control joints residential slabs on grade
control joints residential slabs on grade
(OP)
Do you specify control joints for residential slabs on grade for areas that will be covered by flooring?
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control joints residential slabs on grade
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RE: control joints residential slabs on grade
RE: control joints residential slabs on grade
RE: control joints residential slabs on grade
http://www.nceng.com.au/
"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected" Petroski 1992
RE: control joints residential slabs on grade
Mike McCann
MMC Engineering
RE: control joints residential slabs on grade
I am also assuming you would have more problems with hard tile floors.
RE: control joints residential slabs on grade
If you have control joints, then subsequent floor coverings can be put in place without fear of further "random" cracking. Concrete shrinks for a long time...particularly residential concrete that often has a higher water-cement ratio than commercial concrete and less quality control on its placement, finishing and curing.
RE: control joints residential slabs on grade
http://www.nceng.com.au/
"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected" Petroski 1992
RE: control joints residential slabs on grade
RE: control joints residential slabs on grade
I would be interested to know if the procedures in Oz are different than in the US for tile placement.
RE: control joints residential slabs on grade
Mike McCann
MMC Engineering
RE: control joints residential slabs on grade
RE: control joints residential slabs on grade
http://www.nceng.com.au/
"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected" Petroski 1992
RE: control joints residential slabs on grade
RE: control joints residential slabs on grade
Our standard residential raft slab design allows up to 30m length of unjointed slab with 0.3% reinforcement in a 100mm thick slab.
A commonly used flexible floor tile adhesive claims to be able to cope with 0.9mm wide cracking. That's probably why we rarely see cracked tiles.
RE: control joints residential slabs on grade
I guess that due to gravity and OZ being down under, the cracks tend to stay closed?
Mike McCann
MMC Engineering
RE: control joints residential slabs on grade
How do you handle ceramic tiles on suspended floors? They crack as well, and you can't joint them very often.
RE: control joints residential slabs on grade
First, slabs are not usually jointed. Secondly, they are not usually reinforced enough to prevent cracks or to hold the cracks to reasonable widths. I just personally recommend it and now the contractors are starting to do it more often, mostly because of the cracking problems with tile.
We are currently working on a tile debonding failure in a post-tensioned structure.
If you don't cut in joints, the crack width is larger because of the concentration of shrinkage at the joints. Another problem is that polypropylene fibers are often used in residential slabs, thus increasing the space between cracks but also increasing their widths when they occur.
Joint patterns can be chosen so as to highly reduce the probability of wide cracks occurring under anticipated tile application (kitchens, baths, foyers)....sometimes that results in irregular joint spacing and configuration, but it works.
I recommend using a crack mitigation membrane on top of the slab and under tile. This reduces the shear transfer between the slab and the tile adhesive....probably much in the same manner as your flexible adhesive.
I see no reason that flexible adhesives would not work here as well, other than manufacturers and the Tile Council of America do not recommend them, thus putting the design professional outside a defined standard of care (thus increasing liability) if designed so. The standard is a cementitious thinset adhesive.
One problem that we encounter with flexible adhesives on floor slabs in the US is re-emulsification due to high alkalinity and moisture transmission. Non-latex adhesives would probably be fine.
As for aligning tile with joints, that's rarely done except in long, narrow applications. Though the Tile Council requires the design professional to designate joints and locations, it is not often done. Either the membrane is used or you just don't worry about it and let the tile debond if it so desires.
What are some of the brands of flexible adhesives that you use in Oz? I'll give it a shot on my own house first, to see how it works.
RE: control joints residential slabs on grade
The one that I prefer is made by Laticrete and when used with a latex additive, the thinset is very flexible.
IMO, the premix wall tile adhesives are pretty much all junk.
RE: control joints residential slabs on grade
Sold me on the masonry ability of the Mexicans.
Mike McCann
MMC Engineering
RE: control joints residential slabs on grade
You're confusing me, so in the USA they normally don't joint or they do joint.
Interesting, polypropylene fibres wouldn't be allowed within 100m of my slabs.
The way our system works is that generally for any class of site above A,S you require footing at regular spacing's. This regular restraints position ensure that the cracking minor in nature. For A,S class sites I may consider a joint.
http://www.nceng.com.au/
"A safe structure will be the one whose weakest link is never overloaded by the greatest force to which the structure is subjected" Petroski 1992
RE: control joints residential slabs on grade
This is one of the main brands of tile adhesive used in Australia. Recently changed its brand name from ABA to Ardex. I don't know if it is available in the US, but there would be similar products there. Per capita, Australia is a much bigger consumer of tiles than is the US, mostly because of the climate, but I would think Florida would be similar.
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RE: control joints residential slabs on grade
Hokie- The further south you go in Florida and the closer you are to water, the more tile you see. I am pretty sure its a cultural thin in South Florida with the Latino majority and their Spanish architectural traditions (many more tile roofs, CMU and stucco walls, etc.) Now tile is pretty much standard in wet rooms and in many common areas, with laminate and real wood flooring making in-roads, especially with the improvement of laminate flooring quality and low price of material and installation.
I rarely see control joints in residential construction, sometimes in garages but very rarely in the house. Structural engineers have been pretty well kept out of most residential construction, and if its not required by code its not likely many contractors would do it, or know how and where to do it correctly. It would take coordination with the architect to align the joints with flooring transitions or walls but it could be done. Or you could let the slab crack where it wants during curing and then chase the cracks with a grinder and epoxy them, but NOBODY is doing that.
When I do a forensic investigation and people are having tile problems because of cracks in the slab, I give them the options and also warn them about the lack of guarantees.
I've also seen a lot of tenting and de-bonding failures, but that is its own subject. Had it happen on a rental property of mine. I did 4-5 repairs and then gave up and removed all of the tile (myself), did laminate in one room and did an epoxy coating in the rest. It serves its purpose, which is as little maintenance as possible..
RE: control joints residential slabs on grade
Sorry for the off topic post...
RE: control joints residential slabs on grade
"...unjointed slab with 0.3% reinforcement in a 100mm thick slab..."
This will result in fewer visible cracks, and control of crack growth.
When residential slabs are indeed reinforced in the US (probably less than 1/2 the time), it is not anywhere near 0.3%. More like 0.18%. Maybe.
RE: control joints residential slabs on grade
I agree that more often the issue is workmanship; however, there is a correlation to the amount of volumetric shrinkage of the concrete (lots of water in the mix)and the incidence of debonding.
I will be installing floor tile in our master bath this summer, so I'm going to use adhesive instead of thinset to see how it works. I anticipate it will work just fine...just don't know why it is discouraged by the tile industry in the US.