under floorboard insulation

Discussion in 'Floors, Stairs and Lofts' started by hylas, 8 Nov 2010.

  1. hylas

    Joined:
    18 Sep 2010
    Messages:
    30
    Thanks Received:
    0
    Location:
    Cheshire
    Country:
    United Kingdom
    Hi all
    The cold coming from under our floors is terrible. its a 1930 house with approx 1ft under the joists at the most and air bricks everwhere
    looking at r values etc it would seem insulation between joists on netting would be far better than good underlay it a shame about having to take up the floor boards..
    The questions
    1. is what is the best type of insulation to use
    2. where to buy it from
    3. is b&q space blanket foil wrapped suitable
    thanks in advance
    phil
     
  2. JohnD

    Joined:
    15 Nov 2005
    Messages:
    38,250
    Thanks Received:
    1,522
    Location:
    Hampshire
    Country:
    United Kingdom
    that's why carpet became so popular
     
  3. hylas

    Joined:
    18 Sep 2010
    Messages:
    30
    Thanks Received:
    0
    Location:
    Cheshire
    Country:
    United Kingdom
    yep and its not cutting it

    come on now. when you get visitors comming round with the dog and it wont lay down cos its so cold and the misses has frozen feet its time to buy thicker socks or insulate
     
  4. JohnD

    Joined:
    15 Nov 2005
    Messages:
    38,250
    Thanks Received:
    1,522
    Location:
    Hampshire
    Country:
    United Kingdom
    sorry I got the idea you had taken the carpet up

    can you get under the floor? how much space have you got underneath? is it old square-edged boards, or T&G, or chipboard?

    is there a concrete oversite beneath the floor?

    have you got an open fireplace? is your ground floor open-plan, or do you leave the interior doors open? what sort of windows have got and are they draughty? have you got a conservatory opening off the living room? are you terrace/semi/detatched or what?

    how old is the house, and what is it built like?
     
  5. hylas

    Joined:
    18 Sep 2010
    Messages:
    30
    Thanks Received:
    0
    Location:
    Cheshire
    Country:
    United Kingdom
    1930 s detatched brick built house double glazed all around, talking about a single room 4m x 3m x 10 ft high 1 door 1 bay window gas fire no direct draughts. t & g floor boards on about 10" beams with 10-12 inches below, not sure if its soil or conc. down there but its dirty. air bricks all over outside hense the icelandic floor, gas central heating with gas fire backup. cavity wall insulation and 400mm loft insulation, good quality carpet with underlay less than 2 years old.

    thinking take up the floor boards, staple mesh to the underside of the beams as i go along and put 150 to 200mm of insulation blanket in, perhaps with insulation foam on the ends up to the wall, and tape the joints, just require some expert advise

    thanks
     
  6. Eh_Dinna_Ken

    Joined:
    29 Oct 2007
    Messages:
    11
    Thanks Received:
    0
    Location:
    Fife
    Country:
    United Kingdom
    Hi - you have the right idea however it does sound like a lot of work. I have the same issue in my house and will do all possible to insulate from the underside as lifting the floor is too much to consider at this point in time.

    Instead of wire mesh you might want to consider this:

    http://www.glidevale.com/protect_tf200_thermo.html

    Stapled to the underside of the joists. You would have to be carefull to get a good compression fit for the insulation so that the membrane was not exposed to excessive weight... which might lead you to choosing an insulation board rather than 'loft roll'. cut the boards to a tight fit and it should stay... I'd trust it anyway.

    A nice layer of this:

    http://www.glidevale.com/protect_vc_foil.html

    on the warm side of the floor would finish it off nicely. All joints and perimeter full taped/ sealed.

    You could set about nailing timber battens to the side of the lowest part of each floor joist, along the entire length of the joist, so as to form a 'stop' for the insulation board. This would be the ideal way to do it in my opinion, however cost and time and hassle come into it.

    Whatever happens you are faced with the impractical reality of having to somehow retain insulation under the floorboards. If there is sufficient space below the floor I would suggest doing all you can to avoid lifing all the floorboards - it may be possible to lift every 4th or 5th, perhaps 2 at a time. I did this for a first floor bathroom which was very very cold however obviously I had the plasterboard ceiling below to support the insulation.

    Would be very pleased to hear if anyone else has an idea of how to overcome this popular problem.
     
  7. ajrobb

    Joined:
    23 Jan 2010
    Messages:
    1,656
    Thanks Received:
    162
    Location:
    Sussex
    Country:
    United Kingdom
    Speaking as a novice:
    Normal to drape netting over top of joists and staple near insulation depth. There should be no gap between the insulation and the floorboards. No impermeable membrane as spills should be allowed to drain.
     
  8. hylas

    Joined:
    18 Sep 2010
    Messages:
    30
    Thanks Received:
    0
    Location:
    Cheshire
    Country:
    United Kingdom
    Hi the reason i thought of foil wrapped space blanket was due to the r value being around 4 were as insulation board would be around 2.5 also board is around 4 times the price per sq metre

    does the insulation have to be up to the undeside of the floor board? or can it have a gap?

    i thought at the wall ends i could put a piece of insualtion board at an angle, with space blanket between those two ends taped on to the boards supported by netting, so as not to block the air flow under the house but to seal the underside of the floor board from the cold but keeping the bottom edge of the beam open to air flow

    saw this netting advertised it looks good
    http://www.tenax.co.uk/showcategory.asp?category=166&menu=3
     
  9. ajrobb

    Joined:
    23 Jan 2010
    Messages:
    1,656
    Thanks Received:
    162
    Location:
    Sussex
    Country:
    United Kingdom
    I have been advised not to put an impermeable layer under the floor as this prevents spills from draining.
    I think so.
     
    • Thanks Thanks x 1
  10. hylas

    Joined:
    18 Sep 2010
    Messages:
    30
    Thanks Received:
    0
    Location:
    Cheshire
    Country:
    United Kingdom
    Hi ajrobb

    Cheers looking around the websites its good advice you've given there.

    what happens with the insulation against the wall? can it be pushed up to the wall or will the mineral wool / multi roll suck up moisture do i need a membrane or something
     
  11. ajrobb

    Joined:
    23 Jan 2010
    Messages:
    1,656
    Thanks Received:
    162
    Location:
    Sussex
    Country:
    United Kingdom
    The walls between the joists should all be above the DPC, so they ought to be dry. Condensation shouldn't be a problem with adequate sub floor ventilation. Any water pipes beneath the insulation must be protected by thick (bye-law) insulation.
     
  12. hylas

    Joined:
    18 Sep 2010
    Messages:
    30
    Thanks Received:
    0
    Location:
    Cheshire
    Country:
    United Kingdom
    For anyone thinking of insulating below the floorboards. i have just done it. it took 20 hrs and dam near killed me, getting the tongue and grooved floorboards up was terrible.

    unable to crawl below the joists stapling the netting was a real chore.

    stuffing in the insulation was easy.

    but the floor boards christ... after i finished it all i screwed them down when they are nailed down its a swine.. and im a joiner.

    ps insulated the garage roof from underneath, now that was easy.

    so to recap: if you can do it from below its quite easy but if you dont have enough access and have to work from above be prepared to work lke a dog and wish you had not started

    Merry Xmas
     
  13. mointainwalker

    Joined:
    24 Aug 2009
    Messages:
    2,145
    Thanks Received:
    201
    Country:
    United Kingdom
    Yes, but for a couple of days intensive work you're going to be a hell of a lot more confortable and make big savings on the heating-bill.........................and the dog can come and visit now :D
     
  14. hylas

    Joined:
    18 Sep 2010
    Messages:
    30
    Thanks Received:
    0
    Location:
    Cheshire
    Country:
    United Kingdom
    should anyone be interested this is where i got my netting from maybe not the cheapest or the best i have no idea however it is a place to start from.. http://www.tenax.co.uk/showcategory.asp?category=166&menu=3

    and i bought a stapler called tacwise from argos for 19.95 a dam sight cheaper than ebay

    Oh and if you look on homebase website the loft blankets are half price at 3.98 and are buy 1 get 1 free.. not suitable for under the floor but great for the garage
    happy shopping.....
    ps SHE now turns down the heating and says the room is warmer..RESULT !
     
  15. FD

    FD

    Joined:
    3 Jan 2011
    Messages:
    15
    Thanks Received:
    0
    Country:
    United Kingdom
    I've just done one room at my Dad's.
    I used a roll and a half £3 a roll glass fibre from one of the sheds, held it up with cores from a twin and earth screws and penny washers.
    I was going to use polyporpylenes string but thought best not in case of fire. Uhm like sagging insulation would be the biggest problem in a fire.
    Horrible job as there is only about 400mm under the floor but it's a lot warmer in there.
    Doubt I'll complete insulating under the whole house, as that was the deep end. There's far too much clutter to move and the floorboards are good 1920s timber
     

Share This Page