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Unread 09-21-2012, 10:09 AM   #1
cliff
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Join Date: Sep 2012
Location: Toronto, ON
Posts: 8
Cliff's kitchen project - Subfloor Q's

I might as well start a project log/question page.

The project:
New floors (ceramic 12*24's are ideal), lighting and cabinetry, to replace the original cabinets built in 1968 that were refaced in the late 80s/90s.

Background details:
The main part of the room is 9' 8" * 15' 6 3/4", plus a small hall (~3'*4'), pantry (~24"*30") and front entryway (4'*10') with 4 steps.

The floor joists are a nominal 2"*10", actual 9.25"*1.5"*10'4" span, 16" o/c. I couldn't find any stamps on them from the ceiling I've opened up below, but will be opening more this weekend and will see if I can find the species.
Using douglas fir/SYP the deflecto gives me L/766, for an unknown wood L/586, so even worst case still have a bunch of headroom for ceramic tile.

The sheathing is an actual 4 5/8" * 3/4" and needs to be patched replaced in some spots (see pics) due to some water damage, and in a few other spots cupping of the boards.

Current plan:
12" * 24" ceramic tiles
use schluter's ditra uncoupling membrane
add an underlayment of at least 1/2 (13mm) as called for in Schulter's installation handbook. I'll likely go 5/8


Where I need help:

1) The plank subfloor, the nails are not holding all well anymore after the removal of the previous vinyl tile and ceramic over top of it. There are a bunch of sqeaky spotes If it's reasonable to keep it, while replacing the damaged areas and planing/sanding down the cupped planks, what size screw should I use to reattach them to the joists? (2 or 3 screws per plank?).

2a) Is it even worth saving the plank subfloor?, or would it be less time consuming and give me a better floor if I tore it out and replaced it with 3/4 (7/8?) T&G, (5/8 min OSB or plywood as per the install handbook), screwed and PL premium'ed to the joists, then the ditra. It would be a plus that the overall height would be less and closer to the existing strip hardwood, but still above (the ~1.25" strip hardwood will eventually be replaced in the living/dining room with 3-4" plank at some point, but we are a couple years away from that project).

2b)if the tearout is best, how do I support/join in the new subfloor to the old under the walls in the last two pictures, one directly on the joist, the other ~4" in front of it?

2c) Am I better off with the tearout of the existing subfloor, replacing it with 3/4, and then adding a second layer of 1/2 underlay before the dirta? (or is this overkill for ceramic?)

3) The install manual calls for Exposure 1 plug faced plywood (and from reading on here no face less then C). The Lowes and Home Depot around here (Toronto, Ontario) don't have meaningful grades on their plywood. For example a sheet from Lowes Plywood Sheathing T&G 5/8 on the tag, and stamped Exterior DFP on the sheet. Home Depot had Spruce T&G 3/4 stamped Exterior CSP, no mention of exposure 1, and they did not have the finish of a G1S sheet, (is that high of finish required?), or will the latex pc motar be sufficient to fill the small voids/chips and grooves in the sheets.


Thanks for all the help
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