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Property/DIY

HELP! Massive condensation in loft

21 replies

vj32 · 07/12/2014 15:50

We have just had the loft boarded to provide storage. It is really well insulated. Now the weather has got cold we have just discovered a massive condensation problem in the loft, so all out things are going to be ruined. What can we do?? We have had so many problems with this house already, including the boiler breaking last winter and problems with a plumber, changing the locks etc even though it supposedly needed no work doing. I'm starting to want to move...

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EnlightenedOwl · 07/12/2014 15:57

You say its been boarded and well insulated...my first thought is air vents have been blocked and this has caused the condensation.

vj32 · 07/12/2014 16:23

I thought that too and went to look and can't see any air vents at all.. at our last house they were obvious, you could see daylight. I don't suppose its a different roofing material or something. The insulation is about a foot thick (previous owner qualified for one of these free insulation grants as she was a pensioner.). Do I need to pull back the insulation?

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VivaLeBeaver · 07/12/2014 16:26

Yes its lack of ventilation.

The insulation I believe should have a slight gap round the edge to help.

My neighbour has a similar problem and has had a builder round who has said they can put vents in, I believe in the roof tiles, at a cost of £50 a vent.

EnlightenedOwl · 07/12/2014 20:04

I know with mine I've got grilles in the soffits to allow air flow and I know when they put the insulation down in the loft they left a clear margin to allow air to flow and ensure those vents weren't blocked at all.

Sandthorn · 07/12/2014 20:27

We had to leave a 6" gap around the edge of the loft so it didn't block the existing ventilation around the eaves.

TeddyBee · 07/12/2014 20:37

Yup, we can see daylight all around the edge in our new loft (on the extension) and we have little vent tiles too. Loft is freezing, but rooms below are toasty warm.

PigletJohn · 07/12/2014 21:56

water vapour is lighter than air (hence clouds) so it will rise through the house until it either escapes through ventilation, or it finds something cold to condense on.

Can you see black roofing felt in the loft, under the tiles?

If you crawl into the eaves and remove the insulation and/or boards, can you see daylight?

Are there holes in the ceilings, e.g. for downlights or pipes?

Do you drape wet washing around the house or over radiators?

PigletJohn · 07/12/2014 21:58

...and how is the bathroom ventilated?

TheFirstSolo · 08/12/2014 01:01

Oooh! can I also ask a question about this please?

My roof seems to be damp (little collective droplets on the tiles as you view them in the loft). The papery cover that is/was between the rafters and the tiles seems to be falling down into the loft; sort of tearing and hanging down. I also keep finding pieces of roof tile in my loft where it appears to have broken off and fallen in.
I have no good insulation; it's all really old and really thin, but I was hoping to lag the roof rather than the floor as it's a low loft and I need the storage space.
Does this wet sound like I need new lining or a new roof? it's around 60 years old.

PigletJohn · 08/12/2014 01:22

yes.

but also please answer the questions above

specialsubject · 08/12/2014 08:46

get on to the installers who have blocked something. This isn't right. I had stuff in a loft for 8 years (out of country) and it was fine - good draughty loft!

stuff in lofts should be in plastic crates with lids anyway.

TheFirstSolo · 09/12/2014 01:37

Can you see black roofing felt in the loft, under the tiles? *No. There doesn't seem to be any.

If you crawl into the eaves and remove the insulation and/or boards, can you see daylight? Can't answer that yet

Are there holes in the ceilings, e.g. for downlights or pipes? No downlights or pipes through the ceilings

Do you drape wet washing around the house or over radiators? Only in the extension which has it's own roof. They are over an airer away from the radiator, but in a room with a radiator which is only on for about 4 hours a day.

PigletJohn · 09/12/2014 06:17

If you can actually see the exposed undersurface of the tiles or slates, then your loft should be pretty draughty/well ventilated.

Or are you in Scotland with Sarking boards?

TheFirstSolo · 09/12/2014 14:20

Not Scotland no. SE England. Just Googled Sarking boards and that's a no too.
No draughts that you would notice in the loft. It's always freezing up there in the winter and sweltering in the summer. No damp affecting the contents up there from what I can tell either yet !

PigletJohn · 09/12/2014 15:00

OK

Modern roofs often have ventilation tiles fitted on the slopes or along the ridge. If you house is being re-roofed, these can be included at negligible additional cost if done at the same time. Modern roofs also use a permeable (breathing) membrane instead of the older felt (or in your case, it may have been tar-paper). A loft should be draughty (= well-ventilated)

If you are getting condensation inside an unfelted roof, there is probably excessive water or vapour getting into the loft. Are there any water-tanks up there, and do they have close-fitting lids, and are they bitterly cold? The more common causes I mentioned earlier. There might also be a bit of a leak, but if so, the condensation would clear during a dry wintery spell, and come back after rain. If it is worse after a hot steamy bath or shower, then steam is rising up through the ceiling, usually through cracks, gaps and holes for pipes and lamps.

TheFirstSolo · 09/12/2014 17:36

:) Thank you thank you so much! PigletJohn
I do have a large water tank up there and I did move the (heavy and lagged ) lid in the summer. I'm wondering if I haven't quite put it back snuggly...
I will check this.

I don't have ventilation tiles in the roof or on the ridge tiles.
I'm looking at putting Celotex between the rafters to give some kind of insulation without having to have the loft floor done (need the storage space) as it's a low-ish roof. I'm hoping this will sort the problem out. Good idea or not do you think?

PigletJohn · 09/12/2014 19:19

foam slabs between the rafters is an expensive way of insulating a non-habitable storage space. It will also block ventilation through the gaps between the tiles.

You might consider laying rigid foam slabs on the loft joists and laying flooring over them. There is a descriptive brochure from Knauf. They call it loft decking. Foam is much more expensive than mineral wool, but is a better insulator.

here we are. I might do my own. The surface area of the floor is about half that of the two roof slopes, so you need less material.

PigletJohn · 09/12/2014 19:21

I did see a Knauf slab without its own chipboard layer, which might be better value, in a brochure.

PigletJohn · 09/12/2014 19:25

Space Board Eco, it seems to be.

TheFirstSolo · 10/12/2014 00:44

Brilliant! thank you again.

Thank you OP for allowing me to interrupt your thread :)

vj32 · 10/12/2014 11:45

We are planning a full on attack on the condensation - dehumidifier arriving today (I use cloth nappies so have to dry some washing in the house!), hopefully getting a builder to check ventilation in the loft as I can't find any, and extractor fan going in the bathroom. Sadly that means we can't fix our broken downstairs toilet. (Which has been broken for about 6 months and needs replacing.) Unexpected bills are the worst! Thanks for the help.

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