Water marks in loft

[Aurelio]

Hi,

I’m looking for some advice, I recently was in our loft and noticed water marks on the boarding, on different areas. I’ve checked for any holes in the roof and can’t see any, it is very cold in the loft. It was fully boarded a while ago with gaps left around the eaves. The underlay appears to have condensation so I’m assuming it could be caused by lack of ventilation.

Should I be concerned and what would you recommend? Should I leave it to dry, perhaps with a dehumidifier?

Many thanks

 

[malcolm]

Looks like dripping from condensation forming under the roof. What happens is warm air from the house finds it's way into the loft and water condenses when it hits a cold surface. Fixes are trying to reduce air gaps from the house into the loft and increasing ventilation in the loft.

The membrane doesn't look breathable, and a breathable membrane isn't enough anyway. The loft ought to have eaves ventilation and a decent wind blowing through to keep it dry. Does it have any ventilation at the moment?

 

[Aurelio]

There is a gap between the eaves and boarding and the insulation is underneath, I am planning on inspecting it again tomorrow, but I can’t see any vents. I guess the answer is to improve ventilation as you say, how should I do this? The loft latch is insulated too. I had wondered if there was a leak due to the water marks, but do you think this is caused by the condensation?

I’m just wondering how to tackle it. I am planning on moving everything out tomorrow and drying it down. Any advice would be appreciated.

 

[Jahouli]

Hi Aurelio

If you google 'lap vents' you'll see some cheapish vents which can be inserted into the bitumen felt joins. I used these in my loft to improve ventilation. They work by holding the felt apart at the join. If you are interested in using them then it would be worth measuring between the timbers to be sure they fit. Vents on opposing sides of the roof would give cross ventilation.

 

[lizziecupcakes]

Hello, I use those vents mentioned above. I have ventilation blocks in my tiles which I think are probably enough but we added the vents just incase. They are quite cheap on amazon.

This guy explains it well and had a link to Amazon in the description:

 

[Aurelio]

Thanks for getting back to me, I have just installed the lap vents and will monitor. Unfortunately I have just noticed a very small rip in the felt and can see light through it, any idea how to fix this? Can I patch repair it from the inside?

 

[Cubist]

The best repair would be to slide a new over-sized section of new felt between the damaged section and the tiles and fold the top couple of inches back over the inside face of the damaged piece to hold it in place. If you're concerned the new piece might slip past the damaged area you can glue the lapped edge in place with a little bitumen paint.