SIL’s whole house remodel from hell is coming to a finish – as is their patience and money. They tried to save money on framers and GC’ing themselves. They are now on their third framer, who is a GC himself. He had to redo all the original framing. And the original plan called only for creating a DR under existing porch! So, since I do landscape constuction, and have gotten my feet wet in most other things, I’m on the hook for tile work (to save $$).
Anyway, kitchen has an island, 4′ x8′ finished countertop dimension, which will be tiled. What is the best substrate for tile over the island? Options could include,
1. ply glued and screwed to cabinets
2. MDF glued and screwed
I’m assuming 3/4″ is adequate as a substrate. Then, is Durock (or equivalent) or a mud-bed the next step, OR should the tile be attached directly to the ply/MDF? If there is no cementious substrate, is latex-modified thin-set OK? Or is mastic preferred?
I realize there are multiple questions contained above, so your patience and thoroughness are appreciated. Thank you.
Replies
mdf is out of the question.
Ply is ... acceptable.
tile backer is prefered.
what's the tile ... and what's the overhang?
4x8 is a big #### island .... and I've never run into a 4x8 cabinet .... so I see overhang problems in their money saving future.
aside from the fact a 4x8 sheet of time weighs alot and being top heavy can be prone to tipping over and killing their dog ... there's other smaller problems thet'll crop up along the way.
first ... like I mentioned ... what's the proposed overhang? I'll bet right now it's too deep ... so ... now how's it constructed so it doesn't droop?
and ... that 4x8 of tile .. again .. is gonna weigh alot ... so what's the framing of the floor it's going to be sitting on?
if the room is big enough to fit a 4x8 island .... I'll bet the framing is at it's max .... and that extra weight "may" be a problem down the road if the floor joists are at their max w/o the island. Especially if the flooring is more tile ... as that island could weaken those floor joists to the point where there's too much vibration and flex ...
and the grout joints on the floor start cracking up a coupla months down the road.
make sure the floor can handle it.
make sure the overhang can support itself plus the tile ...
get some tile backerboard in there somehow ....
and use a good modified thinset. Mastic's not good for much aside from a decorative backsplash ...
plus ... for a small area like that ... don't be afraid of epoxy grout.
just follow the directions on mixing .... work fast ... and use hot ... HOT .... HOT! water to sponge up ... and sponge quick ... with a helper .... have the water so hot U can barely grab the sponge ... and it'll clean up just fine.
On an island .... it'll give the extra protection your relatives will appreciate in the long run ... better yet ... make them sponge and burn their hands ...
and ... don't leave any ... not one teeny tiny bit of epoxy grout on the tiles ... as it don't come up after it sets ....
edge treatment ... don't forget about how your going to do the edges ...
but get those overhang details worked out first ....
Jeff
Buck Construction
Artistry in Carpentry
Pgh, PA
Thanks for input Bucky. To alleviate some of your concerns, we're in CA, where the perimeter foundation is near extinct. Floor is 5" of concrete, with #4 rebar 24" O.C. I'm thinking that's adequate!
There is more than one cabinet comprising this island. Finsih dimensions of the multiple cabs are 42" x 95". She said she was thinking of one sheet of ply; overhangs are now 1/2" on three sides and 5.5" on the fourth where the stools will sit. Architect did envision a wood frame/moulding/fascia wrapping the tile. So overhangs increase by 3/4". That still seems out of scale to me. Any recommendations?
I'm thinking a 12" overhang on that one side (8' long) would be beter to store stools underneath. Which raises the support question. Do think three or four 9" x 9" off-the-shelf corbels over 8' would be adequate.?
For the substrate, you said ply is OK. What's better? Billy's rec was 3/4" ply with "thin-setted" 1/4" cementious backer.
Good idea on the attachment. For removal, no glue and screws from underneath
For floors the recommendation is 1 1/4", or 3/4 + 1/2 plywood, plus a backerboard or membrane. It would be safest to go with 3/4" plus 1/2" plywood, but I would be interested in what Buck has to say here because the countertops do not take as much stress as floors (except for the overhangs). The reason for the 1/4" backer is that it is a better surface for tiling, and it acts to decouple the plywood substrate from the tile. Instead of backer you could use a decoupling membrane such as Ditra, which will also give you the waterproofing protection. Many people thinset tile directly to plywood but it isn't recommended.
You will get lots of additional expert advice here:http://johnbridge.com/vbulletin/forumdisplay.php?f=1
Billy
Because the tile will be wrapped with a hardwood fascia, I think I could double up the ply to 2 sheets of 3/4" for deflection strength. Or just get 1 1/4 or 1 1/2" ply. Any recommendations on attaching the hardwood fascia to the edge of plywood. I'm thinking plyurethane or epoxy as a glue with pnuematic finish nails.
As far as a finish for the hardwood, without any advice, I would use penetrating liquid epoxy as a sealer, then 2-3 coats of marine polyurethane. So, any advice?
Screw the architect ... wrap the edges of the counter with tile.
Two layers of ply would be better than one, for two reasons: you can stagger the seams to create a stronger top, and you can get a slightly bigger overhang again cuz of the offset seams. Also it would be easier to work with two layers of 3/4 than one layer of 1"+. And it might be harder to find the thicker ply. Ok, so that's four reasons.
I'm sorry, I thought you wanted it done the right way.
What Buck said...
Go with at least a good 3/4 ply -- no MDF under tile! Then put down 1/4" cement backer, spreading thinset (not mastic) underneath the cement backer with plenty of screws. If there is a lot of overhang on the counter, add another 3/4 inch ply under the overhang, glued and screwed to the top ply. Make sure the top is supported well throughout the center. Flex in the plywood can pop the tile or grout -- and it's not unthinkable that one or two people might climb on top of a 4x8 counter...
It is worth spreading Redguard or other waterproofing on top of the cement backer before you tile.
Billy
Edited 12/22/2004 12:32 am ET by Billy
The archy calls for a wood fascia to wrap the tile. Which is great because that hides a doubled up substrate on the overhang. Thanks for that tip.
What is Redguard or similar? I assume that's to protect the ply from the inevitable moisture penetration.
and remember to mount the top from underneath ...like a regular counter top ...
so if and when ... it can be removed if it ever has to be w/o destroying the cabinet.
I like to run a coupla more cross pieces of lumber across the top/inside of the cab to screw through .... or .. in some cases ... even build a whole new framework inside the cab's to support better and take the weight of the cantilever ...
Jeff
Buck Construction
Artistry in Carpentry
Pgh, PA