Thread: New piers..brick or steel

I found someone to have a look at my wood framed cottage which needed floors relevelled. The original idea was to "jack and pack" the brick piers but a few hours into the job the re level guys rang me to say that as they packed the piers the house would simply resettle and push the brick piers further into the ground. This was due to the "dry sandy nature" of the soil with the piers apparently "literally sinking back into the dirt, visibly moving down". This was "worst case scenario" meaning a simple jack and pack would not cut it. So the advice was to replace a number of piers, concrete in underneath them and do it properly. I'm OK with this if its whats required and have been offered the option of brick or steel piers. Are there advantages/disadvantages with each option? The costs will be the same. What would you recommend?

Thanks

I would be going for steel
I think they would be easier to install in that situation as well.

Regards Bradford

I didn't even know bricks would be used as a 'professional' option these days. I thought they were more makeshift solutions? Maybe it's an option to keep in line with existing?

Anyway, if there' the same price, I agree with Bradford, go steel.

What about concrete stumps? Aren't they cheaper? Perhaps though the installation is harder?

Thankyou Bradford and Cooky for your replies and advice. I guess I'll go the steel option. Regards the sinking of the original piers does the scenario described sound reasonable to you? That is, how come the piers would sink (further?) into the ground once packed? I just can't quite get my head around how/why thats happening. Can someone please explain it to me?
Cheers

bearing capacity of the soil is exceeded by the load.

If the house has been there for some time it does seem strange that they would sink now.

Regards Bradford

Yeah it is strange it's sinking like that. When I stumped my house that happened, but it was because rather than a concrete pad, they used a 'redgum pad'! An offcut laid horizontally, and then the stump on top of that. Of course the flat piece had rotted like a banana! I've been told that was common practice a few decades ago.

So if it's your soil straight under the stump, it's weird to be moving. Pulse is right about the load exceeding, but sand tends to move straight away unlike clay which often takes time, so at installation it should have moved then.

Oh well, conditions change and sometimes you'll never know why. A concrete pad will make a huge difference, cos the load is spread to a much larger area, incorporating more of your sandy soil to bear the weight.

BTW, the reason they gave for the stumps moving - "dry sandy nature" - I don't reckon is good enough. Being dry and sandy doesn't necessarily mean it'll move, to me that sounds like a lazy excuse. Perhaps they just didn't bore you with details, but if it were me I would actually want the details.

Maybe check that they've dug down to the bottom of the stump and seen exactly what is happening.

yeah but how come the piers move further down? Pulse would you mind expanding on the bearing capacity answer? The piers themselves were not moved as the bearers were jacked up and the space between packed. So how come they drop even further, straight away, than they've done in the last 60 years. I just can't get my head around the physics of it which is confusing and frustrating. What am I missing here?
Thanks again

My guess is this:

When a stump sinks, the bearer it holds will move down with it only to a point. The point at which the bearer stops moving, is when that bearer is transferring most of the floor/roof/wall loads to other stumps nearby. So the bearer is under more strain, and nearby stumps have picked up more loads. Remember that loads will always find its way down to the ground (not always gonna be a straight line!) and all the structural elements move around a bit, share loads together, bla bla, until 'equilibrium' or a balance is reached. When a balance cannot be reached then failure occurs. An example of an imbalance might be your bearer that transferrs some of the loads to nearby stumps - if these loads exceeds it's capacity, then kasnap.

So...when you jack and pack, the bearer is now raised up and the small deflection that had occurred is taken away, thus the full loads are back on the dodgy stump. The soil can't take it so it sinks further, until the position as previous is reached and the 'balance' is returned.

Cheers

Hey Cooky,

I like it. Excellent response. makes sense. I had a light bulb moment. Thanks heaps

Does anyone know the going rate for pier replacement? About a meter of space in the subfloor and I've been quoted $350 per pier with 14 piers recommended to be replaced.
Does this sound reasonable?
Many thanks

Spot on cooky,

I'm repiering at the moment, when I'm lazy and use a small sole plate for the jack it just sinks in with every pump of the jack. When I use a large sole plate it sinks a bit initially but then I'm able to jack the house, and hence remove some load from the adjacent stumps.

My place had concrete stumps sitting on sand, or on a couple of bricks, by comparison I'm using steel stumps on a 450mm circular concrete pad, massive increase in bearing capacity.

Pulse

Thanks Cooky, Bradford and Pulse for your replies. I feel much better about the process and far more informed. It seems that the underpinning guys are (wait for it..) on the level (ha ha I'm "crackin" myself up), with their recommendations.
Cheers

So I went ahead with the new piers. I'm really pleased that I did. They are brick (not steel) as average height was probably less than a metre so easier to build up bricks. They are the same as existing which I like. I spoke to someone who new the area and his take on it was this. As I live slightly down hill from a number of new MacMansions the water that used to run through the ground and under the house was diverted due to swimming pools etc. As a result the ground could be "like an Aero bar". Eventually had a number of new piers with the concrete going in as deep as 800mm in some of the holes. They underpin guys dug through loads of really sanding stuff to hit hard ground to ly the concrete on. The floors are not perfectly straight, but they are much much better. I didn't want bathroom tiles cracking etc but it's much more solid, no squeaks or bounces at all. Some minor cracking around picture rails and skirting but no dramas and easily filled when I need to paint. I was charged $350 a stump and they even threw in a supporting beam that went in under a load bearing wall.

Originally Posted by Pulse

Spot on cooky,

I'm repiering at the moment, when I'm lazy and use a small sole plate for the jack it just sinks in with every pump of the jack. When I use a large sole plate it sinks a bit initially but then I'm able to jack the house, and hence remove some load from the adjacent stumps.

My place had concrete stumps sitting on sand, or on a couple of bricks, by comparison I'm using steel stumps on a 450mm circular concrete pad, massive increase in bearing capacity.

Pulse

At the risk of thread jacking tomato_brine I was curious, Pulse, what material you use for a sole plate and what dimension you call large ie 1' x 1'? I am looking to jack and pack use a bottle jack, the bearers are very close to the ground in my case.

I just use a treated pine offcut 190 wide maybe 450 long. If there isn't much clearance I just dig it lower... Lowers the risk of collapsing into the pier hole too.

Cheers
pulse