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Roofing

do you need to vent a cold outbuilding roof

Anonymous user 09/03/2024 - 3.11 PM

I have a 9x5m out building newly constructed. It has thermalite bricks on the inside and bricks on the outside with rockwool in the cavity. The roof is felt. The joists are placed along the 5m length (front to back). There's nogging placed in a staggered fashion throughout, in between the joists. The joists are 9x2. There is rigid insulation jammed into, in between the joists and nogging. The nogging and joists touch the decking with no gap for airflow. There are no vents in the soffit or elsewhere. The fascia and soffit have already been fitted. Plaaterboards for the ceiling (35 boards) have already been screwed in. I am really stressed out as I have read that cold roofs need to be ventilated. Could I get away with not venting it? Warm roof would be too expensive- how much would i expect to pay if I really had t (45m2). I i had to vent the cold roof, how would I go about doing this? Would i need a 50mm gap above the insulation and drill 25mm holes at the top of the noggings? And then add a continuous vent in the soffit? What's the hest way to go about doing that? The soffits have been nailed in. Please help, your expert advice would be appreciated!

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3 Answers

Anonymous user

Hi there the builder who done the job should know that there has to be an air flow system in any roof installation.... insulation should have 50mm gap top and bottom to stop the roof sweating the flat roof should not have a vent in it but the soffits should be vented to stop all the moisture ....needs to be resolved as the plasterboards will start to go black with damp and this will cause further damage and problems

Answered18 July 2020

Severn Fibreglass

Rating: 5 out of 5

Bewdley

Hi, have you contacted person who carried out the work to see if they are prepared to rectify the situation? I'm afraid there's no easy fix to this, the insulation and noggins should be 50mm away from the roof deck. if left unchecked you will get damp in your roof and your joists will begin to rot, you will need to replace the roof eventually but will have to contend with damp and mildew on the ceiling in the meantime. I recently gave a quote for a warm roof at £125 per square meter, this is for a GRP though, I'm not sure how much a felt roofer would charge. I would advise getting a professional to remove the roof, replace the noggins and insulation, install vents into the soffit and relay the roof, you could try a legal route to get compensation for the original work to recoup the expense of the new roof if the original builder is not prepared to do anything to rectify the situation. I would also advise you to switch to a fibreglass roof, properly installed, a fibreglass roof will last a very long time.

Answered18 July 2020

MP ROOFING

Rating: 5 out of 5

Huntingdon

On roof like that you can fit mushroom vents in roof buy drilling threw deck .Fit vents in facias or soffits .The issue they often drill threw joists to increase air flow around roof so with ceiling up it may be hard .Speak to building inspectors see what they say .

Answered18 July 2020