roof joist repairs

[caseyjones1961]

We are having a new roof(welsh slate) on our house so the whole roof has been taken off, some of the joists were rotten at the chimney breast end so needed replacing/repairing.
The repairs are in full swing but the chippy attending to the joists has shored up the old joists with new timbers(5) which don't run the full length of the old joists....is that normal?
As the whole roof is off with unhindered access, we expected the new timber to run from the eves to the chimney but when we queried it we were told that what has been done is acceptable.
I should add that the house is Grade 2 listed so the timber has to be repaired rather than replaced to comply with the conservation bods.
I'll try to add some pics if I can to show what's been done.

 

[catlad]

Sounds like standard practice.

 

[Harbourwoodwork]

Is the chap repairing the roof a carpenter or a roofer. He may not have the skills in roofing geometry. I would presume the rot is at the top end where the the flashing's gone. If that's the case a full length rafter would be the right thing to do. I am only guessing because I can't see it, but it doesn't sound great. If he's not sure what he's doing he could use an existing rafter as a pattern. While the roof is off this job's a piece of cake.

 

[catlad]

It should not be difficult to replace the rafter as long as you can get the rafter length, but cutting the rotten bit out and sistering a new piece in is ok as long as it extends over a purlin.

 

[tony1851]

cutting the rotten bit out and sistering a new piece in is ok as long as it extends over a purlin.

Correct; as long as the new section passes over a purlin, it will be OK.

 

[theoldun]

In the OPs post, he has quite clearly stated JOISTS, three times, so why are people talking about rafters?
If they are rafters by some chance, how do you know the roof consists of a purlin?
Just curious.
Regards oldun

 

[Harbourwoodwork]

Good point Oldun! I guess we are all cursed with trade chauvinism. Always presuming the client has no grasp of the trade jargon.

 

[catlad]

Grade 2 listed, talking about the roof off and rotten joists/rafters around chimney, it will almost certainly have purlins, but the op is not offering anything so!!!!!!!!!!!!!

 

[chickenlips]

Either way if its joists or rafters both need to be supported at both ends of the new peice. Either over a purlin (if rafter) or over a supporting wall (if ceiling joist)
Although some do fix with a 'scab' timber either side of the damaged timber with it screwed/nailed to the existing timber. Usually though this is to an engineers detail.