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Unread 09-21-2012, 10:09 AM   #1
cliff
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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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Unread 09-21-2012, 10:59 AM   #2
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Welcome, Cliff.

1. The boards definitely need to be well fastened and yours sound like they need re-fastening. It appears to me they were installed with some sort of staples or tee nails. I'd wanna add one or two screws at each loose place or maybe every attachment.

2. Up to you whether you tear out the existing subflooring. We can't see your construction from here and it's sometimes very labor intensive to remove and replace the subflooring.

If you do elect to remove and replace the subflooring, I'd still want more than a single layer of 3/4" plywood were it mine.

I'd likely repair the existing floor to the extent necessary and add at least 5/8" plywood over it due to the wide spacing of the boards and condition.

3. In y'all's grading system, the word Exterior indicates an exterior glue plywood and you do want that. You don't actually "need" the G1S, but that would be a good choice. It's about the same as our AC plywood down here. You can get by with a Select or even a Sheathing grade as I read your standards.

You do not need a T&G panel, but you'll need to be careful that the square-edge lies over the center of an existing board if you use that style.

My opinion; worth price charged.
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Unread 09-21-2012, 12:48 PM   #3
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I just went thru this with my kitchen. I used 1 1/2" deck screws, and refastened every plank twice at each joist. I then added 5/8" T&G plywood over that. However, my kitchen is Hardwood.
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Unread 10-24-2012, 06:57 PM   #4
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Progress update

Well I can't believe it been nearly a month since I posted, much has happened (but not as quickly as I would have liked, having a job, dog and other commitments have slowed things down) and we're starting to see the finish line.

1) Removed and replaced the questionable looking/cracked portions of the structural plank subfloor. Added addional bracing from below to give a better area to attached for the joints and used PL premium to bond to the bracing and joists.

2) Added just shy of 1000 2" floor screws to the plank subfloor (min of 2 per each attachment point). This elimiated all squeaks that were present and helped stiffen things up considerably.

3) Sanded the high spots/cupped planks to ensure a tight fit once the plywood was down.

4) 5/8 T&G exterior ply over everything, 6" spacing in the field, 4" on the edges (max) avoided the joists with 1.5" screws.

5) Received and read the first half of John's book - highly recommended.

6) The tile arrived yesterday, picked up the ditra and thinset today.
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Unread 10-24-2012, 07:02 PM   #5
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Sounds good if those panels are properly gapped. I can't see inna photos.
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Unread 10-24-2012, 07:32 PM   #6
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Flatness (or lack thereof)

Edit:
Hi CX,

Yes made sure to gap them 1/8 in the field and 3/16 to 1/4 around the outside (yes it's hard to see it at the angles I took the photos and with them being T&G),

And now onto the original post:
... and now for the next set of questions:

Last night after I did the thought pose and placed a couple of tiles on the plywood to check for colour, I noticed a slight rocking in a couple of spots (mostly along the outside walls where the cabinets will be going.) This resulted in some forum searching today saying that the rule of thumb is that the most I should see in 1' is 1/16" and no more then 1/4" rise/fall over a 10' span.

Took out the laser level and the tape measure and discovered its not as flat as I thought. I've got some spots where it rises 5/64" in 2', but with the middle of the floor being well within spec.

A couple of pics of the spreadsheet showing the difference (I took measurements in a grid every 2'). The red/green pictures, tried to get them to show larger but the forum seems to clip them down in size highlight the areas where there is a change larger then 2/16 in 2' (after normalizing the values). I've attached the spreadsheet so you can take a closer look at the numbers.


Now that I'm here, and the tiles (24*12) have arrived, what it the best/recommened way to acheive "flatness"?
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Last edited by cliff; 10-24-2012 at 07:36 PM. Reason: added info to the top, addressing CX's question
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Unread 10-24-2012, 09:23 PM   #7
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Hey Cliff,

At this point, I would prep for SLC. With your floor, its a lot of work but that will make the floor ultra flat. That is if you can spare the height increase
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Unread 10-24-2012, 09:32 PM   #8
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Cliff, I'm not sure I could get any useful info out of your spreadsheet even if I could read the numbers, but I can tell you that for the tiles you intend to use the actual industry standard for flatness is no deviation from intended plane of more than 1/8th" in any 10 feet nor more than 1/16th" in any 2 feet.

Those large (long edge) format tiles want a very flat substrate.

If you're not within those parameters, I think Andrew's recommendation might be your best bet.

How flat are you tiles?

My opinion; worth price charged.
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Unread 10-25-2012, 01:23 PM   #9
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Hi Andrew21 & CX,

I'm looking into the SLC, likely have to go that direction. Around the edges/walls does filling the gap between the plywood and drywall with windows & doors foam and then adding the sill seal above it make sense?

The only product the orange box had was: LevelQuik RS (Rapid set) at $43.99/50lb http://www.custombuildingproducts.co...erlayment.aspx
I don't think the rapid set is the way to go - 10 minutes isn't much open time for flow, since I'll likely need at least a couple of bags of it. The second strike would be that the instructions on the bag also call for a metal or plastic lath to be installed first - although it's not in the online instructions for the product - would be hard to go to a feathers edge with lath underneath, no?

After sleeping on it, the spreadsheet is likely too complicated. But I tried to create a matrix of measurements from a known straight line (the laser line) - still too hard to picture exactly what needs to go up/down. I have more them 1/8" in 10' for sure though.

I picked up an 8' length of 1" square aluminum tube from the orange box (the oak/maple was more $ and would need to be honed to be straight, as they were all visibly not straight) at lunch and will get the tape measure out and figure things out that way. The 4' level I had wasn't long enough to adequately show the differences in height.

I put a level across two of the ceramic tiles before coming to work this morning, I could not detect any variation in height in either direction, but will take a closer look at them this evening. Turns out they are not a true 12*24", but rather a 30*60cm ceramic tile (11.811*23.622").

Tile link: NY.RG.GRY.1224.PL
http://www.olympiatile.com/products/...ollection.html


Thanks for all the help so far, it's been great to bounce idea's off of the pro's here.
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Unread 10-25-2012, 01:36 PM   #10
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I purchased a 12x24 tile that is like yours in regard to size. Really, really wish they would give you the actual size of these tiles instead of this "close but not quite" sizing. 12x24 are much easier to snap in half for use when creating a brick pattern.

OK, rant over:
I would look into the SLC option and see if these might help.
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Unread 10-25-2012, 01:43 PM   #11
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Quote:
12x24 are much easier to snap in half for use when creating a brick pattern
How so, Kyle? Your measuring tape should have lots of little marks on it, some no more that a 1/32" apart. A fella with half-way decent eyes can get down to 1/64" by squinting, if the light was good.
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Unread 10-25-2012, 02:02 PM   #12
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I guess I should have said that my OCD likes true 12x24 tiles instead of these fake 12x24. I understand being able to still snap these others in half evenly but my eye starts to twitch a little.
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Unread 10-25-2012, 02:12 PM   #13
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Beer helps that.
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Unread 10-25-2012, 02:30 PM   #14
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Kyle,
I had to special order this from Home Depot. GIves you 30 minutes to work with:

http://www.custombuildingproducts.co...erlayment.aspx

Don't forget the primer!!!

I found out that after doing my first SLC pour it wasn't that bad. You just need someone else to mix the product while you pour out the batch.

Anyway, after I plugged up the floor, I took up the foam around the edges and left them empty. Hung the drywall over it and there's no problem ever since.
You can get metal lath at home depot for about 7/8 bucks a piece. Forgot the measurements but you would need a few pieces. Oh yeah, might want to buy an automatic staple gun too (like 24 bucks) along with 'stainless steel' staples. Or if you have an air gun, get the stapler and have fun.
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Unread 10-25-2012, 04:01 PM   #15
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Quote:
Originally Posted by Cliff
The second strike would be that the instructions on the bag also call for a metal or plastic lath to be installed first - although it's not in the online instructions for the product - would be hard to go to a feathers edge with lath underneath, no?
Cliff, I think you should read the installation instructions for that SLC again. I doubt they permit feathering to zero over a wood framed floor. That's generally only permitted when pouring over a concrete slab or possibly over a CBU installation, but read carefully about that.

There is generally a minimum thickness requirement along with the requirement for the metal or plastic lath when pouring over wood floors.

My opinion; worth price charged.
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