Help!! New Garage Floor Cracked..

Lots of opinions, I only recognize two experts here, that's on the finishing side. I own a concrete pumping company, I see every company's mixes, I see every technique, I see every option due to weather with chemicals, all concrete cracks, you usually can't see it with your eyes, your slab was done within your budget, add steel the price goes way up, fiber is the way to go if your pouring thin, 4" for something you drive on is normal, 6" is better. If you have a problem with the job, you goe back to the source, batch weights and chemicals used if it was cold or hot that morning, recycled water at the plant? That's like adding half a percent........ According to your limited info, the concrete was installed correctly, lots of variables, lots of methods, if you had a concrete company do the work, in the contract it will say in legal jargon, concrete cracks are the nature of the beast, if it was a regular contractor who hired on some finishers, well there's your problem, they call in the order, it's up to them to call out what's appropriate for the day, they nail wood together don't forget..... Good luck

 

You always want to put rebar in concrete...Always. But even with rebar ALL concrete cracks. But if you get cracks with rebar, the slab will not move appart at the cracks. I am in the rebar industry and even post tentioned concrete slabs in parking garages crack and every one knows they will. But the reinforcing will hold the concrete together like a screw holds two pieces of wood together.

Bottom line you have a slab that will not work correctly because of how your contractor executed it. You can not use the radiant floor with the slab cracked and moving separate from each side of the crack. The thickend edge also concerns me. ...you should have at least #4 @16" each way in the slab and some sort of right angle bar turning down into the thickened edge with 2 #5 continuous, top and bottom.

The whole thing seems slapped together to me. Hope you can get some resolve.

 

One shure thing about concrete is that is going to crack. Concrete shrinks as it dries. It looks like you sawed controll joints. I dont think you need them on a 28x36 slab. As long as it don't seperate it will be ok. Clean the floor good, caulk the cracks & sawed joints. After it dries a couple weeks roll 2 coats of high gloss concrete sealer (about $100.00) then put 2 coates of wax. you'll lve it.
Chuck

 

If they waited that long it was probally cracked before the sawed it. The saw cuts are just a controlled crack. They are not expansion joints.
Chuck

 

i think we need some new pics of the floor, been a couple days and things could look different, my last shop, 24 x 24, i had the plastic crack stuff used, after a year that was the only crack and you really had to look to see it.

 

if it is only a few days old how come it isn't covered in plastic sheet? concrete needs at least a week covered .....abused things like overpasses cover the concrete for 30 days

 

Im concerned about the radient heat. If the floor is indeed moving as the OP has stated it could possibly cause a leak. If the floor is moving the earth under it is still settling.

 

I poured alot of concrete and we use to spray a garden hose on the slab after it was hard enough to walk on. Just to keep the concrete at a slow cure. I just had my 40X42 6" slab poured and the next morning I saw cut the slab in grids to create controlled joints. These joints are perfectly straight and look like a pin striped floor. This helps the cracks become controlled at the saw cuts only.
Oh and the guy that said cement isnt concrete until you add water is all wrong. Cement is a powder admix that you mix with sand and rock. These 3 items whether still powder or wet make concrete. When you saw cut concrete when its still green, you only deed to cut the top surface about an inch. When the concret shrinks, it will pull at these areas and not shrink and pull randomly. THATS WHY ITS CALLED A CONTROL JOINT.
Theres another product called Zip strip but in my opinion , it looks like crap when it cracks at these strips.

 

cement comes in bags ---concrete comes in trucks

 

Great thread as I'm considering building a garage structure shortly. I had a 60' foot residential bridge constructed over our creek in '04. Used some leftover pre-stressed girders, and had the county bridge engineer act as overseer. He was there at every stage. They poured a 3" slab (6" total deck thickness) with an ungodly amount of rebar, tied to rebar in the girders. Not one crack anywhere and I've had 17 tons across it. Engineer and material costs were worth every cent.

 

Concrete mix comes in bags. Cement is a powder that is part of the concrete mix whether its in a bag or truck. 5 sack mix is 5 bags of cement per yard , 6 sack is 6 bags of cement per yard etc etc.

 

If they overworked it, the PEX may well have moved up (floated) towards the top. With no rebar or mesh, once you start pumping hot water through that PEX you'll probably start to see cracks in the same pattern the PEX is laid in......

When I built my shop, they poured the footings first, lots of rebar and 36 inches deep where they could, some spots are less but sitting on bedrock. Then I built the shop. A month later, the floor was poured in a controlled environment, with tamped gravel, reflective plastic, mesh, PEX, mesh, then fibermesh mix. 28' by 32', no saw cuts, no cracks after 12 years. Did I get lucky? I bought my luck, found a good concrete guy, checked out his work, got references, and paid the price.

 

Lay down tarpaper and install a nice wooden floor over the whole thing. Forget about the cracks. Forever admire the wood floor as it ages with character (just like us).

 

rip it out, start over.

min 4" thick. use 6x6 W1.4xW1.4 wire mesh within 1" of the top of the slab as a minimum. make sure you put it all over well compacted 3/4" crushed stone. I would do 4-6" of stone as a min. Control joints at about 20 ft on center in each direction sawcut in 1/3 the slab depth make sure you are away from the radiant tubing. Cut the control joints as soon as the slab can support the worker and saw.

Fibermesh helps control shrinkage crack width, does nothing for flexural strength or bridging over full depth cracks.

If you are heating the garage, you want to make a thermal break around the perimeter. Separate spread footing and foundation wall or you will be paying to heat the concrete that will heat the soil around the garage. You will be wasting money for years.

Your slab cracked due to poor subgrade prep, thin slab, lack of steel reinf, overworking during finishing and/or too much water in the origianl mix, lack of moist cure or protection, Some or all of the above happened. Next time, stay home when the slab is being poured and/or have a buddy there thats seen it or done it before.

 

Thanks for everyone's concern. It has been determined that the concrete dried between too much between pours and it also over heated. It cracked when cut.

I am not going to touch the crack for now but will wait and see what happens in 30 days.

The concrete contractor is not getting paid at this point.


Thanks for everyone's concern and help through this.

Mike

 

A floating slab is supposed to float. They are poured on sand to allow the slab to float. On well drained ground, the sand will be dry and won't freeze. Compacted gravel will freeze and heave and requires frost walls and heat in the building. In a well insulated building in Wisconsin, the ground will provide enough heat to keep a building above freezing.

I had a problem with a floating slab because the contractor did nor pour it properly. Code calls for 1 foot deep 18" wide footings with rebar in a monolithic pour with a minimum 4" thick floor. When the floor cracked and started to spread apart, it was easy to tell that the floor wasn't even 2" thick and the footings were only about 6" thick. Wire mesh won't hold anything together. When the contractor refused to admit that he didn't do it right, I sued him. The subpoenaed concrete delivery records proved that less than 1/2 the amount of concrete was delivered than a proper job would have required. The contractor had to pay to have the building lifted off the slab and replaced. That was in 1979 and the new floor was laid with 3/4" rebar in the footings and a 1 foot grid in the floor that I paid extra for. Nothing beyond minor cracking.

Anyone installing in floor heating, I have some advice for you. In my pole building, I didn't put any insulation under the floor because I didn't plan on heating the building to over 50 degrees. Heat will rise out of the ground and insulation will stop that heat. If you want to heat your building to warmer temperatures, you should install insulation. My in floor heat pex tubing is laid in a 12 inch layer of sand under the floor. This avoids problems with inevitable concrete cracking and breaking the tubing and the sand stores heat. The heat only runs if it's very cold (-20) and windy.

I also advise a broom finish on garage floors so they aren't so slippery.

 

There are only two guarentees with concrete..1) its going to crack, 2) once its down nobody is going to steal it.

 

A bit off topic but close enough, for the guys that are going to do there own work. I would not buy concrete, cement, supplies for these itmes from any of the big home center h*** d**** or l***"*

why? The products may be name brands but they are special lower cost mixtures for these stores to keep prices low.

We do enough maintence work at the plant to get the tech reps from the manufacuters of these products to visit our maintence dept. The reps will freely tell use that the products at the home centers are a lower grade. We found that masons cement for brick laying was 25% weaker using retail products then real commercial grade sold directly to large builders.

This also applied to roofing products

just fyi

 

What ???? >>>>.

 

Amen, you get what you pay for, no more no less.

 

If you do end up doing a epoxy finish, check the cure time of your concrete ,the ph balance and do a vapor emmisions test[moisture test] which will give yor a fair idea of what is going on.

 

You realize this thread is like old right?

 

Its life these things happen... It like when you get a pair of new shoes and your really careful with them. Then after a week you dont give a shit anymore.. In a couple months you will have oil and dig marks in it any way. Dont lose sleep over it.

 

This thread is over a year old!

 

I'd make him fix it, why pay for something thats not right from the get go?

 

First of all...stop speculating! Hire a professional mason, someone who does flat work as his main line of business. They may involve engineers and some core samples. If there is no mesh or rebar in your slab you are fucked.
If the pad under the slab was not compacted with a jitterbug that could be a reason for settling and cracking. Fiberglass fibers are added to help minimize cracks, it does not take the place of rebar or wire!
I have been in the home building trades for thirty five plus years. Do not continue to build on this slab until your issues are resolved, DO NOT pay any more money to your contractor. Minor surface cracks in residential slabs are to be expected, if it is an open crack that you can stick a wooden match into.......not good.
The style of slab you have is called a thick edge slab or haunches slab, I have built on many of them without any issues. Remember concrete is strong in compression, without wire in it the slab will fail in tension. Call A pro!!

 

Why old threads should auto-lock.

 

Agreed, but as I will be building a new garage/shop soon, this was an interesting and informative read for me.

 

I think the OP was probably advised to quit posting by his legal counsel. So that might explain why the thread dried up. I wonder what happened in the end?