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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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    • CommentAuthorItsBobbins
    • CommentTimeOct 14th 2018
     
    Hello,

    Im looking for further advice on how best to proceed with insulating a suspended timber floor.

    So far, the suggested have been:


    1) insulated slab

    we have around 500mm void beneath the floor. i understand we would need to build the level up with hardcore then something like sand > DPM > PIR insulation > concrete > Screed > finished floor?

    Would there be any issues with this method given the depth of the void?


    2) PIR insulation between joists

    The joists are only 50mm and most people suggest 100mm PIR. Could extra timbers be fixed to the joists at the counter batten points so allow for 100mm insulation?

    3) lay new flooring on top of existing flooring.



    Would there be much difference between options 1 & 2 in terms of heat retention? obviously there would be a difference in price!

    Would option 3 work be any good if new floor was laid with adhesive and sealed at the skirting boards?


    sorry i realise there are other threads in a similar vein!

    thanks in advance :bigsmile:
    •  
      CommentAuthordjh
    • CommentTimeOct 14th 2018
     
    Posted By: ItsBobbins1) insulated slab

    we have around 500mm void beneath the floor. i understand we would need to build the level up with hardcore then something like sand > DPM > PIR insulation > concrete > Screed > finished floor?

    Would there be any issues with this method given the depth of the void?

    The depth of the void is an advantage in many ways. It certainly means you could use EPS instead of PIR, saving some cash. The only thing you didn't mention is a narrow strip of insulation around the edge of the concrete & screed, and here something like PIR or phenolic would pay dividends (or even VIPs or aerogels if your pockets are deep).

    2) PIR insulation between joists

    The joists are only 50mm and most people suggest 100mm PIR. Could extra timbers be fixed to the joists at the counter batten points so allow for 100mm insulation?

    You could fix extra timbers underneath the joists to increase the depth of insulation. Or if you can get access from underneath, simply fasten 50-100 mm or so of insulation to the underside of the joists, thus covering the whole area.
    • CommentAuthortony
    • CommentTimeOct 14th 2018
     
    Fill the whole void with something insulating and non degradable, my choice would be platinum eps beads or if concrete eps sheets under a slab
    • CommentAuthorPetlyn
    • CommentTimeOct 15th 2018
     
    As per Tony's advice - an alternative to EPS is expanded glass bead insulation which doesn't degrade, decay or reduce in effectiveness, is inert and easily poured into small spaces. We have left-over material from our self-build and could send you a few to consider if this is of interest?
    • CommentAuthorItsBobbins
    • CommentTimeOct 15th 2018
     
    Thanks DJH and Tony. Food for thought.

    DHJ - are you suggesting i could fasten all of the boards to the underside of the joist? like this

    U U U U
    --------------------

    as i have around 50cm of space beneath the joist but no access hatch. I think it would be easier to batten then fit the insulation from above.


    Both - could the EPS beads present damp issues and would the beads be filled to finished floor level?


    Tony - given the choice would you go beads or slab?


    thanks again.
    • CommentAuthortony
    • CommentTimeOct 15th 2018
     
    Beads, I like the maximum amount of insulation
    • CommentAuthorbhommels
    • CommentTimeOct 16th 2018
     
    Option 1) it is for me. Next week our suspended wooden floor is going to get ripped out, the 370mm void filled up with EPS, and screeded over with UFH pipes embedded.

    I considered filling the void with beads, but I did not want to worry about dampness/humidity migration issues for the coming decades. There are a couple of joists that have become spongy due to condensation on a gas pipe entering the house, and probably also a dodgy soakaway. Addressing these means lifting the floorboards and replacing those joists anyway, so then we are halfway there already.
  1.  
    Sorry to resurrect this but i am finally getting to the point where i might be able to crack on.


    Can anyone give me any details on dealing with building control? How do i start the ball rolling and how expensive is it likely to get? My old man is able to help with the hardcore and generally with the ground works so materials shouldnt be a problem but the BCO stuff is putting me off.

    I'm wondering if it might be easier to go with the insulation between joists option. having had a proper look, i have 75mm joists. Would 75mm insulation be enough? I've read a few posts suggesting to not have insulation thicker than the joist itself. Is there any kind underlay to help with the bridging from the joists themselves?

    Still reluctant to go with the EPS beads option so i think i'd go for one of the other 2 options.

    cheers
    •  
      CommentAuthordjh
    • CommentTimeJan 7th 2019 edited
     
    You need to decide whether to use your local council building control service or a private firm. Whichever you choose, or more than one if you wish, the first thing to do is to phone them up and have a chat. Describe what you're going to do and ask them what will be involved from their point of view, and of course what it will cost. It will probably be helpful to have some drawings and ideally a specification to give them. You can also do it online if you prefer.

    Make your mind up which service to use, get them to confirm in writing what they are expecting you to do, and go from there.

    Costs are not standard - they are decided by each council or company. There are some example prices online, e.g. https://www.wigan.gov.uk/Resident/Planning-and-Building-Control/Building-control/Fees-and-payments.aspx that will give you an idea of the likely magnitude.

    edit: there's a guide to the process at https://www.labc.co.uk/homeowners/5-steps-building-regulations-approval?language_content_entity=en
    • CommentAuthorwellburn
    • CommentTimeJan 8th 2019
     
    you can do building control in 2 different ways. - both cost the same based on total project budget
    A building notice is easier. - you don't need drawings, you just pay and the inspector visits you, you discuss & agree what you are going to do, and they re-visit at end or during to check all being done correct.
    Might be a final isnpection visit.

    means you get benefit of their expertise, and all signed off.

    I am going down the lift boards anf infil with silver ESP boards. gonna rig a hot wire to cut to size.
    Will put VCM over before re fitting boards.
    undecided if i am going to hammer nails through before lifting or knock out after.
  2.  
    Do ESP boards help you see into the future?:bigsmile:
  3.  
    ''undecided if i am going to hammer nails through before lifting or knock out after.''

    If you have t & g boards and want to save them, you'll want to punch the nails through. I reckon to scrap less than 25% with this method. Although you might lose the odd bit of tongue, not enough to write them off.
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