Floor joists dpm ?

[richardrich79]

Replacing rotted floor on mid victorian ground floor.
Reason for rot was damp plus blocked airways.
My question is the wallplate/board that the joists sit on is totally gone and being replaced.
the small wall it sat upon has slate laid along it a a dpm. I'm thinking I may use black plastic dpm on top of the slate (mainly as I have some to hand), is this a good idea or should I just put things back as they were.
Thanks

 

[theprinceofdarkness]

Using modern plastic DP membrane on top of the old (broken) slate is the way to go!
Frank

 

[richardrich79]

Thanks Frank, I thought it would be but I just needed a nudge.

 

[ree]

Are you talking about a wall plate along a knee wall - or a wall plate that the joist tails sit on at an external wall?

Your explanation of "damp plus blocked airways" doesn't really explain anything. Where did the damp come from? Do you now have sufficient cross ventilation?

If a wall plate is rotted out then the joists that touch that decaying plate will probably be affected by fungal decay.

 

[richardrich79]

The danp problem was caused by a broben slate cill and leaking window, happily all fixed now and the airways and subfloor all sorted.
Intrestingly the 'rot' in some of the old oak joists is very localised around the corroded nails securing the joist to the plate timber.