My roofis sound and sealed. Loft floor is insulated and boarded. Some carpet down on top of boards. Loft used as storage (loads in it). We have noticed since cold weather came in that loft is damp. After the hatch is down for a short time condensation is visible on the underside of the roofing felt. It then collects and runs down (and of course drops down onto whatever is underneath).

What causes this. Ive never known it before. Keen to solve as its starting to damage stuff stored up there.

Is it possible that insulation has been pushed too far into the edges? Does there have to be ventilation from soffits into the general loft space?

There should be ventilation - a local builder who did some work for me said that he did a steady line in installing air-bricks in lofts after people had sealed up all the old vents.

When my old warm air central heating system was removed I was left with a ridge vent - I asked the builder what I should do with it (e.g. remove or block it) he said to stuff some perforated zinc mesh up it to keep the bugs out, and leave it open to add ventilation.

If you look up under the edge of the roof, behind the gutters, you should see a number of vents. These should be clear to allow air circulation.

[Edited on 14/1/09 by David Jenkins]

Yup, you need some ventilation.

Basically the warm moist air from the house is getting up into the loft, where it meets the cold roofing felt. The moisture then forms on the underside of the felt and runs down towards the walls, but usually drips off into the middle of the room.

You need a combined approach. What is your loft hatch like? A bit of hardboard in a timber frame, or is it an proper insulated hatch with a seal around the frame? If it is a bit of hardboard, upgrade it, so it latches shut onto a draught seal around the perimeter. Consider changing to MDF with polystyrene stuck to the back of it.

Then ventilate the loft. I used roofing slate ventilators from Screwfix

http://www.screwfix.com/prods/45984/Building/Roofing-Insulation/Alpha-Slate-Vent

(assuming you have a slate roof) but you'll probably need a roofer to install them for you.


Check out

http://www.buildingconservation.com/articles/condensation/condensation.htm

Look for interstitial condensation.

HTH

Mike

Ours has eave vents and some vented tiles about 2/3 of the way up the roof slope and when it's windy it sometimes rattles the ceiling hatch. It sounds like you are missing some.

Im a LOFT ENGINEER!!

Well thats what my gran tells every one, i actually Fix Lifts, but havent the heart to tell her

Some good advice that confirmed what i thought.

On closer inspection ;

Ridges - other houses in area have ventilated ridge tiles - our street doesnt. No houses in our area have ventilated roof tiles (30 year old houses) but on an extension i had built 5 years ago (old house) i had to install some to comply with regs.

Soffits - mine is still old timber ones. It looks like some one has drilled 7off 10mm holes along the length. Knowing that ive seen ventilated soffit boards before and that you can buy ventilators id say mine are very unsuitable (too small and too few).

Loft insulation - whole loft is insulated and boarded. Of course i cant inspect the insulatio due to boards and stuff up there. I will however have a closer look soon to see if the insulation has been stuffed into the corners - i guess it shouldnt be (ie a gap from the soffit ventilators into the roof space.

Loft hatch - yep - i fess up! It is a bit of hinged ply with no rebated sealed bits around the edges. No insulation on top either. Also the hatch is in landing area, right outside bathroom. I guess when shower / bath is being used it is very easy for hot damp air to make its way into loft space. Ive seen you can buy proper insulated hatches with surrounds - might have a look at sizes.


Walls have cavity insulation too - ive heard addition of this can lead to loft condensation issues due to restricted airflow.




Im thinking easy solution is;
1. New hatch.
2. Clear insulation and boards from corners of eaves,
3. Soffit ventilators (1, 2 and 3 very easy to do),
4. If that doesnt solve add ridge or tile ventilators so the air from soffits has somewhere to circulate to.

How does that sound?

Options 1 - 3 should fix it.

My loft hatch is the same - it's hinged, with a ladder above that can be pulled down. Making a seal would be easy, but it's one of those 'round tuit' jobs...