Rotten roof rafter?? Advice please!

[Oldhouseissues]

We have uncovered a rotten rafter whilst repairing old leak damage in our new (old) house. I know the pictures aren’t great but what would people do here? Our joiner says to replace is complicated and just to plasterboard over it. Does this look bad? Is there any repair needed or should we treat with some rot killer and go over with plasterboard?

 

[fernicarry]

Is the rotten rafter something to do with a gable? Looks like its coming in at an angle and its a bigger section that the adjacent rafters. That could mean its got a pretty substantial load on it so I wouldn't be too quick to cover it up and hope for the best.

I have a similarly rotten rafter end due to a pin hole in the valley gutter above it. It had obviously been going on for a very long time and water was running into the wall head saturating the wall and caused several of the the first floor joist ends and the front door lintel to rot out too. All completely unseen until some idiot came along and started picking away at it... (me). You might be advised to check for further damage in the vicinity and the downwards direction.

Replacing it would also be a major operation but nothing seems to be under any duress so I guess there is still enough strength in the whole structure for it to do its job. Your joiner may be following a similar thought process. Or more likely he just doesn't fancy taking on that particular job... You could have a roofer look at it for another opinion. The trick will be getting someone who is interested in doing a sympathetic repair as opposed to stripping the whole lot off and replacing it with modern rubbish for silly money.

In my case, its now dry and I've sprayed it with preservative (opinions vary on whether this is necessary, but given it was soaking wet I feel it best to discourage anything from setting up home). I will probably bridle it (brace it) onto the surrounding timbers for peace of mind once I get back to working on that room.

 

[Oldhouseissues]

Many thanks for taking the time to reply. We’re going to strip back more plaster sections to see if we can see more of the surrounding area. The joys of old houses! I’m glad yours is drying out! Well done on resolving it.

 

[Robola]

I had one that had rotted quite badly behind some foil insulation. Fixed the leak then removed all coverings and let it dry out properly and then sistered the rafter with a new one.

It probably would have been ok but we are in a very exposed location with high winds so I went on the safe side.

 

[a twig]

Would also suggest sistering a new one - easy to do and gives you peace of mind

 

[Oldhouseissues]

Thank you @Robola and @a twig for your replies. Sensible solution! Attaching some additional pics for more perspectives on surrounding area and whether this is wet or dry rot? No visible mycelium or mushrooms but some pink discolouration to old plaster and black mould. We are thinking of cutting a section of this old plaster out to see more of what is behind. Does this area look concerning?

 

[fernicarry]

Where is the rotten rafter in those pictures? Is it running up the diagonal of the "upside-down pyramid" in the corner of the room?

 

[Oldhouseissues]

@fernicarry yes that’s correct it’s exactly there!

 

[fernicarry]

That's the one I have a problem with too, I think its called the valley rafter. I can't really see how to sister it for sufficient length hence my plan to bridle it to the adjacent rafters. You've gone a bit further than me in terms of removing plaster though so you might be able to see it a bit better. Check its condition where it disappears into the wall head because it needs to transfer its load into the masonry and its carrying a lot more than a common rafter.

 

[Stevers]

Dry rot isn't something normally encountered in a roof space. Those cracks in the plaster could well be from the suspect valley rafter settling as it deteriorated.

 

[Oldhouseissues]

That’s interesting - I didn’t know that was its name. It runs between the room pictured and it pops out - from behind crumbling plasterwork in the room behind this one. I will dig around for a picture of where it pops out. I

 

[Oldhouseissues]

This is I believe the same rafter poking out in the room that sits behind the one in first lot of pics

 

[fernicarry]

That looks like a jack rafter judging by the splay on the end. I'm not quite sure how that fits in tbh. Were the first pictures you posted taken in the loft? Your water ingress looks to be higher up on the roof than mine was, but water could still have been tracking down the line of the valley causing problems lower down. I think you should cut away some of the plaster in the box room and examine where the valley rafter lands on the wall head.

You had some roofing work done recently judging by the newer copper nails poking through the sarking. What was that to address?

This is taken from my box room and you can see the valley rafter cutting in right to left. The leak was just about where that slightly darker coloured sarking board is. There was a shower cubicle in this corner so the problem was completely hidden and probably had been going on for years or decades. Its not in brilliant condition it has to be said, but the house is still standing...



On the bedroom side I have a similar crack in the cornice and on the corner bead. If that's the worst its going to settle by then I'm not too concerned but I'll still do something to strengthen it before buttoning it up again.

 

[Oldhouseissues]

Thanks for your reply and astonishing similarity of the position! It looks identical. We will cut more plaster away tomorrow and try and investigate the loft a little better. I’ll report back.