Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)

Categories



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.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.
Buy individually or both books together. Delivery is free!


powered by Surfing Waves




Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
 Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.

The AECB accepts no responsibility or liability for any errors or omissions in the content of this site. Views given in posts are not necessarily the views of the AECB.



Housing - New Build: Wall Build-up for timber frame structure validation

Bottom of Page

31 to 45 of 45

  1. <
  2. 1
  3. 2
  4. >
    • CommentAuthorOj0001
    • CommentTimeAug 27th 2026
     
    That has all made for very interesting reading, thank you!

    How nice it would be to have access to WUFI software to validate different build ups, for all its drawbacks and pessimism, the Glaser Method is very easy to play around with. I don't suppose anybody knows of a UK service that's reasonable for validating a construction?

    The more I look at the details I find the idea of moving the OSB to the internal face, keeping it warm and promoting outwards breathability appealing. The only concern I have using EPS or Rockwall EWI in this configuration, is that it wouldn't have full support across the back, but only on studs. Does anybody have experience with this configuration?
    •  
      CommentAuthorfostertom
    • CommentTimeAug 27th 2026 edited
     
    The point of putting the OSB3 vapour-breatheable but airtight sheathing/racking, all edges supported, gapfilling glued and screwed/power nailed, on the outside of the studs, rather inside as is universal timber framing practice, is that in that location it's uninterrupted by joist ends, partitions, service holes etc, all of which have to be carefully sealed around with expensive sticky tapes, which professional airtightness testers know are rarely done perfectly and may start parting within as little as six months. Avoid all that by putting the OSB3 on the outside face of the studwork i.e. in the middle of the insulation sandwich - it's then stupidly easy, foolproof to do by ordinary chippies (see pic). With plasterboard direct on the inside face of the studs (which is OK to puncture for services, so no service void required) and OSB3 on the outside, no problem with restraining the insulation between the studs.
      2011-07-26 021reduced.jpg
    •  
      CommentAuthorfostertom
    • CommentTimeAug 27th 2026 edited
     
    Inside view of studwork, minimised because sheathed with OSB3 as racking membrane - almost a stressed-skin monocoque, and showing use of 0.7mm galv steel dryliner's straps to support board edges by self-tapping screws, rather than cut n fit timber noggings.
      2011-07-26 040reduced.jpg
    • CommentAuthorMike1
    • CommentTimeAug 27th 2026 edited
     
    In addition to the above, once built you want to avoid vinyl paints, which would block the vapour permeability of the structure, which could lead to problems. That is, choose a paint with an sd-value <= 0.5 m. If you search for something like 'breathable paint' there are plenty of them out there these days.
    •  
      CommentAuthorfostertom
    • CommentTimeAug 27th 2026 edited
     
    That's right. For ever!
    • CommentAuthorborpin
    • CommentTime5 days ago edited
     
    In my head (for the house I'll probably never build), I have been toying with a double 90mm CLS stud approach. Outside sealed much as Tom has, but a second stud inside with the studs offset where possible. This inner studd carries the floor above, window openings etc (so reduce cold bridging) and also allows room for european style roller shutters.

    It would be a flat roof, cladding of some sort and metal web joists. Probably try to use wool. I used Icyene last time and really liked it for gap sealing. Seen too much about Warmcel slumping to trust it. I'd avoid insulation outside the OSB if I could (might need a bigger internal buildup). I worru about rodent damage to external insulation.
    Posted By: Mike1once built you want to avoid vinyl paints
    That's an interesting thought.
    •  
      CommentAuthorfostertom
    • CommentTime5 days ago edited
     
    Say more about why double studs - why not just the inner set of studs? Not sure how roller shutters affects it.

    Insulation outside the OSB is what puts it (and any timber) into the non-condensation zone. Without approx half of the insulation outboard, the OSB is right in the outboard condensation zone.

    That's my concern also about timber I-studs, sheathed inside and out and blown full of Warmcel or similar - the outer sheathing and outer 'flange' of the I-joist are right in the condensation zone. But that approach is popular and successful, it seems, so such intermittent condensation may not be problematic. As long as it is intermittent and the re-drying potential is excellent incl I'd a thought a very well-ventilated cladding cavity (which isn't necessary in my scheme).
    •  
      CommentAuthordjh
    • CommentTime5 days ago edited
     
    Posted By: fostertomSay more about why double studs
    Sounds like a Larsen truss, without the connecting panels between the studs :bigsmile:
  9.  
    Breathable paint - make sure to budget enough for it!

    Just paid nearly £100 for a 5 litre tin of clay based paint, that covered 20m2
    •  
      CommentAuthorfostertom
    • CommentTime5 days ago
     
    Actually, I hear that standard paints are quite permeable? True? But multiple re-coats over a lifetime?

    Posted By: djhSounds like a Larsen truss, without the ...
    Yes, that's what it's called, that I was describing, and questioning.
  11.  
    Afaics most of the info online is posted by people who sell clay paint or similar! Have you seen different?

    The consensus seems to be that vinyl matt or acrylic matt are breathable enough that you cannot rely on them as a VCL, but yet not breathable enough that you can use them in a wood-fibre/lime type of highly breathable construction.

    Being water based, they must have enough permeability to allow the water base to dry out. The manufacturers seem very reluctant to share SD values on the data sheets which suggests they're not good.


    This leaves me in a dilemma - having spent a lot of time and cash on breathable insulation I'm not risking spoiling it with a non breathable paint - but it would be nice if something else were available a bit cheaper and with certified SD values!
    •  
      CommentAuthorfostertom
    • CommentTime5 days ago
     
    That's clarifying - thanks Will.
    •  
      CommentAuthordjh
    • CommentTime4 days ago
     
    Posted By: fostertomActually, I hear that standard paints are quite permeable? True?
    When I built, the only one that published an Sd value was Dulux Trade Supermatt so I used that as an undercoat on all the internal walls. I used Earthborn clay paint as an undercaoat on the lime plaster and as a finish coat everywhere. I haven't found an Sd value for the Dulux paint in a quick search today.
    • CommentAuthorMike1
    • CommentTime4 days ago edited
     
    Posted By: WillInAberdeenBeing water based, they must have enough permeability to allow the water base to dry out. The manufacturers seem very reluctant to share SD values on the data sheets which suggests they're not good.
    Watching paint dry: https://www.painternearme.com/color-insights-trends/understanding-science-behind-curing-process

    Posted By: WillInAberdeenJust paid nearly £100 for a 5 litre tin of clay based paint, that covered 20m2
    That's quite steep. Here in France the prices range from €12.50 (off-white) to €16 per litre, if you buy it in 10L tubs (so £110 to £140 for 10 litres), which is a little more reasonable.

    It probably seems worse as regular paints are really cheap in the UK, compared to here. For example B&Q are selling 10 litres of white Dulux Matt for £28; here it will set you back £43 (€55). So I pay around 2 x more for clay, you're paying nearly 4 x more.

    There must be some DIY recipes online...
  15.  
    So optimal build up appears to be:

    PB
    150mm studs infilled as necessary
    11mm OSB
    100mm EPS
    Thin coat render

    What if it was masonry?

    PB foam fixed
    block on flat
    150mm EPS
    Thin coat render

    Sound about right?

31 to 45 of 45

  1. <
  2. 1
  3. 2
  4. >
Add your comments

    Username Password
  • Format comments as
 
Back to Discussions Top of Page
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press