Damp in loft

[jethro_uk]

Hi all,

we had our loft re-insulated last year, back in March. I have since noticed that it is starting to get damp up there (condensation on the underside of the sarking felt). On the basis that in the past 3 years it's been bone dry, I am assuming that the insulation is now preventing the natural damp from drying.

At present, there are no soffit vents. Could I simply cure the problem by installing a few ? If so what is the best spacing ?

Alternatively I have seen you can get these roof vents which replace a tile, can anyone comment on whether these are a viable alternative ?

Thanks in advance

[Christian McArdle]

I'd go with the soffit vents, as they are less visible from the outside. They should cure the problem.

Christian.

[Bob Mannix]

As to spacing, I believe the total area of vent should equate to a 10mm gap all round IYSWIM ie if the total length of soffitt is 20m you need a total of 200,000 mm*2, or 0.2 m*2.

Bob

[Dave Fawthrop]

| Hi all, |=20 | we had our loft re-insulated last year, back in March. I have since | noticed that it is starting to get damp up there (condensation on the | underside of the sarking felt). On the basis that in the past 3 years | it's been bone dry, I am assuming that the insulation is now preventing | the natural damp from drying.

You are no longer heating the loft, with stray heat from the house, which probably evaporated any condensation. =20 | At present, there are no soffit vents. Could I simply cure the problem | by installing a few ? If so what is the best spacing ? |=20 | Alternatively I have seen you can get these roof vents which replace a | tile, can anyone comment on whether these are a viable alternative ?

I would use soffit ventilation to get rid of it. I have just had mine re-done and there is now at least 18 sq ins of ventilation per yard. It would be difficult to exceed that.

--=20 Dave Fawthrop

17,000 free e-books at Project Gutenberg! Yorkshire Dialect go to

[Set Square]

It's probably just down to needing decent ventilation - but do make sure that you haven't got a condensation-making machine in the attic - such as a central heating header tank which is pumping over.

[jethro_uk]

all good advice. I take it that the fact no-one commented on the replacement roof tile means they're not recommended by readers of the group ?

As it turns out, the missis called the company that put the insulation in, and they have agreed to come and inspect the loft, and if ventilation is required, they will sort it, so a right result there.

However, on a related topic, we have a cupboard which used to house the hot water tank (we went combi), and is now used as a towel cupboard. Is there any sense to installing a large (4" diameter) pipe which would act as a vent from the below-floor crawlspace to the loft-space ?

thanks in advance

[Dave Plowman (News)]

The BCO in this part of Wandsworth insists on them with a replacement roof. I've got them at the top of the roof with soffit vents too.

[Christian McArdle]

I'd ventilate at the ridge if the rafters were boarded. However, it seems a waste of time (and more importantly, affects the outside appearance) if it is all open space and you can get enough soffit ventilation.

Christian.

[dg]

If you fit any soffit or above fascia vent, then you have to ensure that the loft insulation at the eaves does not impede the air flow. It may be difficult to do this - ie fitting vent trays.

Plus, warm air may remain towards an unvented top of the loft, so you shouls also fit ridge or higher tile vents together with eaves vents

It would be easier to fit tile vents - 2 per side for a typical 6m width house, and half way up the slope.

dg

[bob]

My inlaws had their roof trim replaced by a cowboy company and they did not include any soffit vents. When up in their loft I noticed sweating patches, not damp patches. Also, on a windy day there was no air flow. Upon asking the fitters about it they became lets say rather unprofessional. They were asked to leave and 15% was deducted from their payment.I have now cut into the soffits, front and rear of the building a set of vent grilles. Basically i used a drill cutting bit, cut out a reasonable hole between the rafters and used builders silicone to fasten the grilles on. I put a vent 12" long X 6" deep between every other rafter - front and rear. It took longer to mark out where I was going to cut the holes and make sure that I was not cutting into anything else than it did to do the actual job. Nonetheless, no more sweating in the loft. Bob.

[manatbandq]

Did the roof have any vents originally?

Was their any evidence of either with the old roof trim?

Maybe they were just doing the job they had been contracted to do. When I had a similar job done the prospective contractors were specifically told to quote for fitting ventilation which was not already present.

MBQ

[Dave Plowman (News)]

They should work to current regs when replacing a roof - unless there are special circumstances like listed building, etc.

[manatbandq]

They weren't replacing the roof, only the "roof trim" which I took to mean soffits and/or facias. I would class this as a repair. I didn't think there was any requirement to update to the latest building regs when making a repair.

MBQ