Damp joists in loft

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Andrewd8323

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Hi all

Hope you're well.

I've just had my house re-roofed (new membrane, new battens , new thin edge sandtoft concrete tiles, and new dry ridge system).

Following rain, the wooden rafters are getting damp in some areas (always the same recurring spots).

When the rain stops and we have a dry day or two, the woodwork then dries out.

I've been in the loft during heavy rain and weirdly, I can't see any water drops coming in or any water flowing down the rafters. However, once it is has been raining a few hours the timbers have visible damp spots, are damp to touch and are showing elevated readings on my damp meter. I'm therefore wondering if the water is slowly penetrating the wood via nail holes or something (e.g. where the battens are attached to the rafters)?

I've set out a couple of videos below:

  • The first video here shows the wood dry, with low readings from the damp meter

  • The second video here shows the wood damp. As soon as the video starts you can see clearly that it is damper, and the damp meter then confirms this.
The roofer who did the work has been round and said that because we can't see water drops coming in, the roof must be fine. He is totally ignoring the damp marks / elevated damp readings etc. However, I'm concerned that if I leave the wood to keep getting damp each time it rains it will eventually rot / get mouldy.

It's all getting quite tense as I've only paid 75% of the roofer's bill so far. I don't want to pay the remaining 25% until I'm comfortable the roof is watertight, but he is threatening court action as he is claiming the roof is fine.

Have you ever seen anything like this before, and, if so, what was the cause? I'm in a difficult position with the roofer at the minute where he's saying "everything is fine, pay my bill" and I'm saying "it can't be fine, the wood is getting damp" and we're not making much progress, just going round in circles.

Thanks

Andrew
 
Can you uncover the tiles above the damp area and see if there is any tears in the felt or other faults etc ?
 
Hi thanks for coming back to me. They've taken the scaffolding down now so it is difficult to get up there and the roofer isn't willing to investigate the source of the damp unfortunately.
 
You may need to instruct another roofer to do so then and if the result is a fault by roofer No. 1 then you can rightly deduct the cost from the 25% you are holding.
 
Difficult to tell, the video is all over the place. Can you put up some pics showing the context i.e the wider roof structure from inside. It looks like the felt has been stapled in places and is loose elsewhere.

Blup
 
Is there by any chance a roof valley or some other smooth surface in contact with the membrane above that beam (hidden from view)? If so then I wonder if condensation is an issue, rather than an actual leak. What rings alarm bells for me is the fact it happens worse after rain - I have an issue in my loft with condensation on a plastic roof valley, which is always worse after rain. I also have that same type of white membrane in part of my loft.
 
Hi all

Thanks for your responses and sorry for the slow response - I've been away and things have developed somewhat.

I haven't made any progress on the damp joists, but as per @blup 's request i have put a video here showing more details of the inside of the loft. Hopefully that's helpful. Any suggestions gratefully appreciated. In response to @Owen74 's question - there isn't anything unusual above the affected areas - just a dry ridge system on the hip and tiles above the other areas.

The development I've had is that:
* I've had another roofer round to look at the roof
* This new roofer wasn't able to help too much with the damp woodwork (they said they would need to erect scaffolding and take the hip and ridge tiles off to work out what was happening)
* But while he was here he said "what I can tell you though is that the flashing has been done wrong on the chimneys given the roof tile that's been used"
* I then took a photo of the flashing and sent it to the tile manufacturer, who agreed it hadn't been done right and said soakers needed adding as flat roof tiles have been used - I've attached photos of the flashing (see 1348 and 1349 below)
* Since then, we've had plenty of rain and we've had damp marks develop on the chimney breast in our bedroom - I've attached a photo of this (1490)
*I've also been in the loft during heavy rain and the chimney breast has been wet to touch - video here
* The roofer who did the original work came round today, peeled back the flashing and essentially said "there is no evidence of water getting beneath the flashing, the roof is all fine. Moist air must be entering the loft from the house then condensing on the chimney breast and running down into the bedroom beneath. You need to insulate the floor of the loft better and less moist air will get up there".

I'm feeling at a bit of a loss now. I'm struggling to believe that it is condensation given we've been told by two other parties that the flashing has been done incorrectly. The size of the staining and amount of water also seems high for condensation. Finally, we have a dry hip / ridge system, breathable membrane and vented eaves trays, so I would have thought there is enough ventilation up there to prevent significant amounts of condensation.

So this is just a broad plea for any advice really - any suggested next steps?! What would you do? Do you think it could be condensation?

The only possible next steps I can think of are:
1) Ask the roofer to fit some vented roof tiles to increase airflow - if the problem still happens after this then surely it can't be condensation.
2) Insist the original roofer does the flashing as per the manufacturer's instructions

Thanks all

Andrew
 

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Can you take a picture closer to the hip on the outside ?
I can see it's dry fix but I don't see hip trays .
Close up will tell all
 
Andrewd8323 said:
Hi thanks for coming back to me. They've taken the scaffolding down now so it is difficult to get up there and the roofer isn't willing to investigate the source of the damp unfortunately.
Click to expand...

You need to threaten to take the roofer to court to get him back
 
No harm in improving insulation regardless, if nothing else it rules out that as cause.
 
Murdochcat said:
You need to threaten to take the roofer to court to get him back
Click to expand...
He has now returned but he is saying that condensation is the cause of the problem and the roof is fine.

However, based on the amount of water I'm seeing on the bricks in the loft and the extent of the marks I've got on the chimney breast in our bedroom, I'm struggling to believe this (my post yesterday from 8.58pm had links to videos and some pictures).

In addition, I've only seen the chimney in the loft get wet during periods of heavy rain. I went up there yesterday morning (which was a very cold morning with no rain) and the chimney was dry to touch. If this was a condensation problem I would have expected it to be wet on a day like that as the bricks were very cold. So I'm really struggling to believe him.
 
Andrewd8323 said:
He has now returned but he is saying that condensation is the cause of the problem and the roof is fine.

However, based on the amount of water I'm seeing on the bricks in the loft and the extent of the marks I've got on the chimney breast in our bedroom, I'm struggling to believe this (my post yesterday from 8.58pm had links to videos and some pictures).

In addition, I've only seen the chimney in the loft get wet during periods of heavy rain. I went up there yesterday morning (which was a very cold morning with no rain) and the chimney was dry to touch. If this was a condensation problem I would have expected it to be wet on a day like that as the bricks were very cold. So I'm really struggling to believe him.
Click to expand...

Hi there, been looking at this and have some more thoughts. Note, I'm not a roofer but a fellow sufferer of 'roof anxiety'. :)

Just to explore the condensation idea fully before totally dismissing it....

Have you pulled back lagging from soffit vents to maximise ventilation?

You said it happens in specific areas only - could these be the coldest spots of your roof surface and/or warmest areas of loft?

Could you keep a thermometer/humidity monitor up there and check it during the good vs bad times? (I use DOQAUS Digital Room Thermometer, £12 off amazon for pack of 3).

One thing I've learned is that during rain the roof surfaces get colder. And that condensation can produce a LOT of water during those times.

I notice your wet chimney brickwork (inside loft) is very close to the roof surface; a possible 'warm spot' in the loft, with possible 'cold surfaces' in that warm spot (cooled by rain). And viola, warm air with cold surface = condensation. I can see how that may drip into wall over time.

Could you somehow insulate that bit of 'cold chimney'? Either with lagging or something else? I've had some limited success protecting a cold plastic surface in my loft against condensation using 2-3 layers of SuperFoil. Could it work for that little area of brickwork I wonder?

(Disclaimer: I'm not a roofer, I don't know what I'm talking about, and this might be a terrible idea).
 
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