I am about to cork tile my bathroom but the floor board surface is in
poor condition (curled up edges due to CH drying and also past plumbing
work). Following getting them screwed down properly etc I need to board
out to provide a smooth flat surface to tile on to. The dimensions are
approx 2x2m.

In the past I have used hardboard (on top of chipboard) but I think
plywood might be better in this application.

I have a few questions:

1) What's an appropriate thickness for the board, I want it to be thick
enough to disguise the board imperfections (under constant footfall) but
not so thick to loose too much of the skirting (which I'd rather not
refit) and introduce significant level differences with the landing.

2) I have heard talk of wetting down the boards to get them to shrink a
little following fitting ... does this work / is this necessary, as
plywood has long grain running both ways which might the effect minimal?

3) Are expansion gaps necessary around the edge (again the plywood
should be reasonably dimensionally stable)? If so what is a suitable size?

Any other tips/info would be greatly appreciated.

TIA,

Alex.

AlexW wrote:
1) What's an appropriate thickness for the board, I want it to be thick
enough to disguise the board imperfections (under constant footfall) but
not so thick to loose too much of the skirting (which I'd rather not
refit) and introduce significant level differences with the landing.

3/16", with the outer grain parallel to the existing boards.


2) I have heard talk of wetting down the boards to get them to shrink a
little following fitting ... does this work / is this necessary, as
plywood has long grain running both ways which might the effect minimal?

Don't.


3) Are expansion gaps necessary around the edge (again the plywood
should be reasonably dimensionally stable)? If so what is a suitable size?

Tiny, 1/8" or 3mm. What are you covering the gaps with?


Any other tips/info would be greatly appreciated.

I have wondered about using 1/8" (3mm) cork sheets in 2'x3'
(600mmx900mm) size for a cork floor. Unfortunately, these are about
£3.50 a go. You might need about 10 sheets. It might look nicer than the
"normal" size.

Chris Bacon wrote:
AlexW wrote:

1) What's an appropriate thickness for the board, I want it to be
thick enough to disguise the board imperfections (under constant
footfall) but not so thick to loose too much of the skirting (which
I'd rather not refit) and introduce significant level differences with
the landing.

3/16", with the outer grain parallel to the existing boards.

And just to add to Chris' reply - for a bathroom you should get the
waterproof grade ("WBP"): that's one of the main benefits of using ply
over hardboard in this application.

David

Chris Bacon wrote:
AlexW wrote:

1) What's an appropriate thickness for the board, I want it to be
thick enough to disguise the board imperfections (under constant
footfall) but not so thick to loose too much of the skirting (which
I'd rather not refit) and introduce significant level differences with
the landing.


3/16", with the outer grain parallel to the existing boards.


OK. What's the logic behind 'llel grains then?

2) I have heard talk of wetting down the boards to get them to shrink
a little following fitting ... does this work / is this necessary, as
plywood has long grain runningboth ways which might the effect minimal?


Don't.


OK. Again, what's the logic behind this then?

3) Are expansion gaps necessary around the edge (again the plywood
should be reasonably dimensionally stable)? If so what is a suitable
size?


Tiny, 1/8" or 3mm. What are you covering the gaps with?


The comment was applicable to the ply. My intention was to tile over the
gaps (assuming less than say 5mm) with some flexible filler in the gaps
as the edges will not be subjected to any great load. I did this (small
gap though) in my last house on in two bathrooms and it worked fine
(though these were chipboard floors ... latest house is 100+ years older
and the floors are much less dimensionally stable).


Any other tips/info would be greatly appreciated.


I have wondered about using 1/8" (3mm) cork sheets in 2'x3'
(600mmx900mm) size for a cork floor. Unfortunately, these are about
£3.50 a go. You might need about 10 sheets. It might look nicer than the
"normal" size.

I'll have a think about that one. Cost is not my prime concern (at c.
£40) ... getting the right result is more important.

Cheers

Alex

Lobster wrote:

And just to add to Chris' reply - for a bathroom you should get the
waterproof grade ("WBP"): that's one of the main benefits of using ply
over hardboard in this application.

David

Will do. Being a ply punter ... is this synonymous with "marine" ply?

Cheers.

AlexW wrote:
Chris Bacon wrote:
AlexW wrote:

1) What's an appropriate thickness for the board,

3/16", with the outer grain parallel to the existing boards.

OK. What's the logic behind 'llel grains then?

Look at the thicknesses of each "layer" - there will most likely be 3
"layers", one thick in the middle, two thin facings - the thick layer
goes at 90 degrees to the boards, so is less likely to splinter.

2) I have heard talk of wetting down the boards to get them to shrink
a little following fitting ... does this work / is this necessary, as
plywood has long grain runningboth ways which might the effect minimal?

Don't.

OK. Again, what's the logic behind this then?

It's plywood - the layers are bonded at 90 degrees - if you wet it, then
the timber in each "layer" expands much more across the grain, hardly at
all along it. The facings will crinkle and become unstuck (WBP has been
referred to, which is more resistant) - wetting is no advantage, unlike
for paper, or hardboard.

3) Are expansion gaps necessary around the edge (again the plywood
should be reasonably dimensionally stable)? If so what is a suitable
size?

Tiny, 1/8" or 3mm. What are you covering the gaps with?

The comment was applicable to the ply. My intention was to tile over the
gaps (assuming less than say 5mm) with some flexible filler in the gaps
as the edges will not be subjected to any great load. I did this (small
gap though) in my last house on in two bathrooms and it worked fine
(though these were chipboard floors ... latest house is 100+ years older
and the floors are much less dimensionally stable).

I thought you were referring to the ply, in fact...

Any other tips/info would be greatly appreciated.

I have wondered about using 1/8" (3mm) cork sheets in 2'x3'
(600mmx900mm) size for a cork floor. Unfortunately, these are about
£3.50 a go. You might need about 10 sheets. It might look nicer than
the "normal" size.

I'll have a think about that one. Cost is not my prime concern (at c.
£40) ... getting the right result is more important.

Let us know how it turns out if you use larger sheets.. you can see them
in model shops, rolled up like little carpets...

Chris Bacon wrote:

shnip

Let us know how it turns out if you use larger sheets.. you can see them
in model shops, rolled up like little carpets...

Will do.

One more thing, if I can trouble you further...

I was planning to screw the ply down at intevals at the same width as
and centered to the existing boards across the width of the boards.
Replicating the same intervals along the length seems a bit like
overkill ... what do you think is a reasonable spacing?

TIA,

Alex.

AlexW wrote:
I was planning to screw the ply down at intevals at the same width as
and centered to the existing boards across the width of the boards.
Replicating the same intervals along the length seems a bit like
overkill ... what do you think is a reasonable spacing?

Hmm... I'd probably use 6" centres. It might be necessary to miss some
out, e.g. to avoid pulling the ply sharply down into a hollow, which
would show on the finished surface. If you can use a belt sander, or
even a surform, to rub off any really bad ridges/height differences
between the boards that will help. I hope your electric screwdriver is a
good one!

Chris Bacon wrote:
AlexW wrote:

I was planning to screw the ply down at intevals at the same width as
and centered to the existing boards across the width of the boards.
Replicating the same intervals along the length seems a bit like
overkill ... what do you think is a reasonable spacing?


Hmm... I'd probably use 6" centres. It might be necessary to miss some
out, e.g. to avoid pulling the ply sharply down into a hollow, which
would show on the finished surface. If you can use a belt sander, or
even a surform, to rub off any really bad ridges/height differences
between the boards that will help. I hope your electric screwdriver is a
good one!

Looks like "square" pattern is not overkill then. Belt sander and drill
driver are ready to go (DD should be OK, but its had a bit of stick
though!).

Cheers for the advice,

Alex.

"AlexW" wrote in message
...

One more thing, if I can trouble you further...

I was planning to screw the ply down at intevals at the same width as
and centered to the existing boards across the width of the boards.
Replicating the same intervals along the length seems a bit like
overkill ... what do you think is a reasonable spacing?

I've glued 6mm ply sheets onto waterproof chipboard. Whether this is
suitable for you I don't know.

AlexW wrote:
Chris Bacon wrote:

shnip

Let us know how it turns out if you use larger sheets.. you can see
them in model shops, rolled up like little carpets...


Didn't use larger sheets in the end, as I thought it would only really
look right with a "broken bond" effect (personal taste I guess) and the
area I was tiling was so small that the effect would be lost in it with
such large tiles.

I also thought that getting the profiles in the bathroom (curved front
bath + sink & loo) precise might be a little trickier with the bigger
tile & the broken bond etc.

.... maybe next time though, when I get a larger bathroom.

Ta for the help,

Alex