Few damp patches in attic

[AndrewB]

Evening all,

As some may have seen in my other posts I have been removing fibreglass from my 1888 house and replacing with rockwool. Lifted the fibreglass about two weeks ago and have been laying the rockwool bit by bit.

I have noticed a few patches like this. This being the worst one.



There are 4 or 5 similar patches. Dont feel particularly wet, but damp to the touch. All about that distance from the edge. It was raining light and persistent today.

Don't see any obvious tile slippage or anything, but will take a look in he daylight tomorrow.

Assuming this is finding a way in through the slates... How big a concern is it? If I lay my rockwool over the top and get a few drips that dry out... Might thay be ok? I guess it's been dripping onto fibreglass for years.

If not, is this generally something fixed from the outside? I have solar panels coming in a few weeks, so will have scaffolding up anyway.

Thanks for any advice.
-Andrew

 

[AndrewB]

Had a look outside. Nothing here give us any convern, right?





I'm thinking it could be condensation. Would it make sense that condensation would be about 1ft in from the edge? Thought it would normally be at the top.



I think the roof is generally on good shape... So not sure how to explain these patches!

 

[stuart45]

Best time to look is when it's hammering down. Condensation is usually more evenly spread along the underside of the felt or slates. You need to sort it before the panels go on.

 

[Stevers]

The problem with slates is capillary action drawing water up towards the top of the slate where it doesn't dry out easily. On my roof this has caused the slates to rot like a fish from the head down. Definitely take a close look when it's been raining for an extended period, and not it's impossible that it's associated with a fairly specific wind force and direction. In Scotland that roof would probably have been boarded to aid weatherproofing.

 

[AndrewB]

Thanks guys.

So I got the big ladder out and faced my fear of heights. Do we think that little lift on that tile would be enough to let a bit of wet in? Also went into the attic in darkness with daylight outside and there is the slightest sliver of light.

I often see the phrase here 'drafty roof is a healthy roof'... But is light getting in where we draw the line?

 

[a twig]

At the risk of being the bearer of bad news, slate can become porous…

Repair or Replace a Slate Tiled Roof - The Important Factors To Consider

Expertise and advice on whether it's time to repair or re-slate your slate tiled roof. Burton Roofing Merchants guide, information and tips.

www.burtonroofing.co.uk

This article is actually quite useful in explaining some of the issues you might be facing

What should you be looking for​

When looking for problems internally, water damage to ceilings will probably not be under the problem area on your roof.

Externally looking for broken, slipped or missing slates might be harder to do. But if possible you need to know whether they are all in one area or scattered across the entire roof. If the damage is all in one area, the problem might be with the anther aspect, a chimney flashing perhaps, rather than the roof.

Check loose slates for firmness. The best way is to hold a loose single slate at the edge and gently tap it in the centre with a hammer. It should produce a clear ringing sound if the slate is sound. If you hear a dull, dead, sound it’s likely that the slate has become porous and is past its usefulness.

As a guide if 20% of the original slates have been renewed, and repairs are scattered all over the roof, further repairs are considered to be no longer cost effective. Factors including the state of the gutters and ancillary items, like flashings need also to be considered.

 

[AndrewB]

Thanks for the info. Are you suggesting that just that one slate may have become porus? Or perhaps that it's split into layers and that's what's causing the small gap?

We did have nail sickness mentioned in our building survey on purchase, so are somewhat financially prepared to renew the roof. I'm not sure we're at that point though?

We do see some dark patches on the lath behind the iron nails (see above), but I am generally expecting to make a repair or two over the next few years and full replacement after that.

If we're talking about perhaps replacing that slate, then I'm thinking that my solar panel roofers may be able to tackle it when the scaffold is up.

 

[Stevers]

Your roof actually looks to be in pretty good shape for a 'nail sick' roof, and as it's not felted it is likely to be original. The average life of a slate is said to be around 140 years, so yours may be life expired, and some of the slates will be worse than average for their age. The lack of tingles suggests to me centre nailing, so slightly less cover in the event of a leak. My roof (from 1879) was redone in 1997, when it was also felted. With hindsight rather too many of my slates went back, though using hooks, and I think you can safely assume that your roof is more fragile than it looks. Having done some of my own roof repairs and seen how weak old slates can be up close, I wouldn't want solar panel wallys on my roof, even now it's felted. To my way of thinking it would be better to redo the roof as part of the solar installation not afterwards - and only one set of scaffolding required. I can't help thinking that if you have leaks now, you'll have more leaks once weakened slates have been disturbed by a solar installation, and no safety net of it being felted.

 

[Lacan07]

If that roof isn't felted it can't be that difficult to trace where the weak spots are during a rainy day. Most people don't have that luxury, one of my roofs has 2 layers of felt and lath & plaster blocking the view!

Unfortunately though I think Stevers is probably right, beware unsympathetic tradesmen making it worse.