Best way to sort the ends of these joists.

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2 Feb 2019
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I have 4 joists that had rot in the ends. I have taken out the rotten wood and sprayed the timbers. Question is what the best way to repair the ends?

I think I have two options.

1: try and make a diagonal cut right through the joist, inside the loft, just before it emerges to the outside and make a new end which I can bolt/screw on.
2: try and build up the existing wood with filler/glue/small strips of wood. Let it all set and then shape it in situ.

There is a beam sitting on these but it doesn't support much, nothing in the middle actually, and the end joists, 2 at each end, are sound.

They are 180x100mm so quite chunky and getting in to do a diagonal cut will be tricky but I have made cuts like this before, in tight spaces with a small chainsaw.

There's a lot of wood to make up if I go the filler route, and the voids are obviously random in shape. Not easy to trim or machine up to make neat square edges to fit solid wood pieces back in.

The deepest the rot went in was maybe 150mm


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If access in loft is a bit limited due to the roof line it may be difficult to create a sound joint.

You could consider cutting the ends square and either using angle iron on the four corners screwed into sound wood to joint the pieces, or a hole bored in the ends with a steel bar inserted and set in epoxy.
I would cut them off flush, chisel them back so the joint is within the fascia (and not seen), then either dowel the joint or cut a mortice and tenon (loose tenon?). You might even consider fixing the ends to the board above with a screw in a hole, then plug the hole.
Thanks for all the suggestions.

Got into the loft with the chainsaw today. Not the best fun I've ever had, that's for sure.

I cut the ends off about 250mm in just after where the joist is sitting on a cross beam. I cut them square as access wasn't great.

I'm going to use splice plates to attach the new bits. They are not under any load and each bit is only about 250mm long.

I was very lucky that the worst one with rot, the rot had just reached the cut, so there was a hole right through the bit I took off and clean wood on the other side of the cut!

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