Wet bedroom walls- Condensation?

Jeepers_Creepers

You certainly wouldn't want to re-roof the house!

I can only go by the info I have on here. I don't know, for example, if there's any ventilation currently in that roof? Are there any gaps at all along the eaves? Any gaps on the back roof?

Assuming that the ventilation is very poor indeed - the slates are pretty much sealed and draught-proof, and the gaps at the eaves are tiny - then all I can do is suggest that, if they are doing this at all, it would surely be worth fitting 2 vents at the back as well?

You NEED to have a flow of air going right through that roof space, air flowing IN and air flowing OUT, ideally at the furthest away points from each other. I wonder - just how much air would flow through one vent and out the other when they are both on the same side? I suspect not a lot, so I therefore suspect their effectiveness will be limited.

You've probably seen a few threads on here with folk suffering condensation in their bedrooms? Where does the worst condensation appear? Mainly in corners, and along the ceiling lines. Why? Largely because that's where there's less air flow. The air is relatively stagnant there. If you were to drill a hole in the ceiling right in a damp corner, the damp would soon dry up from the howling draught shooting up that wall :-)

I wonder how much two additional vents at the back would cost - perhaps only £100 more since they are already there.

I know what I would ask for. BUT I am not a roofer :-)

stuart45

I would agree with above that 2 at the back would be useful. Maybe the access is a bit more difficult?

Arsenal2019

No, there’s not any ventilation installed in the current roof. I would say the gaps between the Eavs is very small. 

My dad stated slotting kingspan insulation between the timber and the slates, going down parallel with the roof itself? He said maybe that was any water / condensation would then fall from the slates onto the kingspan, and then into the cavity? But I  can’t see this been any good?

and okay. So you two are saying two at the front and two vents at the back too?- even tho I don’t have a problem at the back?? (No there is no issue with access around the back)

Jeepers_Creepers

Fitting insulation to the underside of the slates would not only be a waste (it wouldn't 'insulate' anything useful - there's no heat in that roof space to insulate), but it could reduce air flow above it even further, so that any condensation that could form between it and the slates will stay there to do potential long-term damage.

You don't not have a problem at the back, just like you don't have a problem 'at the front'! You have an 'attic space' problem in general, and the only reason it SHOWS at the front is because that's where the condensation trickles down to! You need to flush out the damp air from that whole space. For that you need a cross-draught - in one end and out t'other.

I think it's worth asking the roofer how much more back vents would be.

stuart45

Yes, eaves to eaves ventilation would be good. Eaves to ridge is also good as well, although not always needed. 
Eaves to eaves relies on the wind to some extent, whereas eaves to ridge does not. 
Ridge venting alone is worse as wind can have a negative effect and suck air out, which in turn can bring up more damp air from below. It may be the case with just a few vents on one side where air is sucked out when the wind is on the lee side.
This happens with air bricks sometimes if they are put in the wrong place.

Arsenal2019

Okay, so what you are both suggesting is to have a vent at either side of the roof. Front and back of the house?

Jeepers_Creepers

TWO vents either side - do it proper, like

Both vents at low level - basically as low as possible.

I think, without question, it's what I would have done if it were mine. You have a lovely looking house, with a very nice roof - let's keep it that way...

Arsenal2019

Gotcha! Okay I’ll put that idea forward then and see what the roofer says.

Honestly, thank you both very much for your help !! 

missile

Have you checked the guttering?

Jeepers_Creepers

missile said:

Have you checked the guttering?

She's had a few folk round to look at it, and we're assuming that all such obvious causes have been eliminated.