Replacing Sub floor wall plates

8 Aug 2017
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United Kingdom

I have found that most of my sub floor wall plates need replacing due to wood rot, they are all on sleeper walls and are not sitting in any of the main walls. I am not 100% sure what would be the best way forward to replace these. Should I try to replace each wall plate separately one at a time under the joists, by first trying to lift the joists a little where I am replacing one of the wall plates. Or is it best to remove all the joists first and then replace all the wall plates in one go, then fix the joists back to the new wall plates. I suppose I am trying to find the best way to be able to keep the level and height of the floor during the wall plate replacements.

I am kind of of new to doing this type of DIY, and want to make sure I am not going to try a tackle it in the most difficult way.

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Sorry about the late reply @Mat_J , but we had pretty much the same issue. The old slate dpc was saturated and as was the wood. But mostly not rotten in our case. The case was complicated because some of the internal masonry walls were built on the floorboards!
Our existing floor was/is not that level anyway, but I can see why you want to keep it.

What we did was got some DPC 115mm wide and used a brick and length of scrap wood to lever the joists up slightly and shove the DPC under.
The areas that were rotten I just smashed the existing wall plate and sleeper wall out of the way (actually a row of bricks on the ground) then dug out the ground under the old wall and laid the bricks again on some mortar. Then I added mortar on top/DPC and a new wall plate levelled up, then when that was hard I just packed out to the correct joist level and screwed it all up tight.

In other places where the wall plate was not so bad, I just smashed out the sleeper wall but left the wall plate floating. Then I mortared a concrete block paver onto the oversite under each joist near the old wall plate, and then inserted folding wedges and screwed them all up.

I doubt any of that is best practice, and it didn't make the floor any more level than it was before, but it was minimal disruption. Hope it's useful
Similar job in my bungalow - damned woodworm ! - lifted the joists with a car trolley jack under a long piece of 4x2
Trolley Jack is a good one if you have it! I was just on Newton's laws or whoever made the mechanical advantage ones!
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Thanks your replies, I haven't replaced the wall plates yet. But I have a better idea on how to go about it.


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