Tiling over bouncy floor

Millertyme · 09-12-2010, 10:34 AM

I will be removing old tiles and putting down new ones. Right now the tiles are over 3/4 underlayment. The floor is a truss system which spans width of house maybe 16'. There is a little bit of bounce, well if you jump, on the floor above. Will this crack my new tiles? The tiles that are there now arent too bad. A few cracks here and there, but not really where the bounce is. Is cdx a good enough underlayment, which is there now. I thought that this shouldn't be used. When I redo the tiles I was thinking of using that orange netting stuff, not sure what it is called, for the proper substrate and it's low profile.

JazMan · 09-12-2010, 07:47 PM

If you think a bunch of hairline cracks in the grout and a few cracked tiles is OK, then go ahead and tile over a bouncy floor.

If the current cracked tiles are caused by too much deflection, you need to stiffen the floor. Is there an open ceiling below this floor? You say the joists are trusses. Please describe them with measurements. Do you know the brand? Look for markings. What is the spacing of the trusses? Accurately measure the span. You say you have 3/4" underlayment, did you mean to say subfloor, or do you have two layer of plywood? You're correct about not using CDX.

By the orange netting stuff do you mean Ditra? If so, it's the best thing since sliced bread.

But the floor still has to meet minimum standards. Let us know the answers.

Jaz

Millertyme · 09-12-2010, 09:31 PM

I couldn't find a brand name. They are spaced 2' o.c. They are 15" high. 2x4 construction.Only about the first 6 or 7 trusses run 22' with nothing underneath. The rest run 12'. Im not quite sure about the subfloor. From underneath it looks like tongue and groove cdx but I cant really tell with the tile on it. There is only one layer.

Bud Cline · 09-13-2010, 09:32 PM

One layer of subfloor is not enough for trusses spread 24" on center. The spans also are dubious.

The "orange netting stuff" certainly isn't going to make up for the difficiencies in your structure.

Why would anyone want to replace old cracked tiles with new cracked tiles?

Millertyme · 09-13-2010, 10:34 PM

the area that spans the 22' is only about 8' wide. In this area there arent any cracked tiles. There are however some in other various spots in the room. Some are near the exterior walls. I thought that these tiles were cracking because of the improper substrate. The house was built in 1988 and these were the supposedly the original tiles. short of putting a supporting wall under neath, is there anything that could be done to stiffen up this floor a bit. The only reason I say it bounces is because the fishtank I have shakes a bit when people walk by it. maybe this is normal. just exaggerated by the shaking water

Scuba_Dave · 09-13-2010, 10:43 PM

How big is the fish tank...gallons ?

**oh'mike** · 09-13-2010, 11:15 PM

Those open trusses can be stiffened up a lot by 'boxing' them------

Sandwich the trusses with 3/4 " plywood on both sides---making slot cut outs for piping doesn't seem to hurt the installation.---Mike---