Rotten Joist

[bobbinboy]

Firstly as this is my first post I would like to say thanks for the all the info on this site, it has been a great help in my new house.

On lifting the floorboards on one of the first floor bedrooms it is apparent that one of the joists is rotten where it goes into the outside wall. Is it possible to repair this without replacing the whole joist?

Can I cut away the end that is rotten and then put a new piece on the end with two sister pieces either side held together with coach bolts? I have read that i need to treat the wood with preserver and nail DPC round the end to stop future rot, so is this right as well?

Thanks.

 

[noseall]

are there healthy joists either side of the rotten one?

 

[Static]

Rotten as in... insect infested, dry rot, wet rot etc??

 

[^woody^]

You can also use steel splice plates.

And consider putting it on a joist hanger and not back into the wall. Much better than wrapping it in polyphene.

 

[bobbinboy]

I think it is dry rot and I don't think it is infested (no woodworm holes but are there other signs?). Also the two joists either side look OK. Can you explain 'steel splice plates'?, I am guessing they are as they sound a plate either side joining the old to the new?

 

[Tozzy]

Why does the joist have to be treated by means of DPM when it is way above ground level? I don't understand.

Can you explain 'steel splice plates'?, I am guessing they are as they sound a plate either side joining the old to the new?

I think they are these (not sure though):

Original Source:

http://images.google.co.uk/images?svnum=10&hl=en&lr=&q=steel+splice+plate

 

[masona]

Why does the joist have to be treated by means of DPM when it is way above ground level? I don't understand.

When the joists goes through the inner wall exposing into the cavity or external wall which need to be treated from damp and rain etc.

 

[JohnD]

Tozzy, I think the think in your picture is a laminated beam (made by fastening several small boards together instead of using a single large and expensive piece of timber).

It looks rather unusual, though. Perhaps it is an American construction?

 

[masona]

Very popular around here, economical and not too heavy

 

[anobium]

Bobbinboy

If it is just the end that is affected by wet rot, all you need to do is buy a section of timber the same thickness and depth as the existing and allow it to lap on to the existing joist by approx 75 cm.
Then bolt it on to the sound section of joist using 4 no ms bolts and double sided bulldog connectors.
The joint will be as strong if not stronger than the existing joists.

 

[bobbinboy]

Thanks for the responses. I think I'll take the last idea of cutting back to the good wood and then bolting on a new piece of the same size. I may also use a joist hanger rather than putting it back into the wall.