Rotten timber-structural or not?

[Cassie]

Today I took down the plasterboard ceiling in the porch, plus a bit of plaster boxing over a piece of timber above the glazed door panel between the porch and hall. I knew it had to be done because the brickwork in the corner was persistently wet and rot seemed to be spreading from inside the boxing. I was expecting to find maybe a lintel. What I’ve found isn’t good, but may not be a total disaster (). I can’t work out what’s the structural bit and what isn’t. Either way, it looks like some work! I’ve taken pics

 

[Cassie]

I’ve drawn a scheme of f what I think it is from the front

 

[Cassie]

And in profile. The green and blue bits are totally rotten. The yellow bit in the void on the profile drawing looks very sound

 

[Cassie]

On the second photo, you can see the new battens that were for the plasterboard ceiling, not attached to the rotten wood behind.But I think bricks are resting on the rotten timber and the ends are in brick. Any ideas what’s going on?! Thank you!

 

[Feltwell]

It's really hard to tell without being on-site Cassie. Someone has clearly realised the roof was rotten in the past, and has put those new timbers in. The new cross-rail at the front, parallel to your rotten timber, is that going into the brickwork each side? Or have the bodgers just face fixed it to the rotten remains of the timber behind?

Either way. rather than trying to correct a bodge it can be quicker, easier and better to rip all the flat roof out and start again. But without seeing it for myself I couldn't say that with certainty, though I do suspect it will be true.

Was that rotten timber originally structural? Yes, it almost certainly held the roof up. But if someone has made a new independently supported frame behind it then it might not be doing much any more. Still wants sorting out though.

 

[Cassie]

Thanks Feltwell, it’s obviously very difficult to see without being there in person with the benefit of a light and a poking instrument. To be fair, it’s hard enough with those! The flat roof I think is cast concrete?? Looks ok I think, from below. I’ll post a pic in daylight. I don’t think the rotten bit above the door is part of the roof, but it does come a little way into the porch. I just don’t know. I definitely think the timber needs taking out and replacing, but I am not skilled enough, tall enough or know enough to do this safely. The roof structure may be ok, but there’s water ingress in the corners, so needs further investigation. Bloody flat roof! One of my neighbours who is intimately acquainted with the peculiarities of these houses also runs a construction company. He came round today and said he didn’t think the rotten bit was structural, but clear away a bit of mess and I’ll come round tomorrow for another look. Maybe we can figure it out. I think it’s probably goodbye to bathroom sorting for this year

 

[CliffordPope]

It sounds scary - a flat slab of concrete possibly supported by rotten woodwork ! I bet you don't linger long underneath it - just nip through hoping it doesn't decide to crash down at that moment
Unless your builder neighbour is absolutely certain the rotten wood is not supporting it, and is willing to stand under the roof while you pull it out, then I think you have two choices;
1) Pull it all down anyway and rebuild
2) Put up a temporary supporting structure inside (scaffold tower?) and then take out all the rotten wood and see what happens.

 

[Lacan07]

Like Feltwell my first impressions was it looks like someone had already responded to rotting joists with the introduction of new structural timber but its difficult to say for sure without seeing it. But then again why is the brickwork still wet, unless the underlying causes were ignored.

 

[Feltwell]

Let's see the roof - cast concrete would be unusual, but folks do do some mad, daft things to old houses.

Don't step on the roof until you're sure it's properly supported!

 

[Cassie]

Morning all. I am inclined to agree with you. I don’t think I want to touch it and I don’t think anyone should unless it’s supported! I had planned before yesterday to get out on the roof and check all around the moulding outside the parapet for failure letting in water, but I’m not doing that now! What a can of worms

 

[stuart45]

How does it look like it was constructed to you? To me, from the photo, the joists have been put into the wall, with noggins inbetween to hold some roof tiles which must have been used as a base for a concrete slab roof.

 

[Cassie]

I think that’s right Stuart. What I’m not sure of is what’s between the very visible new wood and whatever is holding the roof up behind that. There are definitely bricks on top of the rotten wood, but there’s a good piece of wood behind that. I’ll put some pictures up of the roof from above. The drainage is via a small channel which goes into a hopper/downpipe which I’ve replaced as it was completely blocked with vegetation. This hasn’t solved the damp in that top corner though, so something else is going on!

 

[Cassie]

The drainage channel is on the bottom left in the top pic where it’s most wet and rotten inside. The mossy corner is also damp and rotted inside-something wrong with the fall towards the drain? The last pic is difficult to see, but shows the bricks just visible behind the new wood of the roof supports on top of the very rotten stuff. These bricks correspond with the parapet adjoining the house

 

[Cubist]

Among other things I'm also a movie buff and this latest series of posts Cassie had me recalling one of my favourites. Robert DeNiro made a film called '15 Minutes' in which the hero stops for moment as he's about to shoot a rapidly fleeing suspect. Asked afterwards why he did that the hero replies, "Sometimes you have to go away so that you can come back". The reason I mention it here is that I found myself doing just that having seen something of this latest dilemma you're facing and realising I was taking that famous sharp intake of breath between gritted teeth heard so often from builders examining a new money making opportunity.

My key takeaway from that exchange in the movie was that it is wise to take a moment to reflect rather than making a snap decision. Having reflected, I dont think that your porch is in imminent danger of collapse as the bulk of the roofs weight would seem to be carried on the side walls by the 4x2 joists and noggin framework. Can you confirm that the ends of the lateral joists are firmly embedded in the brickwork?

If I'm right then your situation, albeit still very challenging, is not immediately life threatening. That said I would be wary as the rotten timber you have found would perhaps originally have formed part of the structure for the trasition from the main exterior wall of the house to the porch. As a consequence that connection may be weak and quite possibly that weakness has revealed itself in water leakage from the flat roof.

Another question; in one of the pics of the underside of the roof I think I can see what appear to be tiles, is that right?

 

[Feltwell]

Having seen your new pictures, I agree with Cubist - *if* the ends of the lateral joists are firmly embedded in the brickwork then it should be safe enough, even if it leaks!

I had a not dissimilar situation with the porch here, I'll post some pictures up later. My solution ended up with covering everything in leadwork - not cheap but it's fixed the problem, and it should stay fixed for about 100 years!

 

[Cubist]

As the leak appears to be at the outer corner of the porch roof its probably the product of water pooling there and finding a weak spot in either the waterproofing or the drain that should be carrying it away. From your photos it looks like this has been happening for some time but, while this too needs to be addressed, it does not have a bearing on the main issue.

Can you provide a photo of the exterior where the porch roof meets the wall of the house? I am thinking that the 'good' timber you have found behind the rotten one is a heavy wooden lintel and this is carrying the wall above it. If so, then the task of replacing the rotten woodwaork may be a lot easier.

 

[Cassie]

I live a good movie, but sadly find my eyelids generally too heavy to sustain a while one! Reflection is good, thank you for your thoughts cubist. On one side, the lateral joists are embedded in the wall-how well is difficult to tell. On the other, I’m not sure-i think the ends go into the wall, but what I think are noggins are abutted right up to the wall so I can’t see what the condition is.
They look like clay tiles to me, but again I’m not sure. Feeling a bit useless today!

 

[Cassie]

This is the outside of the worst bit. It’s on the first floor so without getting the big ladder out I can’t get a closer shot. There was a clear issue with the drainage of the flat roof ie. Water was running down the wall due to blocked/inadequate hopper/downpipe-replaced (yes, in plastic for now! I’ll need to have the tender off at some point in that area so went for cheap and cheerful!)

 

[Feltwell]

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.

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.

 

[Cubist]

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.