Rotten floor joists

[ippo123]

Hi Folks,

So in the process of ripping out the upstairs bathroom I thought I check the bathroom below as there had been an ongoing leak.
The end ceiling joists appear to be rotten, the worst is about 250mm along from wall on an approximately 2500mm 2x9 joist.

I've read about those metal beams and sistering joints on the forum but is it possible to just get the entire joist out and replace, i think it's like £20 for a 2x9 3.6m and I only need around 2.5m I estimate. So here's me thinking it'll save time on all the cutting, drilling etc with the other method.

The joists sit within the pocket in the wall though so I'm not entirely sure how to get it out or in more importantly i guess.

In terms of the metal beams I'm not sure how much of the joist sits in the wall so not sure if the amount to cut will meet it's threshold.

Some pictures to help.

Thanks,

 

[Wayners]

Yeah.
Replace or fix another by the side

 

[ree]

OP,
What you definitely dont do is is to fix another joist onto an already rotten joist.
Especially when its hard to tell what kind of rot is present: dry rot or wet rot or perhaps both?
Plus, some of the joisting already appears to have been doubled up?
Neither do you glibly start removing any joist or joists until after careful consideration of how to replace them.
OP, to give you more advice you will need to provide better pics of the whole area under the bathroom and pics from above showing the bathroom itself?
All the insulation in the affected area needs totally stripping away.

 

[ippo123]

OP,
What you definitely dont do is is to fix another joist onto an already rotten joist.
Especially when its hard to tell what kind of rot is present: dry rot or wet rot or perhaps both?
Plus, some of the joisting already appears to have been doubled up?
Neither do you glibly start removing any joist or joists until after careful consideration of how to replace them.
OP, to give you more advice you will need to provide better pics of the whole area under the bathroom and pics from above showing the bathroom itself?
All the insulation in the affected area needs totally stripping away.

I’ve stripped all the plasterboard, tiles and lifted floor boards and for now cut the rotten part of the joist off. Here’s what it looks now.
I was considering sistering two 1.2m strips of wood to the 75cm new piece of joist which replaced the rotten section.

 

[ree]

OP,
Its still confusing - why was the block wall built in that peculiar way?
And why was a wall plate inserted?
The wall plate looks to be badly fungal damaged. If its rotten & soft then the floor could sag a little?
I dont see any dry rot but much wet rot.
How have the new short lengths of joist been connected to the old joists?

 

[ippo123]

OP,
Its still confusing - why was the block wall built in that peculiar way?
And why was a wall plate inserted?
The wall plate looks to be badly fungal damaged. If its rotten & soft then the floor could sag a little?
I dont see any dry rot but much wet rot.
How have the new short lengths of joist been connected to the old joists?

Honestly this was before my time. I know this used to be a garage and then the extension was built on top.

I haven’t connected the new short lengths yet but was going to attach with m10 coach bolts with those timber connectors in between.
So the 75cm new wood going into pocket and lining up in front of old joist and then new 120cm each side sisters.

The problem I have is do I need to secure the sistered joists to the wall itself? Not sure I see a triple joist hangar around though.

 

[catlad]

Seems like the last idiots didn't remove the wall plate before continuing building! you have a big problem now its rotten.

 

[Why Not Indeed]

Does a wall plate actually need to be continuous to work? Ie, could the OP dig out the rotten wall plate in sections and insert replacements?

 

[ree]

OP,
As above, you do indeed have a problem.
If the plate needs to come out - it would be beyond DIY work, I'm afraid.
Maybe post some pics showing the outside?
But, for safety & build quality, professional eyes on site are needed.

I did suspect that the structure had previously been a flat roofed extension but refrained from saying anything because I wasn't sure, & I didn't want to give you the 'orrors. Now you reveal it was a garage conversion.

Post #8, The plate could be removed in sections & replaced with pieced-in cut masonry but its not a realistic proposition unless that wall was fully supported above the plate, & perhaps built up from below the joist pockets.

 

[ippo123]

OP,
As above, you do indeed have a problem.
If the plate needs to come out - it would be beyond DIY work, I'm afraid.
Maybe post some pics showing the outside?
But, for safety & build quality, professional eyes on site are needed.

I did suspect that the structure had previously been a flat roofed extension but refrained from saying anything because I wasn't sure, & I didn't want to give you the 'orrors. Now you reveal it was a garage conversion.

Post #8, The plate could be removed in sections & replaced with pieced-in cut masonry but its not a realistic proposition unless that wall was fully supported above the plate, & perhaps built up from below the joist pockets.

It’s just a rendered wall really from outside.
But if I put in a few acros with strong boys just above the rotten wood, would that not be enough to hold the wall whilst I replace the wood?

 

[cdbe]

Just chop out and replace with masonry in stages, the sections under the joists first - 100mm each time. It's just like taking half a brick out of a wall - if the wall plate was rotten to the point of collapse it would have done so. Make sure what you put in is well bedded down and finishes slightly below the bottom of the joists so you can pack them level. If you have nothing suitable just buy a couple of lightweight blocks from B&Q and you can cut to size with a hand saw or what you have available. Just the one acrow you seem to have will do fine for propping. Cut off the joists at least 300mm past any rot, insert a new section into the existing pocket and splice together with another length of 8x2 extending at least 500mm past the joint. Do a quick search for bolt patterns on here.

Bit messy with those cables running through but you'll just have to notch the tops. Tips for getting the timber out - wood drill waggled about, multi tool, good old fashioned hammer and chisel - I'm sure you'll figure it out.

 

[ippo123]

Just chop out and replace with masonry in stages, the sections under the joists first - 100mm each time. It's just like taking half a brick out of a wall - if the wall plate was rotten to the point of collapse it would have done so. Make sure what you put in is well bedded down and finishes slightly below the bottom of the joists so you can pack them level. If you have nothing suitable just buy a couple of lightweight blocks from B&Q and you can cut to size with a hand saw or what you have available. Just the one acrow you seem to have will do fine for propping. Cut off the joists at least 300mm past any rot, insert a new section into the existing pocket and splice together with another length of 8x2 extending at least 500mm past the joint. Do a quick search for bolt patterns on here.

Bit messy with those cables running through but you'll just have to notch the tops. Tips for getting the timber out - wood drill waggled about, multi tool, good old fashioned hammer and chisel - I'm sure you'll figure it out.

Should the spliced piece be hung on joist hanger next to the new wood in the pocket?

 

[cdbe]

I do them like this, no hangers needed:

M12 bolts from Screwfix in a zigzag pattern, some people use dog tooth washers but I just prefer big penny washers on the outside to pull the timber together.

 

[ippo123]

I do them like this, no hangers needed:

View attachment 343511

M12 bolts from Screwfix in a zigzag pattern, some people use dog tooth washers but I just prefer big penny washers on the outside to pull the timber together.

View attachment 343512

Silly question but rather than cutting an aerated or concrete block to fit in the gaps could I use a paving block? It’s height of 50mm seems to fit gap better otherwise I’ll have to cut the other blocks in half.

 

[cdbe]

I nearly suggested that a bit of paving slab would be a perfect fit!!