Our slab seems to have severe cracks after the recent rain.

[wylie]

After the recent very prolonged rain, our downstairs carpet got very wet. We dried it using a couple of fans, and though it seemed dry, there was a musty, damp smell which wasn't getting any less obvious as the days continued. Concerned that the underlay and/or slab were still wet, I called our insurer today and got a claim number, though it was not at that stage called a "claim".

I told the lady that we would pull up a bit of carpet to see what was happening under the carpet.

We did that this afternoon and were not so surprised to find several cracks in the slab. It is almost like the corner has "cracked off". There are cracks on the diagonal plus a large crack along the area where the drainage pipe runs through the slab taking water from the drain behind the solid core filled besser block wall.

I have taken photos and here are a couple. The first one is one of the cracks that run diagonally across the floor at the front corner of the slab, running roughly from the side across the corner to the front of the house. I think the corner of the slab has broken off. Outside this room the ground was so sodden that my son stepped on a garden bed and sunk to his ankle.



The second photo shows a long split where it is very dark. There is a drainage pipe running from back to front under (or as part of) the slab and I think this might be a weak point, though it was engineered, checked and passed as the build progressed.




The upstairs of the house is held up by steel posts and there are no cracks in walls or ceiling. The water has come up through the slab, through these cracks.

We have a $500 excess. We are happy to rip up the carpet. Whether we claim this on insurance will depend on how much it costs to recarpet, but also on how much it costs to stop water coming up next time we get a lot of rain. My concern is that whatever we put down, carpet, floating floor or tiles will be going onto a slab that will allow water up in the next big wet.

We've had this slab for about 12 years, had water through from the rear where the earth is dug out, years ago, but hubby has done extensive extra drainage. This is the first time we have had water come up through the slab, and I do worry that the slab might be compromised (and subsequently cracked) after the ground was so sodden just recently.

Does anybody know what it is likely that we need to do to fix this? Is there a waterproof membrane that we could paint on, or is this problem needing more than a membrane to stop water coming up again.

 

[wylie]

Showed this question and post to hubby and he says his thought is that we may have to dig out the cracks and fill with some sort of waterproof filler. There are quite a number of cracks and the second photo showing the line that we believe follows the drainage pipe possibly runs through to the back.

We have a pool table, couch, heavy coffee table and TV stand blocking us from pulling the carpet back further and want to leave it until the assessor sees it.

The assessor will no doubt will give us his opinion and advice, but I would like to be armed with a bit of knowledge before he gets here. I'm also wary that he might say "those cracks were probably there ten years ago" which just isn't so, though I cannot prove it.

 

[NBS]

Hard to say with this photo howver I dare say the crack has been there for some time. The fact your son sank to his ankles outside the place sort of indicates a lot of moisture in that location, of course plenty of moisture everywhere in Sth East Qld at the moment. With my place receiving about 400mm.

With the ground is so wet and around your foundations, this is never a good thing. Depending on your soil type the building may have moved because of the amount of rain we have been having. You may need an engineer to check your slab out.

Of more importance is the water coming up via the crack this would seem to indicate poor installation of the plastic membrane under the slab or nil installed. Nil installed does not seem to be the case as you did indicate it was passed.

While there are products that can be used to inject into the crack then seal over the total floor to help prevent the water entry you need to first find out, why! its happening.

You may need to look at more drainage to ensure excess water drains away from your foundations.

As for your insurance Co hmmm I would like to know this outcome.

There are a few things you could try to work out if the place has moved. Would put up but I'm to tired to type any more so going to bed. PM me and I will help where I can.

Thanks
Brian

 

[battler]

There is a drainage pipe running from back to front under (or as part of) the slab and I think this might be a weak point, though it was engineered, checked and passed as the build progressed.

This is where I'd be looking first, the pipe may have cracked from movement, but also any surface water can sometimes follow the path of the pipe (outside the pipe) in the trench it was laid in.

Does anybody know what it is likely that we need to do to fix this? Is there a waterproof membrane that we could paint on, or is this problem needing more than a membrane to stop water coming up again.

I think you have to look at the retaining wall drainage first.

The membrane should be under the slab so it stays dry, putting waterproofing on top means the slab and ground will be constantly changing from wet to dry, which leads to movement and usually cracking.

 

[The Fence]

Agree with battler, re-direct the source of water innundation, then plug the cracks.

The slab should not have cracked and the engineering may be right but the execution ( slab pour) was obviously wrong. Steel may have not been chaired up properly and that pipe not enough concrete cover etc....

redirect that water and should be ok.

GL

 

[wylie]

Thanks for the replies. The drainage behind the lower floor is good, as hubby has worked on it for a long time. We only ever had water in once and that was after a massive amount of rain and it filled the drains and backed up behind the core filled wall, possibly seeping in where the besser blocks joined the slab. After that, hubby has done a lot of extra drainage, lowered the level of the drain behind that wall, and cut through the rock at the back corner and opened a hole at the base of the 8 foot retaining wall outside the house, so that water now cannot pool behind the besser wall, but runs straight to the side of the house, down a spoon drain, into another drain that takes it to the street.

As we are on the side of a hill, the water does sometimes pour down that spoon drain, so our yard at that corner does get wet, but only when we have had rain falling for days, like just happened.

We are sitting on rock. We had several days with a rockbreaker in the digging out under our house (and our pool). The only place there is any soil is in the yard at this corner of the house, but it is not deep. Coorparoo is well known for its rocks .

If those cracks have indeed been there for a while, my concern is that with the ground so wet for so long recently this corner of the slab may have moved as this corner is the only bit of our block with ANY soil on it deeper than about six inches.

Anyway, we will await the assessor. Drainage really is sorted and works very well (except possibly that pipe under the slab which may be a weak point). I have all the documentation and will get it out so we can go back over what was done and show the assessor. I also have photos somewhere as each stage was carried out (just have to find them).

Is it advisable if he just says "it's okay - just recarpet", that we pay for an engineer to look at this? We plan on being here for the long term, and also need to be able to pass a building inspection if we sell and I know (from experience) that any question about drainage will be a big stumbling block for any prospective purchaser.

 

[Sunfish]

My house sounds similar. It's split level with much of it on steel posts.

During the wet last year I had a slab poured under the main house and then enclosed. The builder went to a LOT of trouble to ensure proper drainage. It was a real problem because water seeped into the back yard off the hill behind, for weeks after Cyclone Yasi.

I mention this because I agree that you must solve the drainage first.

Edit: Reading further, we have MUCH in common. If you have a rock substrate the water seeps downhill for ages and keeps these small bits of soil sodden. I used the sides of an old water bed as planks to the clothes line because that part of the back yard had constant water laying in it.

 

[The Fence]

You need several opinions on site.

 

[wylie]

Insurance assessor just called, took stacks of photos, looked at our pit behind the core filled wall, listened as we explained the extra drainage we have done.

She gave no commitment except to send a builder around to take a look. She had said we could rip up the carpet, but we thought we would leave it in place for her to see it. Hubby is ripping it out now, thank goodness, it stinks.

Assessor said that if it is decided this is seepage we will not be covered. I explained that my major concern is that whatever we put down in place of the carpet will get wet again due to the cracks in the slab.

I have all the documentation, including the drawings showing the membrane. It is clear that one major crack runs along the line of the drainage pipe. I can only assume that this is a weak point and that the corner that has diagonal cracks has dropped enough to crack the slab and the membrane, allowing water to seep upwards.

If they call it seepage, we plan on bringing in the engineer who drew up the plans for the slab to take a look. Seepage after 14 years of no seepage has to be caused by something happening to the slab... surely.

If we can fix this cheaply, then I'm happy, but if it means our slab is compromised and the fix is more expensive then I will be looking at it being covered. From the PDS I'm thinking that the cracking of the slab caused by the massive amount of rain we copped should be insured. We shall wait and see.

I will report what happens as it happens...

 

[wylie]

Hubby ripped up the carpet and we have found cracks all through the floor, with two leading under the walls that were added on top of the carpet when we created a fourth bedroom downstairs. It looks like we must rip up the carpet in this bedroom as we are worried that if the cracks head under the wall into this room, then the carpet in that room must also be mouldy.

I'm hoping that this is insured and the insurer doesn't try to say that this just falls under "seepage". Our slab was never cracked like this when it was passed, but we don't have any photos to prove it.

 

[AlmostBob]

just in case,
get a plumber who has one of the pipe cameras to scope the pipe, cracking around the pipe could include the pipe, and be a lot more water to come

 

[marg4000]

From the photos it looks like either the slab wasn't laid properly or the specifications were incorrect and the slab was not thick enough.

I would suspect faulty workmanship which may or may not be covered by insurance.
Marag

 

[Pa1nter]

I doubt it would be covered by insurance,I see cracks like this all the time in new homes and worse.

I also see the moisture in new houses that they just tile over

One very expensive Toowoomba builder a couple of years ago had a constant slight pool of water in the lounge room that wouldn't dry up.
I saw it while I was painting the house over two weeks and I saw it one month later.
I think NBS is right,plastic under the concrete compromised during build.

 

[Ocean Architect]

Just a quick reminder that I work as a builder cos I havn't been around for a few months and people might not remember that. I'll take you through my thought process step by step and justify each thought.

Waterproof membrane is intended to stop moisture seeping through concrete, because concrete is porous and will slowly allow small amounts of water through without a membrane. If the membrane was faulty or not installed at all, you would experience prolonged damp of the concrete. Now the fact of the matter is that the slab has been there for 12 years and this is the first time you've had the problem, which means that it is more likely that something has changed recently, and likely, that something is not the waterproof membrane.

Second, you have to figure out 2 things - where is the water coming from, and why is the concrete cracked. This might get tricky, because either of those things will cause the second ie lots of water compromising ground integrity will crack concrete, and also, cracked concrete will allow water in, or may have cracked a water pipe (not drain - pipe) which means that water will spurt out of the cracked pipe all over the place.

So, going through it logically:

If the water got there first, the question is how it got there. It can do that through a cracked pipe, poor drainage, weather, or a combination of all 3 (ie bad weather means lots of water which compromises the ground which cracks the concrete which cracks a water pipe which means more water).

So with this in mind, the most important and obvious thing to do is check your water meter/water bill. If your water meter is showing ungodly amounts of water usage, you have a cracked pipe end of story. (I know this because *I* had a cracked pipe, and used $5000 worth of water in 4 months. I then cried 5000 tears in 4 minutes)

Second, you need structural assessment of the concrete slab to find out why the heck it cracked. If it was bad weather and the slab cracked in a short span of time, you may have an insurance claim to make. If it was poor ground quality and the slab cracked over a long period of time, then unfortunately there is little you can do because a builder is only liable for that sort of thing for 7 years.

I suppose in that case you could chase the engineer, but its a costly lengthy process and probably not in your interest unless the whole house fell down on someones ferrari and they were suing you.

So yeah, that's enough info for now. Let us know how it goes