New sub floor question : one floorboard left

10 Aug 2007
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United Kingdom
Take a look at my floorboard photo.

My project is to throw away my old creaky bedroom floorboards and replace with a new sub floor ( 18mm marine plywood in 4' x 8' sheets ).

All the 'easy' floorboards are now up apart from the first floorboard shown. This board is below a window frame and it covers the joist hangers. It is set a few inches into the brick wall along its length. And it seems to be supporting ( see photo ) my 1860's lathe and plaster.

I've never replaced a sub-floor before. Is it safe to replace this first floorboard?

My preference is to take this board out and slot plywood sheets into the gap under the skirting. But is it wiser to leave this board alone and fit my plywood sheets butted up against it?
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leave it alone and butt upto it. O and you might want to stick all them wires around your skirts under the floor also!
Reynard - you will find that the structural timbers for that wall are nailed (using great-big cut clasp nails ... Oh, how the Victorians loved using them to hold their house together) straight into this board. Even if you wanted to you wouldn't be able to get it out easily - it is possible but don't bother as you'd be asking for more problems to fix. If you were going to lay a solid wooden floor, which would be seen, you could nibble some of this old board away and then slip the new stuff under the skirting a little. But, as you are going to lay ply, it's not worth doing. Marine ply? ... don't waste your money ... use exterior grade ply (better value/cheaper).
got to agree with symptoms if the need arises then chisel the old board away
and using marine ply will cost a lot.
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Many thanks for the guidance + replies.

I will certainly leave the concealed floorboard alone and "butt up" - if you pardon the expression. I also promise to tidy up my wiring + secure neatly to joist sides etc under the new sub floor before laying it. I've also got some steel "joist protectors" as well to cover any notched wiring. I checked my ply and it is exterior grade not the marine stuff. so I saved a penny there.

The mistake I *have* made is the ply thickness. I ordered 18mm plywood. With hindsight this is way too thin because my floorboards are an inch ( 26mm ) thick. For the butting up to work I'm going to have to make up the 8mm height difference with mineral loaded acoustic sheeting or the like laid over my ply.
You might want to remove that junction box as screwed electrical connections must be accessible.

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