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Best way to Insulate 9inch solid wall

Discussion in 'Plastering and Rendering' started by Chunkytfg, 13 Dec 2018.

  1. Chunkytfg

    Chunkytfg

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    I'm new so please be kind!

    New house purchase is immanent and planning of the massive list of work to be is being compiled.

    One of the first issues is trying to get the place warm and free from damp/condensation by insulating the external walls. And here comes the questions.

    Best way to insulate? I've been doing my research and it seems there are a few ways to do it.

    External insulation would be nice but so expensive it isn't going to happen so Internal insulation with a slight loss of room size it is!

    So how to do it. So far i've seen/read 3 ways of doing it.

    1-Foil backed insulation direct to the wall with batons fixed to it and plasterboard over it.

    2-Small batons direct to the wall or on small plastic pillars to keep the baton off the wall and therefore damp, to create an airway then Insulation backed plasterboard direct to that.

    3-Large batons again kept off the wall with a plastic spacer with insulation mounted between the batons but held off the wall somehow with the plasterboard mounted to the batons on top.

    Does that seems about right?

    2 and 3 to me seem basically the same with 2 being quicker, simpler and probably more expensive.

    Also my understanding is the moisture/damp comes from the war air hitting the cold walls so you need to seal it somehow. Expanding foam in all the joins and then foil tape on the joins. How would you do this if you used Insulated boards as the only surface to tape is the plasterboard itself.

    The house has a gap under the floorboards with air bricks round the floor to allow air movement under the floor. So do I make sure that the air can vent from the space under the floor to the gap I create behind the boards assuming I pick 2 or 3? Maybe split the floorboard down that edge to allow ventilation?

    Annoyingly every single external wall in the house except 2 very small sections in the bathroom and 3rd bedroom has a window on it. How do I finish round the window? I haven't got room to insulate to the same thickness as it'll cover a large section of the window so can i do the same with batons etc but using a much thinner level of insulation?

    If you made it this far then thank you.

    Oh and hello. This forum looks like it could be a very suitable source of info in the future!
     
  2. Bonni

    Bonni

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    You could dot and dab insulated boards to the walls and use plasterboard fixing foam and foam gun.

    Window reveals don't normal get done because you haven't got the distance between the reveal and glass.
     
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  3. Notch7

    Notch7

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    I would say thats the best method.

    Highest u value bang for your buck since there are no cold bridges. And the battens form a service void, ideal for cables.

    You could chip plaster off reveals then fit insulated plasterboard if theres room. If not you could remove plaster from reveals and plasterboard.

    You will need new window boards.
     
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  4. JobAndKnock

    JobAndKnock

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    Having used it a few times now I think I'd rather go with Gypliner - faster and cheaper to install than timber battening and easier to get a straight, plumb wall surface. The trapped air between the wall and the plasterboard give you a service void and the trapped air acts as insulation. Worth taking a look at
     
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  5. foxhole

    foxhole

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    Gets my vote, did all my extension like that.
     
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  6. oldbutnotdead

    oldbutnotdead

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    The only disadvantage of dotting and dabbing insulation to the wall then glueing plasterboard to insulation is if you want to fix anything heavy to the wall - radiators are a standard feature, shelves could be a trial as well.
     
  7. wwwebber

    wwwebber

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    Yep dot and dab. Done that in my last house. Used plasterboard that was backed with 50mm insulation. Great result.
     
  8. motorbiking

    motorbiking

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    /\ This.

    Avoid Timber battens, they just reduce the insulation efficiency. If your plaster is blown and you are considering upgrading services (e.g. network, electrics etc) then take the plaster back to the brick wall and either use fixing foam or mechanically fix to the walls and then tape the joints and skim. By the time you've taken the old plaster off, Celotex PL4050 insulated plasterboard wont reduce the room size by more than a few cm.

    Note its cheaper to by plaster board and standard celotex sheets, but more labour needed. This will reduce the U value by at least 75%.
     
    Last edited: 20 Dec 2018
  9. cwhaley

    cwhaley

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    My house is also solid brick and despite the strong smell of bleach in the front bedroom, there was no real evidence of mold/condensation on the walls until 1 week after we moved in. I removed plaster to brick, battened the wall out, filled with 25mm Celotex, 25mm more Celotex over that (using foil tape), then plasterboard over that and the walls have been warm and mold-free since.

    Doing the bay window and external wall cost me about £70 all in. I was lucky as wickes sent 4 sheets to my house instead of 2 for some reason so I had plenty to use.
     
  10. MeldrewsMate

    MeldrewsMate

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    I've just read the Wiki page relating to old houses and damp/condensation. www.heritage-house.org seems to strongly object to insulating solid walls. I don't have any expertese in this field, but as I was about to ask a similar question here, I read that first.
     
  11. motorbiking

    motorbiking

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    I don't think they are talking about 1920s houses with Flemish/English bond solid walls.
     
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