Quick question for you guys - Contractor Talk - Professional Construction and Remodeling Forum

98mustangguy · 03-16-2008, 11:46 AM

Ok with all the requirements all of you always say, like double up subfloors/hardy/thinset under hardy/thinset under tiles i have a question. In my house built circa 1940 i have the t&g subfloor no plywood. I have 2 bathrooms that i am re-doing. One purple and one was a greenish blue got to love the 70's. anyways when i pulled the 12x12 ceramic tiles out of the downstairs bathroom i noticed something. the tile were just placed on the t&g no thinset or glue just dry placed and then grouted. Now they have been in there for i would guess at least 20+ years as i have only owned house for 6 yrs. No cracks in any of the tiles and only 1 or 2 chips in the grout not cracks but just tiny little pieces that are like maybe 1-2mm that have come out over time. Question is how is this possible that it has survived for 20+years with all the deflection calculators and the complete lack of thinset and subfloor build up ect. Now i put in a new floor and built up the subloor and used ditra thinset ect. but now i understand quality and it never hurts to overbuild anything but explain to me how it is even neccessary considering that the floor lasted all these years with nothing at all

Bill_Vincent · 03-16-2008, 12:45 PM

How there was no cracking due to the deflection of taking weight and then the weight releasing as people would walk over it, I have no idea. How it stood up to normal building stresses is easy. It's based on basically the same thing Ditra is, but in the extreme-- it had the ultimate "uncoupling" system-- it wasn't bonded to the structure at all! I don't recommend laying tile dry to ANYONE. LIke I said, I don't know how the grout stood up to live loads over the years, but I wouldn't depend on it to work again, and especially in any and all situations.

Also, although this is the first time I've heard of this on woodframe construction, it's actually somewhat common on grade. It's called "sand cushion" installation. It's laid on a bed of wet sand or stone dust. No too common with grouted tile-- more with pavers, or poured terrazzo.