Joists and beams in suspended floor

[Jim_cam]

I'm currently installing celotex between my floor joists as part of a general renovation of the house (Victorian terraced). When I got all the floorboards up, I found that the gap between the beam running parallel with the front of the wall was completely packed with dirt and rubble, which came up to about the level of the joist along some of the length. It was also blocking the airbrick. I cleared it all out, and found that the section of beam in front of the airbrick was quite damp; I've brushed it off and am leaving it for a few days to see if it dries out properly. The house itself is very dry in general; it's just damp where dirt and rubble were covering the wood.

I also found that one end of the beam has partly rotted away, and that the mortar between the bricks and the beam has mostly crumbled because of the wet. The top and sides of the beam are ok, but the underside of the last six inches has pretty much rotted through.

My question is: what do I need to do about all this? My plan is to remove the two joists that rest on that end of the beam (I'm having to replace them anyway, for other reasons), cut off the end of the beam, and use splice plates (eg http://www.joist-repair.co.uk/Images/BM9.jpg) to attach a clean new section, treated against damp. It's going to be very short, so I don't think it will put inappropriate pressure on the splice plates. I'll insert slate or plastic packers under the beam, then attach the replacement joists.

I'm a little uncertain about whether I need to replace the bricks and the mortar as well; elsewhere under the floor, the beams are often just resting on sleeper walls, but this doesn't look like best practice to me. Any advice would be very welcome!

 

[Mr Chibs]

Hard to say without seeing the condition of your installation.

Re-instatement of blocked air bricks will help.
So will sliding DPC under and wood sitting on brick/mortar, to prevent further damp.

First time I've seen splice plates... good idea, but a bit pricey for what is glorified angle iron.

 

[Jim_cam]

Thanks mate -- I'll try and take pictures tomorrow in case anything else catches people's eye, otherwise I'll press on (and add DPC).

 

[ntl142]

Don't have much to add, other than I'm in the same situation as you. Mine started with a damp patch on an interal wall. Pulling up the boards revealed a huge amount of rubble on the bricks that the joists sit on (therefore bridging the DPC/slate), damp joist ends (not rot/mould), and blocked airbricks. My solution was to clean all the rubble/ general rubbish away and open the airbricks up, and hope the ventilation does the rest. I've put a dehumidifier in the room to help the walls dry out too. Where did all that rubble come from!? Anyway, I'll keep an eye on this thread to see what advice you get.

I wanted to slide extra DPC under the joists in a few places but it wouldn't fit - can I use a car jack to raise the joist slightly to slide the new DPC under the end of it?

 

[Jim_cam]

Good luck! Everyone I've spoken to has said that pulling out the rubble is a good idea -- I thought it would be a small job but it's already involved one trip to the dump, with another in the next day or two.

I'm in the process of putting a DPC in as I level off the joists, and hammering in flat bits of slate on top of the bricks where they joists need to be raised a bit. I've got a small bottle jack that I've been using to raise the joists; its minimum height is about 150mm so it's too big to use in some places -- where there's very little space available I've been using a screw jack (Starrett 190A 'little giant') -- cost a fiver, 57mm at its smallest, very handy.

 

[John D v2.0]

I wanted to slide extra DPC under the joists in a few places but it wouldn't fit - can I use a car jack to raise the joist

I've been putting an off cut off timber on a brick and using it like a sea saw! Just make sure you haven't stacked the old boards further along the joist.
Also good to mortar in a new wall plate in areas where the old is in bad condition