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Acoustic performance, floor thickness & Part E - Green Building Forum


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Acoustic performance, floor thickness & Part E

A long storey but my project started out as an extension & refurbishment but has turned in to a new build due to old foundation constraints... I have planning permission for a certain height building and the room heights worked out OK (2.35m) but I had not accounted for Part E as it wouldn't have applied. I factored in a first floor thickness of 300mm originally but it now seems I need to make it 415mm if following robust details (RD). I want to maintain the ceiling height and cannot make the building any taller (neighbours and council objected to planning and pre-apps for taller buildings were all negative) so would like to know if there are any innovative ideas to meet Part E without going to the extent of RD?

I plan to use metal web joists @400cts and 256mm deep.


  • Are you having a separate flat above the floor?
  • Its just a single domestic dwelling, so no separate flats etc.
  • I found some information on HHBC website that says detached dwellings do not have to be tested. As my build is a single detached dwelling I guess it doesn't have to be tested. However, I would still like to know if I will be expected to build to RD levels but without the need for formal testing?
  • best bet is talk to your building control man as a lot of the things can be are at his discretion as the "approved documents" are only guidelines as to what is acceptable, not a definitive list.

    We had similar (extension ended up as a new-build) and a lot of the things such as acoustic testing were waived as long as he was happy with principle of what we had done.
  • edited January 2015
    The idea is that if you build to an RD you don't need a sound test. Some BCO will allow small modifications to an RD but some are quite fussy.

    As the floor is between parts of the same dwelling you only need meet part E2 (Table 0.2) not the more difficult E1.

    Perhaps see...,d.d2s

    On page 4 it suggests that you can meet E2 using..

    "Timber joists, engineered I beams or steel joists with floor boarding having a mass of at least 15Kg/m2. Ceiling lined with 12.5mm Wallboard TEN. 100mm Isowool General Purpose roll or similar in the cavity, all joints to be well sealed."


    "Timber joists, engineered I beams or steel joists with floor boarding having a mass of at least 15Kg/m2. Ceiling lined with a double layer of 12.5mm Wallboard, all joints to be well sealed."

    No mention of the depth of the joist other than the need to fit 100mm isowool on the first option... but check for any small print I've missed. Discuss with your BCO.
  • ward32,

    Are you building detached, single dwelling? If so, why are looking for Part E solutions?

  • I'm pretty sure Part E applies to a detached single dwelling. It did to mine.
  • Thanks for the replies. I found the references in BR thanks to CWatters. It appears that within a single dwelling 40db sound reduction is required and can be met with either one layer of 12.5mm plaster board, acoustic insulation and single floor layer of 15KG/m2 OR two layers of plasterboard, no insulation and the same floor covering.

    Worry over, I can continue as I was going to use at least two layers of plasterboard - thick carpets and underlay.
  • ... never had a sound test request for a single det dwelling.......!
    ward32, I would ask your BCO/BCB before you spend any money.

    Good luck:smile:
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