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.




  1.  
    Firstly thanks for all the useful discussions and info on here - I have learned tonnes simply reading the threads.

    I am putting a single storey, flat roof extension on my house (~5 x 10m).

    After much deliberation regarding the walls, I have opted for the approach I first saw detailed by Viking House - single leaf block wall with 150-200mm EPS on the outside. I will use conventional foundations and run the EPS below ground level. The thing is all the detailing I can find shows a render finish.

    I have seen posts by Fostertom (I think), explaining that you can hang the vertical studs (that I want to fix the timber cladding) off (thermally isolated) timbers fixed to my roof timbers.

    However I have a couple of extra questions -

    1. If the vertical stud 'hang' from the top, how to fix the bottom of the rail? I guess it must stop 200mm above ground level like the actual timber cladding?

    2. Would you have any fixing into the block? i.e. through the vertical timber, through the 200mm EPS into the block? If so how?

    3. How to 'finish' the ground (and below) EPS? Would marine ply be OK?

    4. What does the EPS 'sit' on? Do I just make the foundation wider so effectively 'build off' the concrete with the EPS?

    Sorry to ask. I really want to get this new bit of the house performing (from an energy perspective) well. I will eventually retrofit the existing house with similar principles (such as filling the floor void with EPS bead! - what an idea).

    Thanks.

    Phil
  2.  
    Hi Phil, I would think really carefully before doing what you want to do. It would be quicker and easier in every way to make your extension timber frame and forget blockwork. The only time it really makes sense in a new build to do block and EWI is if you are going to render the outside - stick the insulation to the block, stick the render to the insulation, no expensive fixings, no bridging.

    I'm sure you can hang your whole timber cladding from the roof timbers but you are going way out of the norm there and will need to calculate the forces involved. Trying to get structural fixings through to hold the timber cladding onto the blockwork gets expensive fixings wise.

    You can either render the EPS below DPC or use something like a uPVC fascia board.
  3.  
    Thanks for the input Willie.

    Perhaps I should rethink my approach - either block + render, or timber frame + cladding.

    I was leaning towards cladding as with 3 children all under 5, the walls on the back of the house are in for some years of abuse yet! Not sure such a thin layer of render over EPS would withstand it.

    Cheers,

    Phil
  4.  
    Posted By: Philbobagginsiii
    I was leaning towards cladding as with 3 children all under 5, the walls on the back of the house are in for some years of abuse yet! Not sure such a thin layer of render over EPS would withstand it.


    Hi Phil,

    All the local new build schools have thin coat renders, there is a fibreglass reinforcing mesh embedded which spreads impact loads, it is quite tough, ask a few suppliers for a sample board and try and destroy it yourself! The other thing with your extension is that it is a quite a long wall and you may need to think about support piers for the blockwork or windposts which complicate matters a bit, depends on the loads and how it is divided internally.
    •  
      CommentAuthordjh
    • CommentTimeMay 12th 2015
     
    Even if you hang the battens from the roof you will need to secure them at the bottom, and probably middle, to stop them bowing and/or getting blown about by the wind.

    At the base of the wall, we simply stood some paving slabs in front of the EPS (council slabs - D50). They're held in place by the backfill over their lower part. Our cladding battens rest on the tops of those.
    • CommentAuthorwookey
    • CommentTimeMay 12th 2015
     
    If you did go for battens in the EPS, I'd sink horzontal members 50x100 (3off?)? into the EPS (routed channel) and glue them (with a few through-fixings, as low-conductivity as you can manage). This can be quite strong. You need to search out the right glue for polystyrene, but probably whatever it's being stuck to the wall with will be good.

    That should give almost no bridging but still be strong enough to hold the cladding in. As willie says, this is unconventional so some sums to check that it'll stay on in a high wind would be in order.

    I've used quite a lot of battens-glued-into-PUR and it works well.
    • CommentAuthorbarney
    • CommentTimeMay 12th 2015
     
    How about a medium dense block inner wall, a stub wall external up to DPC/bottom of cladding and use a larsen truss stuffed with insulation. Roof load taken on inner block structure

    Regards

    Barney
    •  
      CommentAuthordjh
    • CommentTimeMay 12th 2015
     
    Posted By: wookeyIf you did go for battens in the EPS, I'd sink horzontal members 50x100 (3off?)? into the EPS (routed channel) and glue them (with a few through-fixings, as low-conductivity as you can manage). This can be quite strong.

    That sounds like an awful lot of work and massive overkill, but perhaps we're thinking of different scenarios?

    In my case it was single storey cladding, supported top and bottom with an odd middle screw through to stop bowing. The battens were just regular 2x1 tile battens and definitely don't want to be embedded in the EPS because they make the ventilated drainage space, in conjunction with a membrane behind them. The battens only have to support timber cladding, which certainly in the case of our cedar featheredge isn't that heavy.
  5.  
    Thanks for the input here. I really appreciate it.

    djh - so you just fixed through the EPS into the block, top and bottom of the battens? With the odd middle screw? I guess sitting the battens on the slabs as you said further up the chain really helps here. How thick was the EPS? What fixings did you use?

    I must admit, I am leaning towards Willie's suggestions further up and might ditch the timber cladding for a modern render system. I'd actually forgotten a good mate of mine has used a Wetherby system on a number of jobs. I prefer the appearance of timber, however my main objectives are achieving 200mm EPS with the walls and as easy a life as possible (in terms of construction and the wife!).
  6.  
    Its a question of taste and aesthetics but you could do a mix and match. Do the majority in rendered EPS, and have sections of wall in timber cladding as an architectural feature. Top half of a wall on one of the facades for example. Or the garage in timber cladding.
      51_boulevard_de_la_republique_a_porcheville_copie__082953000_1133_08032013.jpg
    •  
      CommentAuthordjh
    • CommentTimeMay 13th 2015
     
    Posted By: Philbobagginsiiidjh - so you just fixed through the EPS into the block, top and bottom of the battens? With the odd middle screw? I guess sitting the battens on the slabs as you said further up the chain really helps here. How thick was the EPS? What fixings did you use?

    Ours was a bit of timber frame, not blockwork. We fixed the top of the battens to the roof structure above the insulation, and stood them on the edges of the upright paving slabs at the bottom. Then we put some screws through the EPS to the timber frame at the bottom and in the middle until it felt stable. It's only a sun room outside the thermal envelope so I wasn't paranoid about thermal bridging. I planned to use stainless screws but I seem to remember we ended up with 150 mm plasterboard screws (the EPS is 100 mm thick).
    •  
      CommentAuthorfostertom
    • CommentTimeMay 13th 2015 edited
     
    Suspending vertical cladding rails (say 35x50, not 'studs') from rafter ends is no big deal, hardly needing Engineer input. This is only necessary if they are well outboard from solid wall (whether block or stud) e.g. outboard of thick EWI, which would put enormous cantilever forces onto horizontal rail-fixing screws (through the EWI). You couldn't rely on friction to take the cantilever i.e. don't think that 'clamping' the rails to the EWI through to the solid wall, would prevent it all sliding downward.

    However, those same horizontal rail-fixing screws (through the EWI) will happily take any horizontal force i.e. prevent the cladding rails from bowing or drifting away from contact with the EWI. You'd need such screws @ perhaps 600c/cs, not just 'top and bottom'.
  7.  
    Thanks again to everyone for the all extra input here. Coupled with the other relevant threads on the forum I feel well informed on the latest project.

    Phil
    • CommentAuthoran02ew
    • CommentTimeMay 18th 2015
     
    hi philbo
    have you thought about using 300mm ibeams well fixed to external of blockwork @ 800C, then cladded with timbervent and filled with bonded thermal bead(super) then counterbatten and covered with whatever cladding.

    This is a system we developed and used recently on a new build in Gloucester, the heal of the steico(ibeam) rested on the edge of the founds creating a very strong ground for hanging heavy external cladding also because the ibeams are well fixed(designed by SE) to the block skin it solves the slenderness ratio of 100mm/140mm single skin walls foundation XPS rises up to block of bottom of ibeam cassette to create a tight space for injection bonded bead.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 19th 2015 edited
     
    That's impressive Andy, when you add in solving the slenderness of 100/140 blockwork.

    It ticks the box of enabling footprint/excavation at found level to be minimal (compared to having to support a wide-cavity outer skin as well as the 'inner' skin).
    But it does make a wall that's thicker (427 or 467) than using a stud 'inner' skin (315) because all the insulation thickness (the I-beam zone) has to be outboard of the blockwork 'inner' skin instead of filling its thickness with insulation if it were a stud 'inner' skin. That could be a killer on a v tight site.

    I suppose you do the rafter slopes with I-beams bead-filled as well?
    •  
      CommentAuthordjh
    • CommentTimeMay 19th 2015 edited
     
    Posted By: fostertomBut it does make a wall that's thicker (427 or 467) than using a stud 'inner' skin (315)

    What does the block wall or inner studs do? Surely the I-beams would stand up by themselves?
  8.  
    <blockquote><cite>Posted By: djh</cite><blockquote><cite>Posted By: fostertom</cite>But it does make a wall that's thicker (427 or 467) than using a stud 'inner' skin (315)</blockquote>
    What does the block wall or inner studs do? Surely the I-beams would stand up by themselves?</blockquote>

    thermal mass
    •  
      CommentAuthorfostertom
    • CommentTimeMay 19th 2015
     
    Andy,

    Q1: leaving aside the bonus of enabling blockwork thinner than 190 Regs deemed-to-satisfy, do you find that
    a) 300 I-beams fixed and timbervent boarded, and blowing full of 300 of EPS bead
    is cheaper than
    b) 300 (aged?) EPS board fixed as EWI, foamed between?

    Q2: do you find that
    c) 100 blockwork wet plastered; then 300 I-beams fixed and timbervent boarded, and blowing full of 300 of EPS bead
    is cheaper than
    d) 89 CLS studwork plasterboarded and OSB'd, blown full of 89 of EPS bead; then 200 (aged?) EPS board fixed as EWI, foamed between?
    •  
      CommentAuthordjh
    • CommentTimeMay 20th 2015
     
    Posted By: bot de paille
    Posted By: djh
    Posted By: fostertomBut it does make a wall that's thicker (427 or 467) than using a stud 'inner' skin (315)

    What does the block wall or inner studs do? Surely the I-beams would stand up by themselves?


    thermal mass

    I can see that for the blocks but not for the studs. In the case of the blocks, we then get into the whole discussion about whether thermal mass is worthwile and if so how much :confused:

    (FWIW, I do believe in [some] thermal mass)
    •  
      CommentAuthorfostertom
    • CommentTimeMay 20th 2015 edited
     
    Posted By: djhWhat does the block wall or inner studs do? Surely the I-beams would stand up by themselves?
    If that's the inner studs that I introduced into the discussion, that was alternative to using I-beams - i.e. studwork clad with EWI instead of blockwork plus I-beams.

    If the blockwork is for thermal mass, then Andy's 100 is all that's needed, and confers the max thermal mass that's possible - any greater thickness (like deemed-to-satisfy 190) adds no effective or active thermal mass, because on the diurnal-cycle basis of solar coming in thro windows daytime then leaving again at night, the temperature waves only have time to penetrate the inside 100 or so of blockwork before the heat flow reverses again.

    Only if deliberate measures are taken to activate greater thicknesses, is greater thickness worthwhile!

    Having said all that, the ground floor slab (and/or activated subsoil block) can provide all the thermal mass that's beneficial, so an all-stud superstructure is fine.
    • CommentAuthoran02ew
    • CommentTimeMay 21st 2015
     
    Tom

    Q1 never tried B but would think you couldn't get twist fixes to work properly, accurately or easily at that length. Plus I'm happier that eps blown into cassette is better and quicker than struggling with sheets at that width of sheet around scaffolds and awkward cuts. Connection with roof insulation is very neat weather roof is solid sheet or blown.

    Q2 I think we would struggle with B as 89mm wold be too thin. Plus not happy with pb as internal cassette wall any more but would recommend second OSB And service void.
    However the gain with opt A is he thermal mass. Single skin walls are quick to build lintels are simple and the job move on very quickly. No weather concerns and faffing keeping OSB dry.
    • CommentAuthoran02ew
    • CommentTimeMay 21st 2015
     
    Tom
    In answer to you first Qs
    Walls are a bit thicker but you gain thermal mass. Plus not sure you could or would want to build two storey with only 89mm of stud. Our current job uses 145 studs over two storeys and SE spec was triples and quads at stress and load points. Which is costly and time Consuming.
    I do like to use I beams for roofs and would always fill with injected bonded thermal bead.
    • CommentAuthoran02ew
    • CommentTimeMay 21st 2015
     
    Also worthy mentioning that in flood areas labc frown on timber frame construction so the block inner and I beam outer works better. We incorporated a 900mm plinth of e board and then timber vent above that.
    •  
      CommentAuthorfostertom
    • CommentTimeMay 21st 2015
     
    Gd thoughts
    • CommentAuthorborpin
    • CommentTimeMay 21st 2015
     
    Posted By: an02ewhave you thought about using 300mm ibeams well fixed to external of blockwork @ 800C, then cladded with timbervent and filled with bonded thermal bead(super) then counterbatten and covered with whatever cladding.
    Is there a condensation risk on the web of the ibeam?
    • CommentAuthoran02ew
    • CommentTimeMay 21st 2015
     
    how? i cant see why condensation would form within the insulation zone on a timber web? but maybe its one for Tom
    •  
      CommentAuthorfostertom
    • CommentTimeMay 21st 2015
     
    Hmmmm, sleep on it
Add your comments

    Username Password
  • Format comments as
 
   
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   
Logout    

© Green Building Press