how to replace/fix damaged joist in bathroom? with pic

[AlF2008]

I'm reposting this in here as its got no replies in the flooring board ( which seemed like the logical place )

Anwyay I'm after some advice folks.

The bath in our bathroom had been leaking for years and has rotted away the floorboards at the end where the leak is. I suspected there could be damage to the joist too and I went under the floor to have a look on saturday and found its not in great shape.

Problem is what to do with it. I'd like to remove it and replace it but it looks like its about 30 feet long and goes through a couple of walls I dont see how this could be done without pulling up all the flooring in bathroom and living room. As it passes through the walls I dont think we can just cut out the bad section and replace it. I'm guessing this must be a fairly common problem so whats the normal method of fixing it?

I was wondering whether using joist hangers and running a new joist next to the existing one would be sufficient?

If its being left in presumably it would need treated with something?

This is a pic:



Also the joist is 5"x2" and I was looking for joist hangers on screwfix and they dont do them for that size, is it an unusual size or something?

I'm probably going to be removing the bath and floor this weekend to get access so any advice would be really appreciated.

 

[Lower]

Has the joist actually started to rot or go soft?

I can see the floorboards are well past their best in the photo but the joist doesn't look so bad.

 

[Symptoms]

Alf - poke the joist with a bradawl or small screwdriver to determine how badly rotted it is - my guess would be you've only got surface damage/staining. Has the woodwork dried-out since you fixed the leak? If the joist only has surface damage I'd be tempted to to treat it chemically then maybe (if you want a belt & braces job but not really necessary of damage is slight) 'sister' another joist alongside. This new structural piece could be glued & screwed to the existing (you'll not get nut & bolt combo 'cos of the wall) or it could be positioned nearby so as to pick-up the floor load. Clearly, you'll need to replace the floorboards. Knock a pocket in the top of that wall to support the new stuff to avoid the joist hanger difficulty

 

[AlF2008]

Many thanks for the replies.

The floor boards are being replaced with thick WBP ply so it can be tiled on.

The joist is quite bad (in my opinion) at the top and it is rotten/soft but it is localised to the area photographed. There is some staining on the other side of the wall but the joist there is sound and hence I was only planning on repairing this section in the bathroom. the other areas will be treated.

I suspect the bath seal had been leaking for years as there was a channel down the wall when the plaster had been washed away!

When you say knock a pocket in the wall, do you mean so it sits on the bricks similar to the existing one? i.e. in the picture I would knock out the bit of brick and mortar next to the existing joist (actually looks like a bit of brick and big wedge of mortar to me!) Presumably the way to do it would be to knock right through the wall so the replacement could sit completely on the bricks. I'll obviously need to reroute the pipes but then as the bathroom is getting ripped out that wont be an issue. Then just screw them together with some heavy 4" screws?

Also the existing joist is 5"x2", is that a standard size?

 

[Symptoms]

Alf - 47mm x 125mm treated (metric equivilant of your 5" x 2" but slightly smaller) is commonly available ... go to a timber merchant to get it not a shed.

Yep, just knock a bit of brick/mortar away to create the pocket (a pocket is a hole in a wall to accept a joist or similar). Care needs to be taken when using pockets in external walls or at ground level because of damp issues.

If you screw the new to the old apply building adhesive in the sandwich - we use polyurethane wood adhesive but Gripfill is OK.

 

[AlF2008]

Thanks for that. I've ordered the bits today from the timber supplier I've been using for other stuff - he recommended C16 treated joist which is 120x45 and I'll have enough left over to make noggins for putting the ply down. i'll get some Gripfill too

 

[maltaron]

As the joists are 5X2 am I right in thinking this is ground floor. In any case 5x2 will only span 6ft so you should have a sleeper wall just out of shot in your pic. It will be simple to cut the pocket as suggested previous and support the other end on the sleeper wall - no glue or scews needed.

 

[AlF2008]

Yup its a bungalow so everything is downstairs

The width of the bathroom is approx 2.15m (7') and there is no dwarf/sleeper wall. Hence I'll need to cut a pocket into both walls and then I'm going to glue and screw it to the original one too.