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Loft Conversion

Ventilation holes needed in ridge board...?

Anonymous user 23/02/2024 - 3.35 PM

Hi, We're planning a full loft conversion for sometime in the future and would like some advice please. I'd like to add Kingspan or similar insulation board between the 4"x2" rafters with 400mm centres in our loft which has a pitched roof. I am aware of the 50mm airgap that's required between the board and the roofing felt. Should I drill holes in the ridge board to allow air flow from the eaves and through the ridge board? If so, how many and what size? Thanks, Mike

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4 Answers

Anonymous user

Remove the ridge tiles cut 20mm of the felt either side of the rafters and replace the ridge tiles with a vented ridge tile system. Air flow will move around the ridge board on both sides of the roof. Make sure your pir insulation is very tight between your rafters or on a stormy night you will have these boards rattering keeping you awake. This is a common mistake from inexperienced loft converters. To correct it means removing plaster board and pir over the rafters and redoing, an expensive mistake!
Answered4 September 2020
3

Kent Conversions

Rating: 5 out of 5
Abingdon
the requirement for loft conversions is the equivalent of 25mm continuous air flow at the eaves and 5mm continuous at the ridge easily achieved using soffit and or tile vents and ridge vents ( tile and ridge vents have different air admittance properties so check the value to minimize the number of vents needed)
Answered23 November 2020
1

TS Carpentry

Rating: 5 out of 5
Hereford
Soffit vents cheaper and less work and cost less Do same ventilation
Answered23 November 2020
1

Anonymous user

This is dependent on the height of TheCurrent roof if there is a void above the new apex collars or above the flat roof this is adequate cross flow ventilation and no drilling would be be required if the roof is to low then I agree with the provided answer provided above
Answered23 November 2020
1