Cracking in foundation floor

[Kloubek]

Hey guys,

I just spent half an hour looking online for info, but have heard mixed opinions.

We are building a new house, and it is about 2 months from completion. We noticed in the basement, there is a crack about 1/8" from wall to wall smack dab in the middle of the basement. It is not heaving on either side.

When we take possession, we want to build a suite. I know it is normally recommended to wait 1-3 years for any other issues to present themselves, but we really would rather not wait that long if at all possible.

So, bottom line, most sources online say that concrete will often crack while curing; nothing can be done about it. Do any of you experts agree? Are thin cracks from wall to wall nothing to worry about? I should at least get them filled by the builder, no?

[frozenrice]

Cracking is normal. Builder's rule of thumb is if you can slip a loonie in the crack that it needs to be addressed. If it's 1/8" thoguh, you have a case and they should be patching it up. You can mention it to them now. If nothing's done by the time you take possession, make sure they document it on the walkthrough at the least. At least it's on paper.

[bwling]

Same thing happened to me, but the builder would not fix this problem right away as they said that the house is still settling and they would wait for a year. They did come back to fix it as promised after one year.

Just mention to them that you are planning to develop it right away and I'm sure they can do something to help you.

[Kloubek]

I just threw 1/8" out there... it might not actually be that wide - I'm really not sure. But I like the loonie rule - I'll try that.

[barmanjay]

cracking is totally normal.

you can get concrete patch for it

usually cracks will form along underground lines, as the ground will usually settle around them.

[masoncgy]

Builders recommend that homeowners avoid basement developments for 1 year for precisely this reason... slab cracking...

It is rare for a slab NOT to get a crack in it... out of the 100s of homes I turned over while working with a major builder, I believe there was only 1 or 2 that had no cracks in the basement at possession... every other home had one... or more than one... but usually hairline cracks that couldn't even hold filler...

Cracks are not filled until they are wide enough to accept the filler material, which is usually the width of a loonie. As well, unless the cracks are significant in size or indicate a more serious problem (such as heaving), the builder will not fill them until one year has passed.

If you want to proceed with a basement development sooner than later, you can always see if the builder will come and fill in the crack (which is a 50/50 chance) or just proceed anyway. Normal slab cracks pose no risks at all.

[Tik-Tok]

If you HAVE to build a basement suite right away, I'd suggest going with wall paneling instead of drywall. Even if those cracks are fill now, the ground may not be completely settled yet, and new ones could form, OR the old ones re-open.

At least with panels, you can remove them in a couple of years and inspect for cracks and moisture issues.

edit: oops, missed the "floor" part of the OP, but I guess my suggestion still applies, as the walls can still crack.

[Kloubek]

Thanks guys - you've alleviated my concerns.

I will check the crack again to make sure it is not wider than a loonie - it might very well not be. Regardless, I would put down a moisture barrier anyway....

We don't HAVE to build a suite right away, but it would definitely help out on the monthly payments if we did. They gave us an option of pre-finishing the basement themselves (for a large cost, of course), so I figure it CAN be done - you just risk not noticing potential issues.

One thing in our favor is that by the time we seal up the walls and floor in the spring, we will already have melt-off from this winter. That should help alert us to any potential leakage at that time. Of course, if we seal it up at that time, anything from that point on will not be noticed until it is too late...

Mod: Thanks for moving the thread!

[liquidboi69]

I'm not super sure about all the background behind this stuff. I do know that concrete has to be humidified/cured in Calgary since our humidity in the air is so low.

A contractor from the east tried to pave the airport, but the whole thing ended up cracking since they don't have the humidity problem in the east that we do here.

So if it is because your builder was uninformed about that, you should try to do something about it.

Another thing is that most houses have 1-2 years of warranty post construction where the project manager is liable to replace/patch anything that is substantial.

I don't have personal experience with any of this FYI. These are just things I learned in school...so take it for what it's worth.

[barmanjay]

foundation walls aren't really an issue, as the concrete mix has to be stronger, and 'should' have rebar in them. the exterior before back-fill, they get tarred/rubberized/eurothaned as moisture protection.

the floor is generally a softer concrete. the last 3-5 years or so, the concrete companies have been putting down a vapor barrier on the ground before pouring the floor. Concrete is porous and with the plastic down; the concrete will not soak up water. No hydro-static pressure leaks through settling cracks and etc.

I wouldn't worry too much about laying plastic, but those subfloor panels are a great idea.

If you are still concerned about water. Have a sump w/sump pump installed.

[LLLimit]

Originally posted by barmanjay

the floor is generally a softer concrete. the last 3-5 years or so, the concrete companies have been putting down a vapor barrier on the ground before pouring the floor. Concrete is porous and with the plastic down; the concrete will not soak up water. No hydro-static pressure leaks through settling cracks and etc.

Several years ago when I was working at a concrete plant in Edmonton. Basement floors were 20mpa w/o air entrainment, poured on a layer of bedding sand. It should be the same here.

Gradebeams, basement walls, footing were also 20mpa but w/ air entrainment.

[Kloubek]

Well Jay, I was going to build a subfloor using wood with plywood on top. Should help it from getting too cold down there. And I was GOING to put a vapor barrier down too - but you don't think that is required eh? Interesting - that would save me a hundred bucks and some time...

[HungryJack]

Originally posted by barmanjay
foundation walls aren't really an issue, as the concrete mix has to be stronger, and 'should' have rebar in them. the exterior before back-fill, they get tarred/rubberized/eurothaned as moisture protection.

the floor is generally a softer concrete. the last 3-5 years or so, the concrete companies have been putting down a vapor barrier on the ground before pouring the floor. Concrete is porous and with the plastic down; the concrete will not soak up water. No hydro-static pressure leaks through settling cracks and etc.

I wouldn't worry too much about laying plastic, but those subfloor panels are a great idea.

If you are still concerned about water. Have a sump w/sump pump installed.

Only certain builders use poly or any other vapour barrier in their basements, Jayman for example does this, whereas Shane, Excel and Beattie do not.

The excpetion would be where someone is having infloor heating installed, and in that case it's a rigid styro insulation used.

So, in my experience, it's the builder that specs whether they want a vapour barrier, and isn't done as a service by the concrete company.

And the material used underneat hthe floor is just usually 20mm gravel, not bedding sand, here.

[blueToy]

Originally posted by HungryJack




And the material used underneat hthe floor is just usually 20mm gravel, not bedding sand, here.

To add to this , it's usually washed rock and very pourous .

[barmanjay]

i thought the cement co did the plastic - still learning something new every day

well jeff,i suggest you ask the foreman of the job and see what they did

there might be some access holes in the floor for future plumbing and clean-outs,etc. pop one off and see if there is plastic

[HungryJack]

Well, generally speaking, what is done will be a plastic ring or box put down and poured around where the cleanouts are/will be, so the likelihood of finding plastic in them is slight.

When the cleanout rings are put down , the plastic is cut around them, generally.

[bwling]

Originally posted by Kloubek
Well Jay, I was going to build a subfloor using wood with plywood on top. Should help it from getting too cold down there. And I was GOING to put a vapor barrier down too - but you don't think that is required eh? Interesting - that would save me a hundred bucks and some time...

Another alternative is to use this product. It might be a little more pricey than the method you mentioned, but it's really easy to work with.

DRIcore Subfloor

[barmanjay]

Originally posted by barmanjay
.......
I wouldn't worry too much about laying plastic, but those subfloor panels are a great idea.

If you are still concerned about water. Have a sump w/sump pump installed.

Originally posted by bwling


Another alternative is to use this product. It might be a little more pricey than the method you mentioned, but it's really easy to work with.

DRIcore Subfloor

[Kloubek]

That Dricore (though a little pricey) seems like pretty good stuff. Would it also be suitable for ceramic tiling, or perhaps an additional plywood layer would be a good idea for such applications?

[barmanjay]

i dont have much experience with dri-core to know if you can tile directly. i would assume not and add at least a 5/8" sheet overtop - my opinion