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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    Can anyone help with recent experience of meeting fire regs in a cellar?

    I'm installing drainage membrane and perimeter drainage to deal with moisture, and insulating with 50mm PIR below a floating floor and 50mm on C-section metal studs to the walls to make drier storage space. Ceiling (floor of room above) has 180mm of flexi wood-fibre with a lambda of 0.039W/mK.

    Approved doc B suggests I need 30 mins FR. I had planned to use 1 x 12.5m Gyproc Fireline, skimmed, to walls and 2 x 12.5mm to ceiling. Does that seem right to any of you who have recently done similar work? Part of the cellar was 'converted' to a 'garage' over 30 years ago by a previous owner (B. Regs approval applied for, although not sure if it was ever signed off), and the ceiling they installed was 2 sheets standard 12.5mm pl'bd, skimmed. That was installed badly, and has been removed.

    I may have to download the 'White Book' from BG, but it sounds like that may contain more info than I can process!

    Thanks in advance for your help.

    • CommentAuthorFred56
    • CommentTimeMay 15th 2020
    Depending on your ceiling joist spacing one layer of 12.5mm BG Fireline should meet the requirements for 30 mins. Two layers would give 60 but unless this is a separating ceiling (between premises or demise) the English req is 30. The white book is quite good at this stuff and I often include the white book reference when writing up a job spec. You have to make sure you comply with the spacing, have perimeter battens and noggins. If you you use the 15mm board the joist spacing and noggin requirements are a bit more generous. Stick to the system, right fixings, fixing schedule and all the right finishing materials exactly as the product certification. Avoid the Siniat option, they specify their own huge screws. Siniat has a 60 min cert for one layer of 15mm but I tend to avoid putting it in a spec because contractors will weasel their way to save every penny they can and may not follow the rather exacting certification details.
    On some jobs in old buildings we spec for a grid of Gypliner hung off the joists. It ensures you can fulfil the spacing requirements. Old buildings often have irregular joist set out and levels can be all over the place. Also spaced for 1800 x 900 boards as the access to basements can be tricky for adult size boards. Sound reduction is improved too.
    Thanks @Fred56!

    I went for 2 sheets of 12.5. I have noggins at perimeters but not at every board-end; however I do have 2 x layers with staggered joints. Most of my (180-ish by 75-ish) joists were at 300+ ctrs, with a rogue couple at 450.

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