Condensation or leaks

[mdm67]

OK I have read all the post on leak v condensation, I have a few roofers out and keep getting different opinions. I have damp sarking boards in one area in my eves, not dripping but moist to the touch, the moist boards even frosted up in the cold weather a week or so back. Question is leak or condensation. Its a slate roof, pretty old about 90 years but been well maintained. Sofits are clear and ventilated with holes every 18 inches or so. The area has very good insulation as you can see from picture so not sure how much if any of house heat is getting in there. I pushed a screwdriver in to a damp sarking board and it seems pretty dry inside. The dilemma I have is its kind of a uniform dampness unlike previous leaks which tended to track down the pitch of the sarking boards north to south or down the joist, this looks more horizontal pattern. No ridge vents buts its cold up there and has a draft.

Untitled

• mdm67
• 17 Dec 2012
• 1

Untitled

• mdm67
• 17 Dec 2012
• 1

Untitled

• mdm67
• 17 Dec 2012
• 1

 

[big-all]

the usual contenders really
down lighters/spots pipes and holes around extraction badly set up water tanks
what is near the the areas

 

[mdm67]

None of the usual suspects live in this bit of the roof, no tanks or water pipes, nor down lighters or extractor fans, in that area of roof...below is a living area with two radiators but that is no different to rest of house/eves..i did have boxes piles high which I have laid flat now, did that a couple of weeks back but still sarking the same

 

[foxhole]

Wind blown rain will find any loose tiles and dampen the boards, nothing to be concerned about if you are sure tiles are sound.

 

[mdm67]

thanks for the feedback, what i dont get is its such a big area, looking at the 1st picture you can see its about 6 boards up and its across the 3 areas of joists.....Its ok for the boards to be damp then?

 

[Alastairreid]

It is condensation! I would consider installing vents at high level both front and rear.

And no it's not a good idea to allow the sarkin boards to remain damp for prolonged periods.

Even though it feels cold and airy there still needs to be air circulation to vent properly, you wont get this with vents to eaves with nothing higher up.

This type of thing.

 

[mdm67]

thanks, I think I will give that a go, just need to find a roofer to install a couple of vents, my gut feeling is condensation but to say I know nothing about building/roofs is putting it mildly

 

[mdm67]

How many slate vents and how high? I haws thinking 2 slate vents on each side about 1/2 to 3/4 ways up the roof pitch? What do you think, I have a roofer to do it but he wasn't 100% sure...seems to be a bit of a black art

 

[Alastairreid]

The vents go in as high to the ridge as possible!
Normally 2 or 3 courses down from the ridge.

I would get a roofer who knows how to install them properly as well.

 

[joe-90]

It is condensation! I would consider installing vents at high level both front and rear.

And no it's not a good idea to allow the sarkin boards to remain damp for prolonged periods.

Even though it feels cold and airy there still needs to be air circulation to vent properly, you wont get this with vents to eaves with nothing higher up.

This type of thing.

Aye - the Venturi Effect in action again. You are learning Grasshopper.

 

[joe-90]

It is condensation! I would consider installing vents at high level both front and rear.

And no it's not a good idea to allow the sarkin boards to remain damp for prolonged periods.

Even though it feels cold and airy there still needs to be air circulation to vent properly, you wont get this with vents to eaves with nothing higher up.

This type of thing.

Aye - the Venturi Effect in action again. You are learning Grasshopper.

 

[mdm67]

will let you know how it goes, the guy doing it has done work before up there so lets see..

 

[Alastairreid]

It is condensation! I would consider installing vents at high level both front and rear.

And no it's not a good idea to allow the sarkin boards to remain damp for prolonged periods.

Even though it feels cold and airy there still needs to be air circulation to vent properly, you wont get this with vents to eaves with nothing higher up.

This type of thing.

Aye - the Venturi Effect in action again. You are learning Grasshopper.

aaah i had good teecha o wise one