Strengthening/cutting out old burnt wood.

[24PoW]

Hi, first post on here. Anytime I search for any DIY info I usually get sent to this forum, so I figured this is a good place to start.
I've recently purchased a nice old 1920's semi detached that's needing a LOT of work done to it. Our 'forever home'. After stripping the wallpaper in one of the bedrooms, I noted a huge chunk of cracked plaster that was going to need attention/removed. I whipped it off yesterday, and underneath i found a roof truss which appears to have sustained significant fire damage. I don't know at what point in the building's history this occurred, but considering it'd been lathe and plastered over, I'm guessing pretty early. I should've taken more photos, but clean lathe was nailed to the burnt timbers, and you can see the roofing boards aren't showing any signs of fire damage. I'm guessing this could've happened anywhere between 70-100 years ago - maybe even while the building was under construction.
So what i'm asking is, what should I do here? Reinforce it and cover it up again? Does the burnt timber need treated? (it's bone dry btw. the whole area is). I've got an idea how I want to progress with it, but i'd be interested in hearing other's opinions.
Cheers.

 

[bernardgreen]

That looks like rot due to damp and not fire damage

 

[Deleted member 174758]

I agree with @bernardgreen - definitely not fire damage (which is almost always black). You have, or had, a leak at that point over a period of time. The replacement boards (sarking boards? Difficult to get the contect here, but I assume you are looking upwards) indicate a more recent repair (lightet, cleaner timber). So what's the roof like on the outside? Any obvious signs of replaced slates or tiles at this point? (Which may be a different colour)

 

[24PoW]

I agree with @bernardgreen - definitely not fire damage (which is almost always black). You have, or had, a leak at that point over a period of time. The replacement boards (sarking boards? Difficult to get the contect here, but I assume you are looking upwards) indicate a more recent repair (lightet, cleaner timber). So what's the roof like on the outside? Any obvious signs of replaced slates or tiles at this point? (Which may be a different colour)

Fairly certain that this is burnt wood. It's pretty much charcoal in places and the charring pattern is identical to burnt timber. That's not to say some rot hasn't set in after the fact. Happy to be corrected though.
On the other side of this is a lead gulley. I've had the roof tiles replaced already, but the slates where all over the place after decades of repairs.

Edit: done a bit of quick research and, yeah, rot can look just like burnt timber.
Ok, what now?

 

[foxhole]

Leaking gully leading to water damage and rotting timbers, someone might have taken a blow lamp too it in the past to speed drying .

 

[Deleted member 174758]

Edit: done a bit of quick research and, yeah, rot can look just like burnt timber.
Ok, what now?

As I said before it looks like there are new boards nailed to the top of the structural timbers. These are called sarking boards. Do, can you see if there are any obvious repairs to the roof outside? I suspect that there might have been a displaced tile or slate or possibly a damaged lead flashing (at the base of a wall or chimney) or maybe even damaged pointing which was letting in water and caused the original sarking boards to rot as well ss damagging the structurals. That would explain the need for replacement sarking boards. Also check the roof outside/any abutting wall/any abutting chimney for signs of repair/replacement. At least then you might have a clue what is going on and whether or not you might need a roofer (in other words whether or not it was a good repair)

After that get a screwdriver and see if you can push that into the timber which looks like it is rotted, and if so how far. The idea is to ascertain how bad the rot is. BTW if it is fire damage it often won't push in that far.

Finally during or after rainfall is the area still wet? Can you see any signs of water (runs, hanging droplets, damo patches, etc) in the area of the rot?

 

[24PoW]

Hi @JobAndKnock , sorry for the slow reply, I was on holiday taking a break from the place.
There's a good chance that a repair had taken place to the slate in that area, as it there had been all over the roof. Cant say specifically now though as the roof has been stripped and tiled. The lead gulley also sits a couple of metres down from the chimney, which has definitely been re-rendered with leadwork replaced. Dunno exactly when that happened - maybe in the last decade. There was some real issues with the chimney breasts below with moisture retention in the brickwork. I'm working to rectify/dry that now.
When we moved in, the gutter that the gulley serviced was seriously overgrown with grass and weeds with the roots travelling right down the downpipe. (the next-door neighbour liked it there because a family of sparrows nested there). I cleaned that thoroughly when the roofers had their scaffolding up.
Having now stripped the adjacent bit of ceiling which reveals roof trusses I noticed that a whole lot of plaster from the lathe and plaster ceiling was in there. That's been left behind after a previous ceiling replacement (50s/60s I reckon) where the old ceiling was taken down and replaced with plasterboard. I had to literally shovel it out. Those trusses were fine thankfully.

 

[Deleted member 174758]

The real question is now, "How soft is the timber?", but it does sound as though a previous owner was aware of the issues and had them fixed, which is very positive

 

[24PoW]

At the worst affected area it's rotted about a third of the way through. I scraped away all the soft/rotted wood and it's now all fairly solid when pressing a screwdriver into it.

 

[Deleted member 174758]

If you have got rid of the punky timber you should treat the affected areas with wood hardener. That will stabilise it. On medium to large timbers you can often get away with losing 1/4 to1/3 of the volume

 

[24PoW]

I appreciate your input on this @JobAndKnock . I've got timber to marry onto these sections - for support/reinforcement and for something to fix plasterboard to. There's been some wobbly bevels chiseled into the trusses for the old lathe to be nailed to.