Repairing rotten joist ends

[m0t]

I have a small office room on the ground floor and the ends of all the joists have been damaged by wet rot.

I solved the water problem a couple of years ago but now I need to fix the damage to the joists.

Having Google'd there look to be four options - replace the joists, sister them, use plates to bolt a new end in or use the angle brackets.

I think I've ruled out replacing them completely because it seems like a total ballache. Sistering seems like it would be difficult because I would need to cut wider pockets into the wall.

What's the best way out of the other two methods? Have I missed something?

 

[Doggit]

Cutting a wider hole in the wall only takes a bolster and hammer; you then sister the joist using about 1.5m, and 2 or 3 coatch bolts with square washers on the nut side.

 

[John D v2.0]

I'm not in the business, but would it not be simpler to forget about the wall pockets and build a sleeper wall up to the joists underneath? That's what I did where our old kitchen joists were touching an outside wall and the wall plate and joists ends were soaked.

 

[^woody^]

Sisters on Hangers, sounds like a goth rock group, but you may like the sound of it.

 

[Doggit]

A couple of whacks with a club hammer, is a lot easier than building a sleeper wall. I know you've fixed the problem, but use tanalised joists, and wrap them in dmp to play safe for the future.

 

[John D v2.0]

True in my case it was sleeper walls aka a row of bricks already, just they were built touching the outside wall. With a crumbling slate dpc it was worth starting again, especially since I wanted to run pipes where the wall plate was.

 

[m0t]

Cutting a wider hole in the wall only takes a bolster and hammer; you then sister the joist using about 1.5m, and 2 or 3 coatch bolts with square washers on the nut side.

What size bolts do you recommend and what sort of pattern? I'm assuming one at each end and one in the middle but are 3 really enough?

 

[^woody^]

3" oval nails, or screws every 400mm or so.

 

[pilsbury]

I've heard using a "W" pattern is wise

 

[JohnD]

there's a special plate used for roofing and heavy carpentry, like a star washer with teeth either side, that you put between two timbers then a bolt through them.

What's it called?

edit

toothed plate (obv.)

 

[Doggit]

I tend to use no 10 bolts, about 6", but make sure there's enough thread on them. One bolt in the middle, and the other two about 6" from the ends. You can put a dog tooth plate in between the joists as John suggest, but I don't think they are necessary. I tend to set the bolts all in the middle of the joist; but it's just personal preference.

 

[vinn]

OP,
Have a look at sovchem.co.uk/bower beams. Their info and pics will give you a good idea of using plates.
Or go on amazon.co.uk & look at what kind of "Bolt-On" sets they offer.

Either of the above solutions is common best practice in the Remedial building trade. Other methods might risk floor sag or, even worse, floor joist creak.

The "W" pattern referred to above is exactly how all nail schedules or bolt-ons should be fixed.
The toothed timber connector is also, as suggested, also necessary for each bolt in a bolt-on.

 

[m0t]

I think I might go the sistering route, I'm assuming I'd need to jack the joists slightly to get the bowerbeams in and I'm a bit worried about the two concrete block partition walls that are currently sat directly on the floorboards.

I'm planning to lift the floor in the next couple of weeks then take a final decision because I've not seen the ends for myself yet (only advised by the electrician who did my rewire and by the state of the skirting on that wall).

Thanks everyone.

 

[Lower]

I would use the original pockets rather than making the existing ones wide to allow a new joist to sit alongside the old.

On a joist by joist basis i would use a jack or prop to support the joist, cut out the damaged section far enough away from the wall to allow a decent overlap, insert a new piece and sister the new piece on both sides rather than just one.

If you jack up the joist prior to cutting it and only do one at a time you shouldn't affect your block walls.

Using tanalised timber and putting some DPC material in between the joist and the brickwork is a good idea. However, i assume that the old ones lasted for quite a long time before the water problem....

 

[^woody^]

All you do is fix the new joists on the side of the existing ones. No jacking, no cutting, no moving.

If you have not actually seen the problem, then you realy need to before you do anything, as it may not be necessary to do the work you propose.

Any rotten timber remaining should be treated. Bear in mind that if any rot is caused by water, then once the water problem is rectified, the rot will stop. If the timber is still largely sound and not soft, then no work may be necessary