Thread: Wet and muddy under house

Hi guy's I'm new to the forum so I hope this is the right place for this.
my house is on a sloping block with the garage underneath. At the back of the garage the previous owners have cut into the hill. I think as a consequence when we started finally getting rain again the soil started collapsing and is rapidly getting closer to our footings. It has made the back of the garage permanently muddy and tends to pool with stagnant smelling water. After speaking to a number of builders and brikkies the general consensus seems to be to run ag pipe across the back of the house with or without a retaining wall to gain depth on the block which we would also use to put a deck put the back. I'm not completely sold that this will fix the problem and any advice will be greatly appreciated.
Cheers, sakas

'Ag pipe' sounds simple - the fix is to get the water away from the back of the house so you will need to install a drain to do that. As well as a suitable sized socked ag pipe it will need aggregate and to be sloped correctly - and you need to be sure that the water ends up where it can run to storm water system - into the pipe system or the road gutters etc - and not simply move the problem to somewhere else in your yard or your neighbours!

So how deep are we talking with the drain and I am assuming ( which I know is dangerous ) that the drain would run along the back wall of the house to a sump.
I had every intention of burrying a socked 100mm ag pipe under 50% aggregate, 300mm gap behind the wall then top fill with soil and slope it out to the side of the block into the storm water/ gutter.
Thanks for the reply to, any advice is much appreciated and I will only take it as advice.

Cheers

I thought I might these pics so as to see if this helps to give people a better idea of whats going on. As can be seen we have just had quite a bit of rain over the past couople of days and it's now a complete bog. Things are getting desperate and I need to get into this project ASAP.


The cut out was done by the previous owners and the RHS post added in. Although it looks like it's leaning in the photo it's dead straight and very solid in the ground. Myself and another mate had a go at it and there is no movement at all.

Looking at that RHS post you have more than just drainage to worry about. A single picture does not tell enough, but that excavation is unsafe in any case - perhaps it's just the pic, but it looks like there is footing that has been exposed. The work to make this right is non-trivial and not simply drainage - although you have to do that too. Take more pics and maybe we can help. Not suer what you mean by draining to a sump - you need to capture the water and direct it ways from the underneath of the house, but the way that excavation has been done it will take more than work on the outer upper wall to fix what is happening there.

Originally Posted by Bloss

Looking at that RHS post you have more than just drainage to worry about. A single picture does not tell enough, but that excavation is unsafe in any case - perhaps it's just the pic, but it looks like there is footing that has been exposed. The work to make this right is non-trivial and not simply drainage - although you have to do that too. Take more pics and maybe we can help. Not suer what you mean by draining to a sump - you need to capture the water and direct it ways from the underneath of the house, but the way that excavation has been done it will take more than work on the outer upper wall to fix what is happening there.

Ok so here some more history on the house.
The previous owners excavated out the back of the garage to cause this disaster that we were advised by the building inspector prior to purchase was not a worry. The RHS post was put in after the excavation as an after thought I'm guessing. The actual original footings up the back still have about 1.5m of original soil in front of them.
Here are some more pics that I hope will help make it a bit clearer.

Well I'd be questioning where that building inspector got his license - I thought they'd stopped handing them out in Wheaties packets . . .

Depends what you expect to achieve. That water will simply be flowing through the sub-soil and because the area is clay is simply pools on top while we have this continued rain - you don't say where you are in NSW, but in most urban areas on the East coast the soils are saturated so any new rain runs off or pools when it can't drain away - as in your case.

If you want to get that area dry then you'll need to get a drain in along the back and a retaining wall that is waterproofed from the high side ie: the back. To drain that though you'll need to take the water out the sides or towards the front to the storm water drain - that is not a trivial task.

I am more concerned about the structural safety of that situation. I can't believe that steel work is approved - and probable can't be without some major changes and that undercut footing even 1.5m out from those piers is asking for trouble IMO. The problem is that to properly drain and waterproof the area you would need to excavate considerably more to level and square off and to allow depth and with for the drainage trench. The steel upright is plan primed mild steel RHS not galvanise and seems to be sitting in mud - it needs to be cleared and surround by concrete as part of the work too (although my guess is that it is undersize).

I know you do not want to be told this, but you need to get professional engineering advice IMO before you try anything at all. Probably not in danger of any catastrophic failure, but the nature of these things is that they are catastrophic ie: massive and without warning! I repeat my earlier view - the water is the smallest part of your problems and the last one to be fixed because to fix it you need to fix the other stuff first.

I'll second that. Get a competent structural engineer in as soon as possible. No mucking about!

Thanks guys I'll call an engineer Monday and get on it. We're on the NSW Far South Coast

Make sure you report the building inspector won't you! And let us know what happens (we're nosy) and while you have the engineer there, make sure you have all your other engineer-related questions on the back of your hand so you get your money's worth!!

I just read the building inspection report and it was done back in 09 and reads that there are no problems. All comments relating to drainage and ventilation are good and to the building code supposedly. Not sure about reporting them but I will be calling an engineer in the morning as we just had another 15mm of rain just today and can no longer get into back of shed without gum boots.
This is starting to suck.

In 2009 the drought had not broken so water might not have been evident, but that wouldn't make the structural work OK!

Originally Posted by Sakas

I just read the building inspection report and it was done back in 09 and reads that there are no problems.

Was it 09 when you bought the property, i.e could the works have been done between the report and when you purchased?

We purchased in 09 and no work has been done since the report was written, but looking at the building inspection pic's there was a lot more soil there back then and it all looked pretty cool. We have done nothing to the house since we have had it but were planning a while ago to do a retaining wall in there and create a workshop. Then the rain started and we held off as it was so wet in there. As you can see it's been all down hill from there but the last month has been particularly bad.

So latest,
Local structural engineer has been and it's not all gloom and doom.
Structurally under the house beams, posts and footings ect is all good. Looks like the batter that has slipped is now stablised.
We need to run 2 subterrainian drains, one across the back wall of the house just above the footings so as not to wash them out. The other about 1.5m out from that on the water table if we can pick it up. Both of these will be run out to a new drain exiting to the street.
Once we can see that this has stopped the water we will retain the batter with a block wall with more drainage.

The engineers has offered to come out and check all the sub-terrainian drains before I back fill just as part of his service. He has all supplied me with all BCA requirements and drain plans/design. Along with this I'm going to open up the under house vent hole and place new ones acroos the back wall once we have excavated down for the deck.
Feeling much better about it all now.
Best $200 I've spent in a long time.

Good outcome sofar

I am always surprised that people seem frightened to get pro advice for a few hundred bucks when they have spent 10s and hundreds of thousands on their asset! So you've made the right choice - and with that advice you'll be able to do most if not all the work yourself.

Originally Posted by Bloss

I am always surprised that people seem frightened to get pro advice for a few hundred bucks when they have spent 10s and hundreds of thousands on their asset! So you've made the right choice - and with that advice you'll be able to do most if not all the work yourself.

I will always make sure I'm 100% confident with the advice I get and if I have to spend a couple of Hundred when I'm about to outlay Thousands it's good piece of mind.
Thanks everyone for the advice and I'll post as I progress. Except for the excavating and some of the trench work I will be doing the lot myself. One of the boy's at work is a builder and has said if I need any advice just ask.
Fingers crossed I find no nasty surprises when the digging starts.

Great outcome - and what a relief for you! I always feel that a few bucks on an expert is better than messing around where this sort of potential issue arises. Glad it has worked out so well for you!

Can you take a close up of the steel beam and the post connection? that looks a bit dodgy to me.

I have similar problem with one of my rental property. The key is to (a) keep the place dry (so drainage) and (b) making sure the soil does not move, and (c) making sure you have enough support for your house.

Sorry for not posting sooner but there was not much going on except for floods and a river in the back yard. I certainly had not forgotten
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all the advice I was given from all of you.
Well here we are, the rain has finally stopped and the digging has begun.
Today the back got leveled and the sub soil drains went in.
Tomorrow the post for the retaining walls will go in and maybe the rest of the storm water dug.