Rotten timber-structural or not?

[Cassie]

Like most sagas involving old houses, this one is neither quick nor cheap - the porch here at Feltwell Towers.

Have a read of this old post first - this was the first bit we did to our porch, it was before I stripped the ceiling out inside and discovered "Weetabix" joists. When I did this work I thought the flat roof itself was OK - it probably was, as in the felt covering was OK, but what was underneath it was knackered, as I discovered later!

https://www.periodproperty.co.uk/forum/threads/ohh-no-not-another-damp-question.12804/

The next stage - getting the stonework repaired

https://www.periodproperty.co.uk/forum/threads/restoring-deteriorated-sandstone.16614/

Then I discovered the knackered roof structure. I stripped it all out, put new treated joists in, and made a new deck from 1" marine ply with a rear gutter as before. I was getting a lead worker in - alas Quinn, the superb guy who did the bay window in the first thread, has a series of personal tragedies which meant he couldn't do the job. I had a recommendation for another lead worker and, although not quite as exceptional as Quinn, he did do a good job. I decided to go "belt and braces" and got all the stonework covered in lead as well, as I had a feeling water could be soaking in through that. That was a couple of years ago - I've deliberately not done the ceiling inside yet to make sure all is well, it's been bone dry.

Here's some before and after's - with the roof and stonework totally re-done in lead and all the brickwork repointed in lime, it's in a far better state than it was.

View attachment 9334

View attachment 9335

If you wanted to go "belt & braces", you could rebuild the roof structure with marine ply decking as I have and go down the leadwork route.

If what you've got at the moment appears to be secure, i.e. the joists are indeed bearing into the walls OK, you could do worse for now than just give it another coat of a waterproofing compound, over what's already there - with you having sorted the rainwater goods this could buy you some time, though of course it means you can't reinstate the ceiling inside, or you have to be prepared to trash it when you do come back to do the repair properly.

Wow Feltwell, that lead is really something! I don’t know why it’s hadn’t considered lead, or lack of it to be a possible issue on the porch roof previously. When built, I think these houses were quite high spec, and I guess at least some lead around the drain point of the flat roof, and possibly flashing where the roof met the house would be expected?? No such thing is currently there, and may well be part of the source of the issue. Hmm, I’ve got lead envy now

 

[Cassie]

Typically where a builder uses a joist spanning two or more wall to support either a floor above and/or ceiling below, they would bring the brickwork on the outer wall(s) up to the height of the joist to brace it in position. Alternatively they would sometimes use a noggin, lying on top of the brickwork, to provide that bracing and particularly if they wanted a nailing surface for later use. I think I can see exactly that in some of your pictures.

It may seem a little surprising, given the 'apparent' age of some of the timbers, but I think a lot of that roof is original and not the product of later maintenance or modification. My rationale for this is based on the builders use of tiles rather than say timber planks or sheet boards to form the first outer layer of the roof. I stand to be corrected but I believe that builders of the period would use tiles as a base that would be seam filled with a lime mortar before the application of hot pitch to create a water-proof barrier. In effect therefore your porch, or should that be portico given its size, roof was 'tanked'. In such structures it was also common to include drains made of lead. These would frequently become clogged and some pillock may have decided to 'rod' the drains out to clear a blockage. However, a ir/regular drip of water over many years can also cut through even thick lead pipe. May be an idea to check the full route of run off from the flat roof to all its drain points - you may find the hidden internal leaks at the root of your problems

Returning to your earliest pic of the rotten board inside the porch. I think I can see the heads of 'clout' nails and what may be the remnants of a roofing felt. If my eyes are not deceiving me then I think I understand what has happened to the timber - water leaking from the roof has become trapped behind the felt and produced the heavy decay observed.

I would suggest that you leave the roof interior exposed and wait for some heavy rain to observe if and where rainwater may be getting in.

Once thats known then a solution should fall out fairly quickly.

Thanks Cubist, that’s really interesting- it hadn’t crossed my mind that the roof could be original, I assumed it was just another bodge job! I can’t see any roofing felt inside or out-maybe my poor photography! The boxing in front of the rotten timber above the glazed panel door turned out to be lime plaster on laths. I touched it and it fell off, luckily I wasn’t standing under it because it was pretty hefty! We have had some rain and the bit in the top right above the glazed door got even wetter. I’m convinced it’s a problem around the drain point, dripping in somewhere as this is immediately above/outside that bit. The other corner on the same side (2 external porch walls) is also pretty manky. I can see a crack in the stonework above it, so that could be contributing, but I’m also a bit suspicious of the external moulding- it makes a horizontal ledge against the wall and failure of the render there could well be another leak! The problem is it’s so high up-tower scaffold required to get a really good look

 

[Cubist]

Wow Feltwell, that lead is really something! I don’t know why it’s hadn’t considered lead, or lack of it to be a possible issue on the porch roof previously. When built, I think these houses were quite high spec, and I guess at least some lead around the drain point of the flat roof, and possibly flashing where the roof met the house would be expected?? No such thing is currently there, and may well be part of the source of the issue. Hmm, I’ve got lead envy now

Could be that your porch/portico was lead covered too at some point. It was/still is a frequent target of thieving scrotes!

 

[Cassie]

I suppose it’s possible! They’d have been quite conspicuous up a big ladder though I’ll have a nose around the neighbour’s houses and see what I can find they are getting used to me wandering about I think!

 

[Cassie]

So, although no closer to solving the rotten timber problem, I’ve identified the cause! The drain hole from the roof (yellow in the pic) is about a foot away from the hopper for the downpipe. The red bit is the area of maximum dampness inside. From above there a bit of block that’s been put there to try and divert the water I suppose, but no lead or anything. Plants/moss are growing in the area which won’t be helping either! A quick look up the road shows most of these roofs have been redone at some point, a couple have even been built on! Some peoples have their drainage coming out below the square mouldings but I can’t see a patched up hole inside the porch suggesting that was the case here. On ones I can see that haven’t been redone, there is a lead channel directing the water.

 

[stuart45]

Identifying the cause of the damp is the first step, and often neglected by people.

 

[Cassie]

Thanks Stuart-No point redoing it all if you don’t solve the cause I suppose! The damp from that bit of the porch extends into the adjacent hall and lav too, so definitely needs sorting. There also obviously a problem with the other corners. All wet inside. The worst one has a pool in wet weather on top and some cracked stonework above. The timbers underneath are rotten which probably doesn’t help the sagging/pooling there. Once the possible structural issue above the join between the house and porch is resolved, I’m seriously considering putting the scaffolding back up and stripping the roof back, repairing the stonework and render and maybe getting a skilled professional to advise me on lead work. No point wasting my time plastering if I don’t do a proper job on the root causes! Sigh, no rest for the wicked

 

[a twig]

Just a thought - peering one eyed at the porch photo through half a bottle of red - it’s not fibreglass is it?

 

[Cassie]

Hi Twig, also on the better side of a glass of red No fibreglass that I can see inside or out. I do live by the sea though, so maybe alternative bodging materials are available from left over boat repairs? who knows what I could do with some of that! (I don’t have a boat btw, wish I did! Paddle board is fun but only in very fair weather!)

 

[eezageeza]

" Just a thought - peering one eyed at the porch photo through half a bottle of red - it’s not fibreglass is it? "

That was my first thought seeing the second set of pics. We have a fibreglass roof here, and it does look very siimilar.

 

[eezageeza]

Fibre glass roofs are not bodges - they're blimmin expensive, and last a long time (ours, installed way before our time here, is just starting to show its age after maybe 50 years).

 

[Cassie]

Fibre glass roofs are not bodges - they're blimmin expensive, and last a long time (ours, installed way before our time here, is just starting to show its age after maybe 50 years).

Forgive me eezageeza, as you’ve probably surmised, roofing is very far out of my skill set! I’ve been up and looked at/touched the tiles. Definitely feel like clay and I can’t see any fibres or anything that looks like fibreglass. They are dry though which is something! Builder neighbour got held up yesterday and hasn’t been round yet so I’m waiting to see what he says. I’ve also asked a builder who claims to specialise in conservation work to come and have a look. My experience of contractors so far hasn’t always been positive, but I’ll keep an open mind!

 

[Cassie]

The conservation builder came round just now- seems like a good guy, has done quite a bit of restoration work on these houses, and is doing his own farmhouse up slowly! Didn’t seem too horrified by my brick problems either He said the bottom timber isn’t structural but the timber on top of it is and is completely shot. Wanted to get to the root of the reason why so we had a look at the roof and outside. Various issues. The upshot was, cheap option-replace the rotten structural timber with new and do a temporising fix on the roof while I save up for something proper (lead for example) or bite the bullet and get it done once and right. I can’t afford the latter and I’m not totally convinced a whole new roof is required, although partial replacement seems like a poor solution. However, there’s little more than fresh air holding up the house on that bit and temporising is probably a waste of money and will result in the same issues recurring. Better buy a lottery ticket.