Finishing Roof into Lath and render Wall

[noj]

Advice please - a job for next lime season will be fixing the very leaky pantile roof on our lean-to utility room. It has a horizontal abutment along its length to a lath and lime rendered wall (no bricks involved in the structure) and I can't find any reference as to how this sort of thing is sealed into the wall. It's all so cemented and painted over at the moment I can't see how it's achieved.

I assume there must be some leadwork going through the render into the little cavity before the internal lath and plaster and fixed on the studs/posts, but don't how this is 'properly' done and how the render over the top is finished. Always helps to know what's needed (and the terms involved) before looking for quotes.

The whole roof is probably going to need to come off since there's a fair amount of decay in battens underneath and all the tiles are bodged on with lime, cement, bitumen etc. Just swapping out the cracked and really porous ones may well not be possible without breaking the surrounding ones.

Thanks

 

[MikeG]

Could you do a sketch section, and I'll have a look and see if I can come up with a detail. A photo or two would help. For instance, there are pantiles, and there are pantiles. Some have a neat little profile, and others a really deep curve, and this could make quite a difference to the junction detail.

 

[MatthewC]

... the very leaky pantile roof on our lean-to utility room... all so cemented and painted over...The whole roof is probably going to need to come off since there's a fair amount of decay in battens underneath and all the tiles are bodged on with lime, cement, bitumen etc...

If that's your own assessment, I would suggest that you bite the bullet rather than mess around. In my limited experience, a roof that the average person thinks looks bad is actually on the point of collapse! I was astonished at how weak the battens in my roof were, when we removed all the slates - no wonder slates were slipping all over the place. We never got close to the percentage expected to be re-used.

 

[noj]

MikeG - thanks, here are a few pics. Externally it doesn't look as bad as many, but leaks a lot through cracked tiles. And shows a big crack in the render above too!

 

[MikeG]

On seeing that I would say unhesitatingly............strip it, entirely, and re-roof. Further, you should strip the render from the wall above, because half of it will come away anyway when you take the tiles off, and it has obvious cracks. The water may be getting in that wall rather than the roof, and the junction between wall and roof will, I forecast, be rotten. I also forecast that there will be no lead involved, just a render fillet.

Once the structure is repaired, you can dress your roofing membrane up that wall to the top prior to re-rendering. When you do re-render that wall, I would advocate counter-battenning it such that you have a 25mm airgap between the render and the underlying frame. A render fillet is the traditional sealing detail, and I'll have a little think about how to suggest doing this without relying on it for watertightness. I can feel a little strip of EPDM coming in handy......

What is that black stuff all over the chimney stack? Whatever it is, I'd have that off too.

 

[Flyfisher]

I tend to agree with MikeG. It's a great shame those tiles have been mortared, presumably in an attempt to fix the leaks or possibly hold them in place where the battens have decayed. I suspect it will damage the pantiles when they are removed. You say the roof is leaking - does this imply there is no form of membrane beneath the tiles? This would be another reason to strip, repair and relay the roof.

 

[Roger H]

Top roof doesn't look spectacular either.

 

[noj]

I agree it'll have to come off and the wall will almost certainly need new lath and render as a result - but I may be able to get 50mm of thermafleece and a breather membrane into the wall at the same time. It'd be nice to have a little more than one layer of render and one layer of plaster between bedrooms and the outside world on at least one small portion of the cottage.

There's no membrane under the pantiles - but also there are 12 glass ones in there making a couple of skylights which I guess I'll have to keep and figure out what happens with the membrane there.

It'd be nice to batten the wall out further as suggested but I doubt I'd get consent to change the wall line - it'd then stick out beyond the weatherboarding on the front and rear walls.

I suppose the way forward is find some period roofing people and get quotes and suggestions before applying for LBC?
The upper roof will get some much needed TLC at the same time.
There's the slight advantage in that the room underneath isn't heated and so technically isn't conditioned space, so I shouldn't have to meet building regs insulation requirements. Once it's watertight I will insulate properly though.

It may make sense to leave the black stuff on the stack - no guarantee that removing it would be fully effective and it could end up looking worse than it does now.

Thanks for your thoughts

 

[88v8]

If you plan on reusing the tiles, be sure to have a good stock of replacements. In my experience, most old pantiles do not match other old pantiles!!

Several days in a local salvage yard sorting through literally thousands of tiles that had allegedly come from one roof, yielded at least a dozen varieties, most of which did not interlock at all well.

Ivor

 

[noj]

Thanks Ivor

I don't think many of the existing will be reusable because there's so much cement holding them together.

I've got mixed feeling over using reclaims which are already well through their lifespan or something like sandtoft arcadia https://www.roofinglines.co.uk/product/sandtoft-arcadia-clay-tile? It may be the opinion of the CO that makes that call though - and possibly will depend on the need to retain the glass ones too

For a complete replacement it seems more 'honest' and practical to use new materials so long as the effect isn't too glaring.

 

[Flyfisher]

Matching pantiles - tell me about it!!

For a completely re-tiled roof I tend to agree with noj about using new tiles (though be careful as there are some pretty horrid looking ones out there), but for our pantile roof repairs we only needed to replace about 20% of them so went along the reclaim route, with all the problems of matching that Ivor mentioned. Even so, we have plenty of tiles that don't interlock very well, but it's only wind-driven rain that can get between them and having a proper membrane means it's not really a problem. At least there's good ventilation!

As for glass pantiles, we had a few of those in one roof and quite a few in the outbuildings. However, I replaced them with standard pantiles because there was no real need for them in the attic or the outbuildings, plus I couldn't figure out how best to 'dress' the new membrane around them. I figured it would need some form of frame arrangement, like a rooflight, but even then the battens would be visible (I suppose I could have limited them to a single row though) and the glass pantiles did not lock well with the other pantiles so it would have been quite draughty. Not such a problem in an attic or outbuilding perhaps but pretty hopeless if there was a habitable room below.

 

[noj]

The glass ones don't serve any great purpose - there's been joists and a chipboard ceiling added under them so they only light a crawlspace. I'd lose them happily but that will depend on getting consent - always the subjective question of changing the character of a listed building.

It'll be an experience finding out if the ceiling and rafters originally required consent, along with the blockwork sealing the inside of a door in there, plus the inner wall being constructed from fibreboard nailed over rubber sheets...

 

[a twig]

If you are going new - I used Koramic rather than Sandtoft as personally I found they interlocked better and were a bit more consistent. Also Koramic seemed to be a bit more widely available in my neck of the woods.

The tiles looked far too bright and new when first installed, but as they've weathered over the last year or so they look fantastic

 

[Flyfisher]

The glass ones don't serve any great purpose - there's been joists and a chipboard ceiling added under them so they only light a crawlspace. I'd lose them happily but that will depend on getting consent - always the subjective question of changing the character of a listed building.

Unless the the glass tiles form a significant feature in some way I'd be very surprised if replacing a small number of them would even crop up in conversation with your CO about consent. It certainly wouldn't change the essential character of the building in my view.

Having said that, we briefly employed a specialist conservation building company for some other works and I had a fascinating conversation with them about 'forensic conservation' projects that have involved 'before' photographs and careful logging of all removed materials so that everything could be replaced in exactly the same place and orientation as the original - a bit like shipping London Bridge to the USA I suppose. So perhaps it could be applied to a roof if it was of outstanding historical significance whereby every tile would have to be replaced in its original position on the roof!! Not the sort of project I'd want to be involved with though - well, not if I was funding it anyway! :lol:

 

[a twig]

A stone mason acquaintance was involved in one of those - they do sound interesting but require a huge amount of effort and patience!

In his case, a chimney and its encompassing wall were completely shot - structurally unsound, timbers completely rotten, holes in the wall where stone had fallen out, the whole thing had to be taken down, footings put in, then rebuilt from ground floor up. All the remaining stones were taken off one by one and carefully numbered and photographed so that it could all be put back exactly as it was (there were some soot stains and markings that were of historical value apparently).

The re-build was nearing completion, however while the project manager was off-site, someone unfortunately dropped the bath stone fireplace, which broke spectacularly. Worse, the evidence was also hurriedly binned.

Project manager returns and is horrified, as he has just arranged for the CO to come and check everything and sign it off as done correctly - in two days time. Mason is prevailed upon to "do what he can". Turns out that in all the photographs taken however, not a single one showed the detailing on the fireplace!

From the small amount of info he has, and his feeling and experience of what would look right, the mason turns out a whole new fireplace, complete with heraldic detailing inspired by some other small surviving bits he found elsewhere in the house. Finishes it off, "weathers" it a bit with some soot etc, and it is installed late the day before the CO's arrival.

Big day dawns - CO is being given the grand tour, closely inspects the wall and signs it off - main comment from the CO? "So pleased that you were able to keep the original fireplace..." :lol: :lol: