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Tying in External Wall Insulation on existing house to new extension

  • 15-04-2013 6:38pm
    #1
    Linto
    Registered Users, Registered Users 2 Posts: 171 ✭✭


    Hi,
    We are externally insulating our house which was built in 9" cavity block. We were going to build a cavity wall to the latest regs for the new extension but then we're not sure how to tie that into the existing house given we are going to externally insulate the walls.
    Question is: should we consider building the new extension in 9" cavity block and then externally insulate the whole house (existing and new). That way there is no "step" in the walls, internally or externally. Its also a good u-value on the walls - right?

    Any advice?
    Tagged:


Comments

  • #2
    harry21
    Registered Users, Registered Users 2 Posts: 519 ✭✭✭harry21


    It might not be possible to have both the inner and outer faces flush to the existing. But this situation would only arise if you were extending from the corner.... are you?


  • #3
    Linto
    Registered Users, Registered Users 2 Posts: 171 ✭✭Linto


    harry21 wrote: »
    It might not be possible to have both the inner and outer faces flush to the existing. But this situation would only arise if you were extending from the corner.... are you?

    Its a 2 meter extension all across the back of the house and a small extension to the front.
    Would building new wall with same 9" cavity block as existing be an option?


  • #4
    MicktheMan
    Registered Users, Registered Users 2 Posts: 2,880 ✭✭✭MicktheMan


    Linto wrote: »
    Question is: should we consider building the new extension in 9" cavity block and then externally insulate the whole house (existing and new). That way there is no "step" in the walls, internally or externally. Its also a good u-value on the walls - right?

    Any advice?

    I would do it with 9" block on flat and externally insulate.
    Make sure you seal the existing cavity block wall at the top to prevent warm air escaping out the top of the wall negating somewhat the ewi effectiveness.


  • #5
    Linto
    Registered Users, Registered Users 2 Posts: 171 ✭✭Linto


    Micktheman, is this the norm in these situations? Building with 9" cavity block seems to be somewhat frowned upon..?


  • #6
    MicktheMan
    Registered Users, Registered Users 2 Posts: 2,880 ✭✭✭MicktheMan


    I didn't mean 9" cavity block but rather standard 4" block (on flat)


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  • #7
    Linto
    Registered Users, Registered Users 2 Posts: 171 ✭✭Linto


    MicktheMan wrote: »
    I didn't mean 9" cavity block but rather standard 4" block (on flat)

    Buy existing house is 9" cavity block. How else will we seemlesssly tie in EWI into extension if we don't use the same??


  • #8
    MicktheMan
    Registered Users, Registered Users 2 Posts: 2,880 ✭✭✭MicktheMan


    Linto wrote: »
    Buy existing house is 9" cavity block. How else will we seemlesssly tie in EWI into extension if we don't use the same??
    4" block on the flat is same size (thickness) as 9" hollow block


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