Water Damage to Ceiling — Condensation or Leak?

paperclap

Thank you both so much for all your input.

Shall I remove the polystyrene and boards in just the affected areas, or is it worth just taking the whole lot down, so the whole thing can breathe synergistically? Whoever had put it up had really gone to town with it, as it's right up at the pitch of the roof too!

Jeepers_Creepers

It shouldn't be there. It's counter-productive (it might feel warmer, but it'll also be damp) and very probably damaging (as you've most likely discovered).

In theory, if the boards were well ventilated at the top and bottom to allow a nice up-draught between it and the tiles, then it would be dry behind there. But that would also make it even more pointless as it wouldn't even insulate :-)

It just doesn't work as a system for making your loft warm and dry.

Without doing it properly - with controlled ventilation and a heat source up there (as if it were another room in the house - adding insulation to the underside of the roof in a loft is a very bad move.

Lofts should be naturally cold and draughty. If it is, it'll also be dry.

paperclap

Thank you again so much.

I'll be sure to remove it all this weekend then! :-)

paperclap

Hi all again,

I've had my Father round today to take a look in the loft space at our damp issues.

He believes they are leaks, and not condensation. His thinking is that rainwater is being pushed up behind the tiles and dripping down (due to lack of / deteriorated roofing felt). We went outside, up the ladder, had a peak under some areas of the bottom row of tiles, and the roofing felt had deteriorated, and definitely no longer sat in the guttering.

I would imagine, given the state of it, it is all original roofing felt (from 1955, when the property was built). Where the current polystyrene insulation and plasterboard is still in place, my Father believes it is effectively "holding up / together" the existing deteriorated roofing felt.

Father's suggestions...

Step 1: Prior to rainfall and wind, place a bag (or similar) underneath the problem areas, and see if any rainfall makes its way in. If yes, you know it's a leak.

Step 2: If it is a leak, as a quick / temporary fix, silicone the gaps between the first three rows of tiles in the problem area(s). If the pooling of water stops on top of the bag in the loft... it's 100% a leak.

Step 3: The hard part. Refelt the entire roof, because ideally, it needs doing, and would stop any ingress of water.

After looking online at some photographs of "condensation vs leaks" sort of thing, it does appear that, at least the first photo (large patch), is a leak. The kitchen photo (subtle black dots), I'm still not sure. At this point, it may be worth noting that these two corners of the house (problem areas) are both south / south-west facing. We live very close to the sea in the South East.

The wet timber however, is west / north-west facing... so, food for thought, I suppose!

Very torn on what to do.

I'm confident that I can refelt the entire roof myself (with the help of a few friends). I'm no roofer by any stretch, but feel confident in that I could do it. Just, don't want to do it now, as really want to start renovating the inside and start living (we moved into this house 6 months ago and have been effectively been living in a building site ever since).

Thoughts, suggestions, advice? Maybe the above provides a new perspective on things?

Thank you all again in advance.

FreeBear

Stripping and reroofing with new felt & battens is an option - You'll need scaffolding, so it is well worth doing other roof line & other high level work at the same time. If you are stripping more than 25% of the roof, building regs will kick in - Up to you if you want to get Building Control to sign off the work.. They may want to see extra loft insulation added to bring it up to a minimum of 270mm (if fibreglass/rockwool).

Before messing around on the roof, follow Father's suggestion of plastic sheeting & silicone sealant. It is unlikely that we will experience much in the way of heavy rain until late in the year, so it might be worth planning the reroof for 2022.

Jeepers_Creepers

laurencewhymark said:

Step 2: If it is a leak, as a quick / temporary fix, silicone the gaps between the first three rows of tiles in the problem area(s). If the pooling of water stops on top of the bag in the loft... it's 100% a leak.

After looking online at some photographs of "condensation vs leaks" sort of thing, it does appear that, at least the first photo (large patch), is a leak. The kitchen photo (subtle black dots), I'm still not sure. At this point, it may be worth noting that these two corners of the house (problem areas) are both south / south-west facing. We live very close to the sea in the South East.

The wet timber however, is west / north-west facing... so, food for thought, I suppose!

All we can do from this side of the screen is speculate as best as possible given the evidence we have to work from.

I agree - the first patch is too well-defined to be condensation formed in the room below - it is almost certainly water from above, from the loft area. And, as you say, the speckled patch is less obvious, but still looks defined enough to be caused by water from above.

So, yes, these patches have, most likely, come from above, in the loft.

Next Q - what's the cause? I don't know. Could it be from driven rain? Yes, of course. Could it be from formed condensation? Yes, of course. For either of these causes, the effect could be the same - the water will likely travel down on the underside of the roof under gravity until it reaches the lowest part in the eaves. There it'll drip, land on the ceiling and soak through. 

Any more evidence of the source? Well, there's the very obvious water stain on that purlin which is around half-way up the roof. Again, what's the source? I dunno - have you removed at least that part of the boarding to try and trace it? I think one thing I can say; if that is from rain, I can't see what siliconing the bottom 3 rows will do to help as this from is waaaay above that level.

Any other evidence? Well, while there's nothing to say that it has been caused by condensation, I think I can confidently say that your loft isn't being ventilated enough, and the main reason is the boarding that's been applied.

That's all I can say with some confidence - you need more ventilation up there. I don't know - I simply cannot say - that it's causing your problem, but you still don't have enough ventilation up there.

So, what would I do? Sort out everything that I know is not correct, and then see what happens.

When you say you reckon you can replace the felt, are you talking about stripping off all the tiles first, or by somehow attaching it from the underside? There is only one correct way...

'Felt', as I understand it, has two purposes. One is as a secondary protection layer to catch anything that might get past the outer covering - such as blown rain or from a missing slate. The other is to act as an anti-suction/lift layer to help prevent the slates moving when, say, a door in the house is opened on a windy day and a pressure blast flies up to the loft, or when certain winds flowing over the roof causes 'suction'. But, a roof should do its job perfectly happily without a felt layer. In fact, even if some rain is getting blown past the slates, it'll likely be a random sprinkling, and will be got rid of by - yup - ventilation. I don't think I've ever heard of so much rain being blown up between slates to cause a damp patch. All these air gaps between the slates is 'good stuff' - it keeps your loft dry. If a few drops of rain gets in, it's not a problem.

Have you removed any of the boarding and insulation between the rafters? At least surely do this on the section where the water stain is showing - you should be able to trace these marks.

paperclap

FreeBear said:

Stripping and reroofing with new felt & battens is an option - You'll need scaffolding, so it is well worth doing other roof line & other high level work at the same time.

Well, we hadn't really anticipated on refelting / reroofing just yet... as we may, in some years from now, add a dormer, etc. Which of course, then, would be the natural time to replace the felt and tiles, etc. But, you can't always plan life, I suppose!

Jeepers_Creepers said:

Any more evidence of the source? Well, there's the very obvious water stain on that purlin which is around half-way up the roof.

Ah, no — siliconing the bottom three rows of tiles was purely for the corners of the house — not the wet purlin!

Jeepers_Creepers said:

When you say you reckon you can replace the felt, are you talking about stripping off all the tiles first, or by somehow attaching it from the underside? There is only one correct way...

I would strip the tiles, remove the battens, replace felt... all externally.

Jeepers_Creepers said:

Have you removed any of the boarding and insulation between the rafters? At least surely do this on the section where the water stain is showing - you should be able to trace these marks. 

I have, partially — more on that (in the videos) below

It saddens me that we do everything "by the book" in that we paid for a HomeBuyer's Report, only for them not to flag this as a major issue (especially as these areas were in sight, as missing insulation and boards are apparent).

Today, I had a bit of a tinker around all the problem areas, both inside and out (wish I had done this in the winter months!). So, I hope these videos will give you some more insight. I've taken videos of all three problem areas (dark circular patch above bedroom, small black spots above kitchen, and wet timbers above living room area) — videos in the loft itself, and then externally.

As the videos are too large in size, I've uploaded them all to this WeTransfer link. Hopefully they all make sense!
https://we.tl/t-97YH3VuyxO

Thank you both again for sticking with me on this. Always lifts the spirits to have others share their thoughts!

Jeepers_Creepers

Well, I've looked at them all... and I'm no better informed.

You still have a shed-load of insulation stuffed where it shouldn't be, a couple of patches of damp on your ceiling which could have been caused by leaks or condensation in the loft - we still don't know, and a large amount of speculation

The gaps between your tiles are not unusual. It would still take pretty extreme weather to blow rain up that roof and inside. And even if that happened, a well ventilated loft would soon evaporate it away - just like rain-soaked paths dry in no time at all when there's a breeze.

Back to basics.

You said: "It is important to note that we've not experienced any more or less water in those areas after heavy rainfall. It seems to be around when condensation would typically form (on, for example, windows) — when the outside temperature is very low / moist (coldest days in the winter months)."

Your survey said: "it was noted that the loft was "poorly ventilated", and that the "polystyrene should be removed".

You went on to wonder why "it was poorly ventilated, (and) why the polystyrene should be removed" and I hope you do now understand the reasons?

If you are having dormers fitted in the med future, then it would make complete sense to recover the whole roof then and ensure it's properly ventilated along the soffits. 

Meanwhile, you know what you should be doing. And it ain't speculating.

Someone else had a similar issue where their walls ran with water from the corner of the ceiling. All caused by a poorly ventilated loft.

You should remove ALL that boarding and polystyrene for two reasons - one is to allow the underside of the tiles and the rafters to be properly ventilated, kept dry, and quite possibly even cure the whole issue, and the other reason is that it was a mistake to have it fitted in the first place. The previous owner did not understand what they were doing. It made sense to them that to insulate the underside would provide a warmer loft which must surely be a good thing, yeah? It isn't. Not when it's being heated by the warm, moist air from the house.

Please rip it all out.

Personally I'd rip off all the loose shreds of felt too as it's serving no purpose. It'll be neater and tidier up there, and you will be better placed to monitor what's going on. It'll also allow the air which is coming through between the tiles to help keep that loft dry.