. I checked with an Engineer and he was ok with me excavating under the existing foundations BUT only one meter cut outs at a time, then form up and fill with concrete. He actually wanted the last 25mm at the top ram filled with a drier mix the next day because to cover for concrete shrinkage. Seriously that was a bit over the top because for the volume and height of the concrete the shrinkage would be only a couple of mm. I didnt want to lose too much floor area. I worked along two opposite walls at once this allowed if necessary for the placing of one RSJ at a time.
I ordered in 3 x 300 mm x 6 meter "I" beams. I couldnt even budge one end so I organised a BBQ lunch and invited 6 friends around. We carried the beams between our legs and took them under the house. We all lifted one end at a time onto steel builders scaffold set at the lowest height. Then again lifted each end individually whilst one lifted up the scaffold up a position or two and replaced the pin. When we got the beam as close to the floor bearers we lifted it the last bit with an accro jack, BUT left the end scaffold in place. Started at 8am , done by 10am. Had to get more beer. In your case I would possibly only do 1 beam at a time because you will need too many accro jacks. The end result was very satisfying

Thank you!!!

You have described what I have found in countless youtube video watching of similar operations being performed

https://www.youtube.com/watch?v=lkxAIsCECbI

This video shows an underpinning operation, there are other better one's of this same building project but it shows that they mark the walls off in 1-2-3 numbering sequence and dig out every 3rd one at a time and fill it in so that there is a minimum of 2m between each underpin workings at a given time

I initially thought of underpinning but that will add extra work and work that I would not be confident in doing myself. I could ask my father-in-law, he's a retired builder but because I'm on 100% rock, digging out under the footings and back filling with reinforced concrete seems like I might be left with a weaker structure than I already have, so I'm thinking of putting concrete blocks against the footings (assuming I am allowed to dig right up against them) and putting a galvanized rods down in them and filling them with concrete - I'll take the engineers specific advise on this however

Those beams are bigger than what I thought I'd need (but I have taken a totally wild guess anyhow just to get a ballpark figure). 3 x 300mm would be an 310UB32.0 ? At 6m that would weigh 192kg's. With 6 blocks that's still 32kg's of weight to move each!

Because I didn't know beam sizes, I guessed at needing a 250UB31.4, The span length would be 9m, possibly slightly less, I have only measured from outside, not from underneath the house. Based on your situation my loose rough guess may have been somewhat lean

I am making an assumption that I can replace the existing bearers directly with a universal beam in a 1:1 swap-out. Big assumption I know, that is why I am getting an engineer in.
For columns I figured some 150 UC37.2's but again, I am making a decision with the same precision as throwing darts at a dart board blindfolded!
Depending on what the engineer says is feasible, I may need 3 beams and supporting columns or 2 if I cannot go as far as I would like

I must have watched over 200+ youtube videos on house lifting, house dig outs, beam installation, jack hammering and rock excavation etc etc etc. I've even got prices on buying acro's and figuring out what length one's I would probably have to purchase (but I admit I have not calculated how many I would need). I've found an excellent site for learning about building (cert 4 in building course, free too! that I have been going through)

Before I came to this site I have been looking at this on/off and getting knowledged up for probably 8 months now. I've looked at under house dig-outs for more than a year as well. Over the past 5 years I have been casually looking at building work on youtube, looking at building sites etc

Anyhow, the beam lifting part I really appreciate. This will be something I'm going to have to get help in for. My neighbor handles building projects, I may end up hiring his workers for a day to get the beam up and into place when that stage arrives (all pending on an engineers report)

This whole thread was to find out what types of things I should factor in, what to watch out for etc. Some of the advise, such as yours, has been really helpful and confirms a lot of what I have researched but there's always extra tid-bits and gold nuggets buried within people's posts such as yours that outline practical elements of how to actually go about stuff. Thanks for posting what you did, it was really helpful

p.s.
When you lifted the beams in place, how did you do the columns?
I'm at a loss to think about how the columns are put in so as to leave no gap between them and the new beam
i.e. If you do a concrete pad, put in the column and then put the beam on top, you will either have a very small gap to allow for the beam to be slid into place OR you need to have the column in place and bring the beam in and lift the house a few mm higher to slide the new beam in and then let the house down onto the beam

Either way to me seems to involve either slightly lowering the house or listing the house which in my mind could result in tiny cracks?

Would you mind describing how you did the beam inserting please?

Originally Posted by PlatypusGardens

Supporting while digging and replacing piers is one thing.
Pretty sure this guy was talking about digging around and leaving the piers in place.


Which is why we're being doubters.

Almost correct, except the time sequence and final desired result is slightly different

I am digging out around the piers, yes, but for starters, but I am keeping away from them until I get an engineers report to say how close I can actually go

I am also limiting how far down I go for the same reason - this I want to do irrespective of the final result

Eventually, the piers will be replaced by beams, assuming the engineer says the whole project is feasible

It's like this...(remembering, I am on 100% rock, the only soil under my house is dust, everything else is rock)

1. Dig around piers (keep away from them about 200mm) and dig down a certain depth (keep a slope outwards from the piers)
Keep away about 250mm from footings

This dig-out work I want to do for easier storage access anyhow, I'm sick of getting sore knees and whacking my head under the house every time I go under there

2. If Engineer says 'Keep going, this is feasible), then keep digging as per his instructions

If Engineer says 'Mate, give it up', then dig out as per his recommendations for not replacing the piers

Assuming Engineer says go for it
3. Dig out and replace piers with beams, enjoy extra space fully

Originally Posted by Outdamnspot!

I did this into rock but about 18tonne removed from an area of 4.8 x 4m and installed 2, 150mm steel beams but only had to go down 600mm at the deepest point. I felt positive about the possible result because the land slope under the front of the house is around 12deg which means only 3 cut walls created. If you are digging down and creating 4 walls then it will be very difficult to keep water out. The jackhammer has it's uses but with a core drill including a 500mm extension you can 'stitch' drill up to 900mm deep and pull out largish blocks. Other option is a masonry cutting electric chainsaw.

Because of how they originally built my place, there would be about a 5 degree's of slope under the house. The land slopes from front of property to the back and from left to right (if facing the property). Where I started to dig was stupidly at the lowest point but it's also the highest point in terms of access

There does not seem to be any sub rock water flow that I can tell. My plan is to concrete block it all and water-proof. Part of what I want is to have a bush-fire safe area to escape to should I not get time to evacuate in an emergency (I have no desire to defend my home in a bush fire situation but if I cannot get out I want a safe place to retreat my family to if possible)

150mm beams for a 4.8m span?

Just past my building, the land falls away and about 10m past that it virtually drops off the end of the earth. I am thinking of running sub floor water piping to this point to get any water away. My intention is of course to stop any water at the high side of the land first and channel it away to the edge rather than let it get underneath in the first place. Water and how to deal with it is probably the least amount of research I have done actually, sounds like I had better get my learning hat on (I saw one video where they put in all sorts of damp layers, waterproofing, gravel and even marine plywood to ensure no water or dampness came up)

I have already worn out one bull point chisel and the second one is showing signs of some wear also. Tonight I discovered that slicing at a 45 degree angle across a cut face produces good results, that was until my faithful, 20 year old flood light's globe decided to blow. Can't complain at getting 20 years out of it ). I'm learning better hammering technique as I go, and I do enjoy learning new things actually

That core drill idea is interesting, very interesting. I was looking at getting a rotary hammer drill (DH45MR - 45mm SDS Max Rotary Hammer) but I am still looking at what specific model to buy, I believe this size will handle the drilling needed if I decide later to go the Dexpan route (chemical breaker). I know it supports core drill bits but I don't know to what size core drill bit it will go up to

The masonry saw would be a last resort, I can come at buying a rotary hammer drill because I can use it later but a masonry saw I would have no further use of. Also, I'd need to deal with all the water used to keep the blade cool (although I have seen video's of dry cutting) and I'm not ready to handle large volumes of water just yet - let's see how I go as time goes on and as the body starts to complain about the workload )

Thanks heaps for the advice, much appreciated

Not a huge amount of progress made this week so I have not bothered taking any additional photo's, maybe in a month when I might have made some visible progress and have more time to dig

As a person with long-term (uncompensated) RSI, all I can say is stop and think about what you are doing to your body.

Human bodies are not designed for this sort of thing.

Arron

STOP. Get a geotechnical engineer now. You need their advice and a structural engineers. Geotech covers the bits below the piers and how it holds together and takes load. The structural does the bits made by people above the natural ground. You tube will not suffice for your needs.

I joined this website just to see your thumbnails. https://www.youtube.com/watch?v=6bvowiyc85U start from about 9:30 ;-)