Hi there. I am working on a 1930’s Edwardian terrace house. Dining room floor was in bad condition, the rear 75% of the floor was heavily damaged by woodworm – I could literally tear the boards up with my bare hands and they disintegrated – and the last 25% of the floor nearest the rear wall/outside was also rotten.
The joists along the back wall all have areas of rot, some have totally fallen away, and all show signs of woodworm – unsure if it’s still active or happened sometime in the last 90 years, either way I’m thinking its probably best to replace them all given the state of the wood.
When I took the floor up, the two worst areas of rot in the joists were the two rear corners – assume due to poor air circulation. Joists were not set into the walls, they were sat on sleeper walls (? apologies if I get terminology wrong – three in total; each spanning the width of the room with one at either end and one across the middle of the room.) The sleeper wall at the back of the house was, in areas, totally buried in dirt that had blown in through the air brick, all but one of the honeycombed holes were blocked up, and one corner seemed to have a large pile of dumped lime.. something? See below, looks like cement or plaster maybe? It was hard but not solid like modern cement (the other side of this corner is the outside toilet, not sure if that’s relevant/it was dumped there when that was build) I’ve cleared all of this out for better air circulation in future.
Looks like a slate DPC along the back wall – I cleared out all the junk from under the floor two days ago and am waiting to see if the area dries out, or if it stays damp and there’s more of a problem than just the cavity being full of soil/crap.
Now for the replacement. Current joists are 2” x 3.5” (around 51mm x 89mm). I cannot find direct replacements of the same dimensions, but was thinking to replace wit c24 47x100 or 47x97, which would only raise the floor up by 8 or 11mm. At 400mm centres, I believe this is good for 2.24m. My room is 3895 long by 3100 across, with the sleeper wall across the middle – so I think these are slightly overspec’d but this is to be my open plan kitchen/diner/family room so high footfall and I want it solid. I believe I shouldn’t put noggins where the centre sleeper wall is for airflow reasons, but was thinking two rows of noggins either side (roughly one meter from the front and rear walls), as below:
The 97mm joists will only allow for 75mm Celotex.. but I don’t want to take the floor any higher than I have to. On top of this will be 18mm chipboard or OSB3, followed by an engineered wood floor glued down.
So what I would really like to know is, am I right? Are the joists I have selected up to the job, or do they need to be chunkier or closer together? There is only one air brick across the rear of the house so I think I need to add another – though eventually the plan is for the rear of the house to come off and an extension be added. Am I missing anything? Thanks in advance for any advice/criticisms!
The joists along the back wall all have areas of rot, some have totally fallen away, and all show signs of woodworm – unsure if it’s still active or happened sometime in the last 90 years, either way I’m thinking its probably best to replace them all given the state of the wood.
When I took the floor up, the two worst areas of rot in the joists were the two rear corners – assume due to poor air circulation. Joists were not set into the walls, they were sat on sleeper walls (? apologies if I get terminology wrong – three in total; each spanning the width of the room with one at either end and one across the middle of the room.) The sleeper wall at the back of the house was, in areas, totally buried in dirt that had blown in through the air brick, all but one of the honeycombed holes were blocked up, and one corner seemed to have a large pile of dumped lime.. something? See below, looks like cement or plaster maybe? It was hard but not solid like modern cement (the other side of this corner is the outside toilet, not sure if that’s relevant/it was dumped there when that was build) I’ve cleared all of this out for better air circulation in future.
Looks like a slate DPC along the back wall – I cleared out all the junk from under the floor two days ago and am waiting to see if the area dries out, or if it stays damp and there’s more of a problem than just the cavity being full of soil/crap.
Now for the replacement. Current joists are 2” x 3.5” (around 51mm x 89mm). I cannot find direct replacements of the same dimensions, but was thinking to replace wit c24 47x100 or 47x97, which would only raise the floor up by 8 or 11mm. At 400mm centres, I believe this is good for 2.24m. My room is 3895 long by 3100 across, with the sleeper wall across the middle – so I think these are slightly overspec’d but this is to be my open plan kitchen/diner/family room so high footfall and I want it solid. I believe I shouldn’t put noggins where the centre sleeper wall is for airflow reasons, but was thinking two rows of noggins either side (roughly one meter from the front and rear walls), as below:
The 97mm joists will only allow for 75mm Celotex.. but I don’t want to take the floor any higher than I have to. On top of this will be 18mm chipboard or OSB3, followed by an engineered wood floor glued down.
So what I would really like to know is, am I right? Are the joists I have selected up to the job, or do they need to be chunkier or closer together? There is only one air brick across the rear of the house so I think I need to add another – though eventually the plan is for the rear of the house to come off and an extension be added. Am I missing anything? Thanks in advance for any advice/criticisms!
