Tile and joist/foundation support

pete1972

I am in the process of tiling my kitchen and den addition with 16" x 16" slate tiles. Someone has told me that the backerboard, tile and thiset/grout adds extra weight and that I'd need to brace between the floor joists (house is built on a crawlspace) to prevent the new tile and grout floor from potentially cracking.

Is this necessary?

I could understand that rationale if all of the tiles were stacked in one place in the room, but it seems to me the added weight is being spread over the surface area of the entire room and the additional weight per square foot is not that great. The weight a 36" x 36" refrigerator puts on an area of the floor is much more than the tiles, and I don't believe joists are beefed up for those.

I want the floor to last, but don't want to do any unnecessary work under the house if not needed.

Any advice is greatly appreciated.

dougrus

It completely depends on the joist spacing, type, wood species and subfloor thickness. Is it 16" on center for the joists? What is that maximum unsupported span? (This is very important)
They are right in that a lot of houses have floors that are not beefed up enough for natural stone.
Post this information and we can help figure out if it is strong enough.
So, thats:
Joist spacing (how many inches between the middle of each joist) and size (2x8, 2x10, etc.)
Maximum unsupported span (meaning how long do the joists go until they are supported by a beam of some sort) It is listed below as joist length...
Wood species (Douglas Fir, etc)
Subfloor thickness

type it in at the link below, as this will give you a deflection score, and it will tell you if you are good to go for natural stone:
http://www.johnbridge.com/vbulletin/deflecto.pl

If not, sistering joists, etc, may be in order.

__________________
Doug Russell

"What if the hokey pokey really IS what its all about."

pete1972

Thanks Doug. I will get that information and post ASAP.