Carpentry/ floor joist question.

ThisIsWeird

Yes, that amount of work could easily be £ks. I am assuming, based on '£100s', that full joist replacement will not be required, but just ends. And also that the floorboards can be reused.
But, we don't know.
Cat4, remember when I suggested you listen carefully to what the joiner says...?
Do continue to get other quotes and don't be sidelined by how cheap you think this one 'will' be - you haven't received the quote yet!
Were you there when the guy was checking it out? What can you see - do the joists look to be fine other than where they sit in the wall? 

What do you mean by the ceiling being 'polystyrene'? You mean loose suspended poly panels like you get in offices, or glued-on poly tiles on the original plasterboard ceiling? For the latter, you may wish to try some DIY scraping off, and see if the p'board underneath is rescuable, in which case only the 'rotten' end strip might need replacing, and then the whole ceiling reskimmed. If the former - proper suspended panels - there's a fair chance they are fireproof panels. But, they won't exactly look homely

pieroabcd

ThisIsWeird said:

I'd have thought the most likely scenario would be that only the rotted joist ends would need replacing - you say 'one wall' is damp, so presumably only these joist ends would need fixing.

If so, a far smaller job. Lift floor in that area, and ditto ceiling below - in that area - cut off all affected timber + some, treat the rest, sort the water issue, and sister new joist sections to the originals. 

Potentially not a big job at all.

Out of curiosity, when you sister a joist do you keep the original in place or do you replace it? If it remains, what's the purpose of keeping it if it's rotting?
Couldn't it affectly badly (with moisture, potentially mould) the sister joist that is in good condition?

At home I've found a sistered joist, but both look in good condition so I started to wonder "why?".

ThisIsWeird

pieroabcd said:

ThisIsWeird said:

I'd have thought the most likely scenario would be that only the rotted joist ends would need replacing - you say 'one wall' is damp, so presumably only these joist ends would need fixing.

If so, a far smaller job. Lift floor in that area, and ditto ceiling below - in that area - cut off all affected timber + some, treat the rest, sort the water issue, and sister new joist sections to the originals. 

Potentially not a big job at all.

Out of curiosity, when you sister a joist do you keep the original in place or do you replace it? If it remains, what's the purpose of keeping it if it's rotting?
Couldn't it affectly badly (with moisture, potentially mould) the sister joist that is in good condition?

At home I've found a sistered joist, but both look in good condition so I started to wonder "why?".

Oops, I may not have used the correct term there.
What I meant was, the remaining good parts of the joists are retained, don't even need to move (just prop them), and all of the rotten end - and a good 2'+ of good wood - is cut away. All then treated tobesuretobesure, and the joist end replaced by an extension piece, either bolted to the side with the required overlap, or butted to the end with one or two side pieces to overlap-join them (the latter is a good option if the receiving slot for the joist is in line).
I guess 'sistering' really means to 'double-up' the thickness to maintain strength as when removing a section for a hatch or window? I just meant it as an overlap - soz.
Yes, all the rot must be removed. 

Where is your sistered joist? Most likely explanation for it is that it was added to increase strength, perhaps to lessen floor bounce or springiness? Often also added for any other strengthening purpose, such as where stairs meet landings. 

pieroabcd

ThisIsWeird said:

pieroabcd said:

ThisIsWeird said:

I'd have thought the most likely scenario would be that only the rotted joist ends would need replacing - you say 'one wall' is damp, so presumably only these joist ends would need fixing.

If so, a far smaller job. Lift floor in that area, and ditto ceiling below - in that area - cut off all affected timber + some, treat the rest, sort the water issue, and sister new joist sections to the originals. 

Potentially not a big job at all.

Out of curiosity, when you sister a joist do you keep the original in place or do you replace it? If it remains, what's the purpose of keeping it if it's rotting?
Couldn't it affectly badly (with moisture, potentially mould) the sister joist that is in good condition?

At home I've found a sistered joist, but both look in good condition so I started to wonder "why?".

Oops, I may not have used the correct term there.
What I meant was, the remaining good parts of the joists are retained, don't even need to move (just prop them), and all of the rotten end - and a good 2'+ of good wood - is cut away. All then treated tobesuretobesure, and the joist end replaced by an extension piece, either bolted to the side with the required overlap, or butted to the end with one or two side pieces to overlap-join them (the latter is a good option if the receiving slot for the joist is in line).
I guess 'sistering' really means to 'double-up' the thickness to maintain strength as when removing a section for a hatch or window? I just meant it as an overlap - soz.
Yes, all the rot must be removed. 

Where is your sistered joist? Most likely explanation for it is that it was added to increase strength, perhaps to lessen floor bounce or springiness? Often also added for any other strengthening purpose, such as where stairs meet landings. 

Makes sense.
My sistering was added just under the wall dividing the two main bedrooms at the first floor, perpendicular to the wall. If I remember correctly it's the only sistering in that area.