Insulating Single Skin Outbuilding

Discussion in 'Builders' Talk' started by matt10matt, Dec 20, 2017.


Best method of insulating Block Wall



    0 vote(s)
  1. matt10matt

    matt10matt New Member

    Hi Hoping people could offer some advice PLEASE!!

    Started to convert a Single Skin (Concrete Block) Garage / Workshop in to a Mancave :)

    I have searched many a website trying to find the 'Best Method' and have eventually decided to purchase 25mm Celotex for the Walls along with 50mm Rockwool Soundslab. I made my mind up and was going for Option 1 below but have had some conflicting advice regarding installation and would appreciate it if any Builders out there could give me their professional opinion on the proposed options below:

    Option 1) Install the 25mm Celotex to the Block Wall with 3x2 battens holding in place spaced at 600mm Centres with the 50mm Rockwool in between then Plasterboard over battens.

    Option 2) Install Battens 3x2 against Block Wall again spaced at 600mm Centres with Rockwool in between. 25mm Celotex over battens and then Plasterboard over Celotex.

    Option 3) Any ideas welcome..

    NB. In both cases the Celotex will be taped with the appropriate Foil Tape and the Celotex will be used at the VCL.

    My Concerns / questions are :
    1) The Block work is porous and with the heavy rain the Water penetrates the brick work - With option 2 the Wool will become damp which will be a problem. I will eventually Render the Block Work so should that prevent the Water entering the inside of the building? I'm thinking I could seal the brickwork for the time being until such a time as I get the Rendering done?

    2) When the Block Wall is eventually Rendered will that cause any issues with moisture not being able to escape through the brickwork naturally if I went for Option 2? Moisture shouldn't get past the Celotex VCL so am I worrying too much about this?

    3) Should I use Tanalized Timber in the Wall?

    Any advice would be appreciated Cheers
  2. KIAB

    KIAB Super Member

    Give the wall a coat or two of Synthaprufe or similar to waterproof the walls.

    Has floor got a dpm?
    matt10matt likes this.
  3. matt10matt

    matt10matt New Member

    Thanks KIAB - As mentioned might do that until I get it Rendered as long as doesn't impact the bonding to the blockwork..

    Floor does have dpm at the moment - Will be putting DPM on top of existing concrete then Float 50mm Celotex as the floor..
  4. KIAB

    KIAB Super Member

    I meant inside walls, lost a word in my post.:oops:
  5. matt10matt

    matt10matt New Member

    No problem :cool:-

    Presume 'Synthaprufe ' is like a tanking solution? Would an alternative be to use DPM the walls along with floor joining if necessary with Waterproof joining tape?
  6. KIAB

    KIAB Super Member

    I use to paint wall & also a strip on floor ,usually just bit wider than the stud work/ bearers & board used, so no need for joining tape.
  7. matt10matt

    matt10matt New Member

    Just thinking painting walls will take forever to coat therefore didnt know if using DPM over wall was an option? How easy does Synthaprufe apply?
  8. KIAB

    KIAB Super Member

    Fairly easy with a long bristle brush, I tend to use Cementone Aquaprufe Damp Proofer from competitor, cheaper & just as good.
  9. matt10matt

    matt10matt New Member

    Thanks KIAB..
  10. I'd go with KIAB's suggestion too, if I were doing this again.

    The difference betwixt applying a 'paintable' DPM/slurry and simply tacking a sheet to the wall is that the former should stop any water actually getting through that wall. If you simply apply a DPM under the battens, you'll never know how much water could be 'pooling' there.

    Do it proper.

    Perhaps even apply both :)
    KIAB likes this.
  11. matt10matt

    matt10matt New Member

    After ALOT of deliberation I'm thinking of using the following method:

    i) Block Wall painted (Internally) with Liquid DPM to stop the water penetration - Outside will eventually be rendered too.
    ii) Fix tanalised battens to the wall (spaced at 600mm Centres) with the 50mm Rockwool between.
    iii) 25mm Foil back Celotex on top to ensure no thermal bridging through timbers, foil taped on joins and at edges to ensure continuous VCL.
    iv) 12.5mm Soundbloc Plasterboard skimmed

    Does anyone see any issues with this?

    My only real concern at the moment is there not being an air gap between the DPM on the wall and the Rockwool..

    Thanks in advance..

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