Replacing wallplate inside brick wall

[Edwardian]

Hi all,

Looking for a little advice if possible. I've recently bought an old house which needs a spot of work. First order of business is fixing the ground floor damp problems. What's got me stuck/nervous is the wall plate for the joists is actually built in to the brick wall (solid wall construction). This plate is rotten and also shows signs of woodworm so I'd like to replace it with fresh treated timber, along with the joists obviously.

I guess my question is, is it safe to remove the wall plate - I wonder if the flemish bond pattern would support the bricks above if it was removed? Or would I be safer doing it in shorter sections?

I quite like the idea of repairing it like-for-like but I appreciate that something like a new sleeper wall, just inside the external so the joists no longer penetrate the external wall, would have better damp resistance. But then I think to myself, this lasted a hundred years already why bother with a new sleeper wall?

 

[catlad]

I would get a length of 6x3 and use that as a support for your floor joists, packed up with bricks. and spray everything with some fungicide.
use a bit of slate or lead between timber and bricks.

 

[vinn]

OP,
First thing is to de-nail the joists.
Are there air bricks giving through ventilation below the FFL?
Remove the remnant of floorboard.

I can see some masonry in a joist bay - is that the remnants of an old chimney breast hearth?
Is there a knee wall in the middle of the joist span?
Do the repair floor boards actually land on the second joist?

 

[Edwardian]

Thanks for the replies and advice.

All the boards are now up, new photo attached - haven't got round to de-nailing yet (sorry Vinn!). The short joists closest to the camera are not original - the originals were evidently cut off and new wood sistered on. In terms of through-ventilation - no, not really. There are air bricks to the left of this shot (one in each alcove) and two to the front (just visible in this image) but the floor I'm standing on is solid/concrete with quarry tiles and there is no ventilation through it at all. From the outside it looks like the front airbricks were added at some later stage (pointing doesn't match the rest of the brickwork) but the ground level was too high and there were weeds obsctructing them too. I've only resolved these issues recently so jury's out on whether this will be sufficient ventilation now?

The joists are old size 4x2 so replacing everything with new treated, regularised timber would leave the floor 10-15mm lower which is a pain for doors/junction with the hallway/etc. If nobody tells me I'm an idiot, I'm thinking of using 45x120mm joists and notching 15mm out where they would mate with the wall plates so as to sit them at the required height. Still not sure what to do about the wall plate inside that external wall though?

 

[vinn]

Will you post a pic of the solid floor that you are standing on - showing how the joist tails meet it?


Why, if I understand you, do you intend to replace all the joists "closest to the camera" - or do you mean that all the joists in the room will be lifted?

Whats going to happen to the hearth - will it be boarded over again?
The knee wall plates dont have a DPC.

 

[Edwardian]

Hi Vinn,

There's a thick wooden threshold which divides the quarry tiles from the floorboards, the joists are notched 20mm or so and slip under it a few inches. They're nailed to the wall plate beneath.

All the wall plates have a DPC beneath them, it's hard to see in these photos but there is a brittle, black bitumen-like substance between all wood-brick junctions. With the exception of that solid sleeper wall, that is, which surprised me because the wall plate there is in the best condition of the bunch. Looking at the photo now I wonder if this wall has a DPC two courses lower? I'll have to confirm that tomorrow.

I intend to replace all the joists, not just those closest to the camera.

Not sure about the hearth just yet, ultimately we'd like to reinstate the fireplace but I might just board it for now in such a way that the board sections can be easily removed for a proper hearth to go back in at some point.

 

[tomfe]

Bolt a new wall plate to the wall with a DPM behind it. Cut out sections of the original and replace with brick.

Or cut out sections of the original wall plate replace with bricks, remove the rest of the wall plate and sit your new joists on the brick work, there is no need for a wall plate.

Or depending on your other floors, substrate etc put in a solid floor with insulation and , if you are in a posh area, underfloor heating.

 

[vinn]

I still dont understand why you are intending to replace all the joists?

The new pic shows the bitumen under the plates.

Cutting off the joists tails that rested in the wall pockets, and removing any other rotted joists is simple enough - likewise, safely removing the embedded plate.

If you board over the hearth you will need a "joist"/nailer against the chimney breast to catch the ends of the boards.

FWIW: remove all cellulose (wood) debris & rubble from the oversite while its open - and pull all redundant cables and pipes.

Lag & clip any remaining cables or pipes.

 

[Edwardian]

So sorry for not following up with a conclusion to this. As you can see, in the end I decided to replace the wall plate with concrete lintel - figured it would make it easier for a rookie like me to get a flat and level surface for the new joists compared to a row of bricks, plus helps spread the load over the bricks beneath in the same way the original wall plate would have. Seemed to work a treat, if I say so myself.

Joist ends are wrapped in DPM, all the timber was pre-treated and cut ends were given extra fungal and insect treatment too.

Also, not pictured, I added noggins between the joists at each end, removed the old (unused) gas pipe and ran and clipped new 2.5mm T&E and CAT6A cable throughout. Treated the original boards, replaced rotten sections with new (treated) timber and finally screwed all the boards down for easy access in future and to prevent any squeeks.

I didn't insulate yet because I've now got to do the same treatment quite urgently to the rest of the ground floor but it's on my to-do list.

Thanks Catlad, Vinn and Tomfe for your time and advice. This floor feels solid as a rock now.