Floor plates and joists

[chriselevate]

I need to replace 2 joists downstairs where there's been a problem (I've known about it a while) where the floor plates and joists have been built (1940) too close to the external wall. Due to this the damp has transferred to plate and then onto the joist.

I've ripped up the floor boards and taken out the rotten joists and plates.

Could I ask your advice on fixing the problem?

Do I do the followings:
1. Build up the wall where the plates sits using 1:4 ballast mix
2. Sit a strip of DPM on the wall
3. Sit the plate (2x4 treated) on the sheet of DPM and keep 1 inch away from the wall
4. Sit the joist back on the plate (2x4) treated
5. Lay the new floor boards on top - the problem is that they were 120mm x 22mm deep floorboards - I guess I this I can only find 18mm deep wood. Is this going to be case these days? If so.... what do I do to build it up as I've got lots to slot in.

I might add another joist next to the one I've cut the floorboards from so I have somewhere nice and stable to sit the first part of floor board - what do you think to that idea?

Would I need to fix any of the above wood down btw?

Thanks for your help

 

[gregers]

you sound pretty clued up over the reinstall of the joists etc but i tend to fix dpm to wall plate with a few small clout nails and wrap up the side closet to the wall just for added protection,then bed the plate down onto the wall with pug making sure its level etc with whats already there,i would cut slithers of dpm and over say a few runs of boards pack up to correct height of original boards.

 

[Harbourwoodwork]

what was under the wall plate originally? set the wall plate at least 2" off the wall you can always float the joists over, tanalised timber all round as gregers said just bed the wall on mortar ,scew nail the joists into the wall plate,3"galvanised round heads will do the job

 

[chriselevate]

Thanks for that guys, really helpful.

When you say "screw nail" the joists to the wall plates you mean - hi them in diagonally?

The wall plates are say on brick build ledges. I guess when I build up the top of the wall with pug I can then drop my DPC onto the pug, sit the wall plate onto it and level it up with the existing one?

When you say pug - I've got some building sand (plastering sand) and cement will this do? A 4:1 mix is what I was thinking?

Thanks

 

[Harbourwoodwork]

Thanks for that guys, really helpful.

When you say "screw nail" the joists to the wall plates you mean - hi them in diagonally?

The wall plates are say on brick build ledges. I guess when I build up the top of the wall with pug I can then drop my DPC onto the pug, sit the wall plate onto it and level it up with the existing one?

When you say pug - I've got some building sand (plastering sand) and cement will this do? A 4:1 mix is what I was thinking?

Thanks

nail the joists on the angle through the edge of the joist into the wall plate ,building sand would be best for bedding the wall plate on

the pug is trade jargon for mortar

 

[chriselevate]

Cheers,

4:1 mix with the building sand?

 

[gregers]

as said i fix dpc to wall plate but thats just me.
dont use plastering sand it will be to sloppy.

 

[chriselevate]

Ill lip the DPC onto the wall plates and ends of the joist using clout nails as suggested. Can't hurt it can it!

What sand would you use then? Builders sand is too soft to take the weight etc you mean (over time of course). And what mix? 4:1 ok?

Thanks

 

[chriselevate]

Sorry, bad Internet connection it posted twice.

 

[Harbourwoodwork]

Building sand is OK,That's what brickies use ,building sand is the finer one plastering or rendering sand is a bit more coarse.

 

[gregers]

building sand is the correct sand to use,not plastering sand.