Fixing Plywood prior to Karndean fitting

4 Feb 2006
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United Kingdom
Hi. I have a few questions regarding fixing the under ply for a Karndean floor. I have 9mm exterior ply and a 5kg tub of skimcoat.

I plan to fix the board at 6 inch intervals with 1.5inch ring shank nails. Is this ok?
Should I sink the nails or just hammer the nails flush?
Do I skimcoat just the cracks, nails and any imperfections or the whole surface?
And finally, do I need to prime the surface (with diluted pva?) prior to fitting the Karndean?

Hope someone can help me with my questions. Many thanks.
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What are fixing the ply down to? - if it is floorboards you need to ensure the nails will not hit anything underneath eg. pipes/cables, otherwise you should be ok, though 30mm ring shanks would do.

6in. intervals will be ok - a good thump should take them just below the surface.

If the skim coat is Karndean feather finish I usually go over the whole floor and then you will not need to prime before you lay the tiles.

Hope this helps.
Thanks for the tips flooringman. I'm mid way through the job now and things are going well (no movement and no raised edges, etc). Just one more daft question ... what does nailing at 6 inch centres mean? Does that mean every 6 inches around the circumference plus a few in the middle of the board, or that every nail should be within 6 inches in each direction of another nail (if that makes sense?). That would be an awful lot of nailing!

Cheers :)
the second answer. or in mm - 100mm spacing around the edge with a fixing line 12mm from the edge and at 150mm intervals throughout the entire area of each board. Also leave a 1mm expansion gap between the boards.
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Thanks Matty.

I wasn't aware I needed to leave an expansion gap. I've been told to fill any gaps with Karndean Skimcoat.
yep thats correct, i would skim the whole floor with it tho. Scrap it on as thin as possible and sand any trowel marks out

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