Replacing rotten joists...

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Hi all

Have moved into a single story cottage, circa 100 years old. The floor has been replaced since then, probably about 30 plus years ago. However i have removed a remnant chimney which was drawing moisture up from the bare earth under the floorboards and had caused localised rot and woodworm. Ive taken up the floor boards and taken out the offending joists and have the replacements (3) ready to put in.

What i'm wondering is do i do anything to the ends of the joists where they sit on the ledge at the sides of the house and where they lie on the sleeper walls. Currently they are sitting on a half inch thick length of wood and have been set in a blob of cement. The previous joist ends were coated in creosote but this didn't stop the rot and woodworm at the ends. The joists i have are treated Norway spruce ones. Do i just put these in same as the originals, or put thick plastic over the ends or what?

Ventilation under the floors is good, but the soil (solum) is damp this time of the year, particularly where i have disturbed it during the excavation of the chimney breast. The other joists away from this area elsewhere in the house seem fine and the rest of the flooring appears to be in good condition.
 
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Maybe I shouldn't butt in here- you may require a knowledgable forum official- but I would suggest you need a roll of damp proof coarse- sold in 100mm and 200mm widths. A heavy gauge black poly-something. I tacked this to the ends and turned under and over 100mm top and bottom. Also put on sleeper wall.
Since it is thinish you won't disturb the heights.
The woodworm- well---see posts on forum.
I'm now praying.
 
True, you need some kind of dpc to isolate the joists from the damp brickwork.

A piece of slate was often used in old houses, set in mortar, but polythene will do it.

However you need to attack the damp subfloor conditions. Have you put in plenty of air bricks? You might like to consider putting down oversite concrete with a membrane beneath, as you have the floor up. Curing the damp should stop the problems.

Personally I am a great Cuprinol enthusiast, and as you have experienced past damp and worm, I would stand the ends of the new joists in a bucket of Green for 24 hours, and give other surfaces a few flowing coats.
 
Thanks, your posts confirmed what i was thinking, i'll be on the case at the weekend hopefully
 
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I have recently had to replace 6 joists in my kitchen floor. I treated them with some low odour cuprinol wood treatment, then wrapped the ends with 100mm DPC, using gavanised nails to tack the ends. I then set them on slate packings in the pockets in the brickwork. I also made sure that all the joists were firm without any movement by packing slate/brick around the sides and tops. When that was done I used offcuts from the joists to nogging them together.
My kitchen floor is well solid now!
 
Sounds great Sonyman, i'm inspired to get to work this weekend!
Thanks again to all for your advise.
 
Interesting thread :).

So, just to clarify, you have:

sleeper wall > DPM > timber wall plate > Joist. The thing is, how do you secure all this? I mean what is the nail supposed to go into? That's what I don't understand :(.

Do you sit the timber plate wrapped in DPM on a bed of mortar to secure this and then nail through the joists into the wall plate? If so, what about puncturing the DPM? Would this pose a damp threat?
 

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