Hi.

I recently gutted a now 27' x 10' kitchen (from 2 smaller rooms) and found the floor was varied and off by as much as 1 inch, generally sinking to the center of the house built in 1961.

I leveled the T&G spruce floor with custom made 1 1/2" x 10 feet shims laid every 8 inches (on each joist and another in between) and have filled the 'inter shim gaps' with sand mix cement. Making the shims is the topic of a future posting, but its simple, though tedious (32 10 foot shims, not more than 2 or 3 alike) - with a special fence set-up on powerful radial arm or table saw. Then I used sand mix to fill the gaps as cheaper alternative to much more expensive pani plan or plani patch as the fill required about 12 x 66 lbs bags of mix!

Over this now level floor surface will go a plywood base, heated floor with a coat of self leveling cement followed by thin set and ceramic finish flooring. All this adds up to well over an inch in solid substrate to fully support tiles which wil require some mild slope bridging in most doorways.

Dilemma: I am debating the plywood cover:

- 5/8 inch T&G flooring plywood exterior grade screwed every 6" by 8" and down to joist every 16".

and

- 3/8 inch exterior grade ply with no T&G screwed as above screwed at 6" by 8" by 8".

The trade-offs are stronger and almost seamless structural joints with 5/8" T&G ply (laid on the longer room size to ensure all joint are with T&G or fall on a joist where there is no T&G).

versus

a 1/4".

The trade-offs are stronger and almost seamless structural joints with 5/8" ply) to join all pieces into one.

- @ 5/8" thinner floor elevation rise and no T&G (with 3/8" original sub floor + 5/8" I get a minimum solid substrate of 3/4" self leveling cement for the heated flooring cable... about 1 1/2inch total.

- @ 3/8" plywood over shims/cement fill + 1/8" to as much a 1" I get a minimum solid substrate of ...about 1 1/4inch total.

Bear in mind that in most areas the substrate will be at least 1/8" & 1 3/8" higher as a result of the leveling off, so 1 5/8" T&G overkill or will 3/8" do the job? What I want is to be sure is that I get to 1/360 flex, which is the recommended min. flex for ceramic tile flooring.

Thanks for any tips and or experience with issue.

Best regards,. André

André Desmarais
e-mail: [email protected]

Did you ever consider trying to jack up the house where it settled? If it sank this much it probably will continue unless you jack and build a broader footing. Also, if you must stick with all this shimming I might mention that there is no need for exterior or pressure treated T&G plywood as a sub. When doing jobs like this most all of us use cement board, wonderboard, Ditra or Hardiebacker board.

Hi Ballanger b1

Thanks for the tips.

I considered raising the center beam, but quickly dismissed it:

- this condition has existed at least since we bought the house in '75 and there is no evidence of further settling (cracked walls, etc) since. In fact, I suspect the house was built that way, although depending on what time of year and weather conditions during rough construction, there could have been some settling after the rough and before the walls were finished. We never really noticed much of this as the rooms were much smaller and furnished plus a vintage kitchen with built on cupboards.

- Also, a 5' x 10' foot section at one end of the new large room is straight & level, this section is beyond the main beam and supported separately by another post and then leading to a stariway.

- the house is a two storey cottage with a full foundation finished basement. Lifting the center beam 1'', and enlarging a footing would be impractical and costly and eventually crack every wall joint above and some below (basement ceiling) and only lead to more patching.

I will look into cement board and others you have suggested.

BTW the T&G plywood I am considering is not treated, its either exterior grade (made with waterproof glues) spruce or BCFir - which is slightly harder than spruce ply.

Best regards,. André

André Desmarais
e-mail: [email protected]