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    • CommentAuthorTullich
    • CommentTimeMar 13th 2017
     
    Hi all,

    A quick first post to say hello.

    I'm shortly to undertake a timber framed self build in the Highlands, and have been reading posts here for a while now.

    I've finally got round to registering, and look forward to hearing your advice and suggestions.
    •  
      CommentAuthordjh
    • CommentTimeMar 13th 2017
     
    Hello and welcome. There are several people here based in Scotland, so you should get good advice (even if you leave the UK!).

    To get you in the mood for what I'm sure will be many more questions: How much of the build are you planning to do yourself? Have you chosen the timber frame supplier yet? What standard are you aiming at, in terms of insulation and airtightness?
    • CommentAuthorTullich
    • CommentTimeMar 13th 2017
     
    Hi djh - ha, that made me chuckle!

    Self build in this case means just that due to a super tight budget, and as such i'll be aiming to do the vast majority of the work myself, excluding electricals, stove install, etc. I'm not anticipating it'll be up quickly, so priority one is to get the roof on and walls sheathed in something that can withstand the weather.

    In terms of a TF supplier, that would be me then! I've been thinking on various wall types but have come back round to stick timber and mineral wool in light of the above.

    I'm not sure if there's a bona fide standard of insulation and air tightness that i'm aiming for - so, 'decent' and 'reasonable' should do for now!

    Something simple along the lines of:

    Horizontal Larch cladding
    Vertical batten
    Bitroc
    195mm frame with Rockwool flexi infill
    50mm cross frame with Rockwool flexi
    OSB and tape
    50mm service cavity with Rockwool flexi
    Plasterboard

    I'd happily change up some of the timber sizes to make things lighter to handle, but wonder about the often quoted 80/20 rule in terms of insulation in and outboard of the OSB?


    Any thoughts?
    • CommentAuthorEd Davies
    • CommentTimeMar 14th 2017
     
    Hi Tullich, where are you (approx) in Highlands? I'm in Caithness on the coast just south of Wick. Others on here tend to be around Skye.

    Somebody got in touch with me the other day who's planning an off-grid renovation the other side of Wick. He's bought a property there but is still in the south of England for the moment. I've pointed him at this forum.

    What sort of size house are you talking about? Number of storeys? 1.5? Do you have the land? Planning permission? Any particular planning constraints? I take it, given the tentative nature of your design that you've not got a building warrant yet. Any thoughts on the floor?
    • CommentAuthorskyewright
    • CommentTimeMar 14th 2017
     
    ...and if you are thinking of a small build, have you considered the 'let's call it a mobile home' route, which can take it outside of the realm of Building Control.

    I know of a couple of places on Skye that have done that. There may be more? Both the ones I know were built to be let as self catering accommodation, but both would be just fine for full-time occupation. One was built from a kit obtained from one of the Baltic states, the other was a DIY design and was 'stick built'.

    N.B. Such a design doesn't have to be,or look like, what you might think of as a caravan or mobile home (both the examples I know just look like small homes). Here's a link to the Highland Council's policy note "BST 018 Caravans and Mobile Homes", which defines what's needed to comply.

    http://www.highland.gov.uk/downloads/file/1346/bst_018_caravans_and_mobile_homes

    Just a thought.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 14th 2017
     
    Hi Tullich

    195 + 50 Rockwool promises to be a high insulation standard - full PassiveHouse would be within reach.

    Self-build - does that literally mean yourself, solo, for building the shell? Then yes smaller timber sections would be easier, and unfortunately, without craneage would rule out prefabricating panels on the ground - so much easier than in situ.

    http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=14944&page=2#Item_21 currently has suggestions about stick-build techniques eliminating layers and using more basic materials. Your proposed buildup doesn't seem to offer interim watertightness (before finish cladding) any more than the ideas illustrated in that link.
    • CommentAuthorringi
    • CommentTimeMar 14th 2017
     
    Posted By: fostertom195 + 50 Rockwool promises to be a high insulation standard - full PassiveHouse would be within reach.


    Maybe not on a small home, as PassiveHouse looks at the heating needed per m^2, but most people care about the total cost of heating there home. PassiveHouse can make a larger home with a higher heating cost look better!

    However the PassiveHouse process is very good even if you don't reach there required numbers to get the bit of paper.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 14th 2017
     
    Posted By: ringi
    Posted By: fostertom195 + 50 Rockwool promises to be a high insulation standard - full PassiveHouse would be within reach.


    Maybe not on a small home
    We don't know yet whether it's small or big, but anyway I said 'within reach' i.e. prob thicker but not that much more work/cost.
    • CommentAuthorTullich
    • CommentTimeMar 14th 2017
     
    Just home from work, and have had a quick look at this thread - thanks all for your interest.

    I've got some Daddy duties to perform, and will be back on here later.

    More info to follow.
    • CommentAuthorTullich
    • CommentTimeMar 15th 2017
     
    @Ed Davies: I'm on the East coast near Bonar Bridge, though work occasionally up in your neck of the woods. What I'm proposing is 1.5 height, double pitched roof, with a ground floor area of 70m squared and a further 50m squared as room in the roof. This is a recent departure from a single story, mono pitch design due to news that our family will be +1 in October/November :)

    The house is to be built on our croft with grant assistance from RPID, who've deemed that our current dwelling would be uneconomical to renovate. I have a 'pre-planning account' open and have had our first visit from the planners just last week. They were happy with the location and build aesthetic, and we've had an initial report back from them to confirm this. No constraints noted. I'm supposed to be meeting with a draughtsman at the end of this week to have a formal version of my doodles drawn up, but will likely need to postpone this given that our design is being evolved to account for our growing family. So, that said - building warrants will follow. You ask about the floor construction, and i'll address that separately as it's something I'd really like some input on.

    @Skyewright: small buildings vs (no) building warrant. We've looked at this a bit, and as freeing as it sounds we'd unfortunately rule ourselves out of funding eligibility if we went this route.

    @Fostertom: 195 + 50 + 50 Rockwool :) Full PassiveHouse is attractive, but not realistic. So many people seem to end up chasing numbers instead of enjoying the build process and the eventual experience of living in their self build. I have a friend who's been self building for 15+ years because his design is complex to the point of it being unachievable! 'Self build' does indeed mean me myself and I and I'm fairly confident in my ability to deliver as long as I keep it simple, hence the stick frame and Rockwool. I'll be contracting/leaning on my neighbour who's a plant contractor for groundworks etc, and i'll bring in a sparky/plumber for any legal bits. I have a large poly tunnel on site for cutting the frame components in, and i'll be preassembling wall sections in their most basic stick form (ie uninsulated etc)and then positioning them with a telehandler. In terms of interim watertightness, I was hoping bitroc would do the job whilst I fix the external cladding, but this will need to happen before any work is done inside the shell.

    @ringi: I think you're spot on, the PassiveHouse model is a good one to borrow from even if you don't intend to end up with a plaque to put on your wall at the end of it. I don't fully understand how all the numbers fit together, but I'm hoping with some forum input that this'll become clearer.

    I'm keen to hear some ideas for floor and roof construction and detailing. At present I'm considering a suspended timber floor (shock horror!) as I'm not confident I can handle the quantities of concrete involved, or to contract services for a clever slab. I know what I'm doing with timber though, and it fits with the simple principles of the wall construction. Is it possible to achieve 'decent' insulation' and 'reasonable' air tightness if I go down this route? All suggestions welcome....
    •  
      CommentAuthorfostertom
    • CommentTimeMar 15th 2017
     
    Great to hear you're not completely single handed, and using telehandler etc. Sounds good.

    About PH - it's a complete fallacy that PH = complexity; on the contrary it can be a design discipline that relies on simplicity in many ways, to succeed. Plus you need to select a non-complex Ecobuild or near-PH construction approach anyway.

    You don't have to go for PH Certification - you can just build to PH standard to your own satisfaction.

    What a rigorous PH design approach will give you, is guaranteed-result extreme fuel economy, as long as you don't willfully frustrate that in use. Equally guaranteed comfort and health in use is the thing that heads occupants off from practices that frustrate the PH promise.

    All this can be done at equal, some say less cost, than 'traditional' construction - but you do have to invest in the design stage.
    •  
      CommentAuthordjh
    • CommentTimeMar 15th 2017
     
    The best floor type will depend on your ground conditions. I think the main hassle with a suspended timber floor is that you generally need to keep the timber 150 mm above the ground, and if you then add perhaps 300 mm of insulation depth you need to get clever or lucky to achieve anything approaching a level entrance threshold.

    One way to build with good continuous insulation is the tea-cosy idea. Build a timber frame, or a block wall, and a roof with sarking and then add a layer of insulation wrapped all around the outside. EPS is the default for this external insulation. With a timber frame, you can also insulate between the studs with rockwool or whatever. That design keeps all the timber away from the cold and wet. You can clad the outside with whatever you like.

    It works well with a passive slab, which is a concrete slab sat on EPS, or rather in a very broad shallow bucket of EPS. The sides of the bucket join up with the tea cosy to provide unbroken insulation. It's actually quite easy to build as long as you have some people who know how to pour a slab. As you can probably tell, I'm a fan, but I don't know whether it will suit your situation or not.
    •  
      CommentAuthordjh
    • CommentTimeMar 15th 2017
     
    Oh and according to http://howtopassivhaus.org.uk/subject/ground-floors

    "Suspended timber ground floors are not advisable for Passivhaus buildings, because of the inherent moisture risk and complicated detailing required."
    •  
      CommentAuthorfostertom
    • CommentTimeMar 15th 2017
     
    What kind of moisture risk I wonder?
    •  
      CommentAuthordjh
    • CommentTimeMar 15th 2017
     
    Presumably because you need some framing underneath to hold the insulation up.
    •  
      CommentAuthorfostertom
    • CommentTimeMar 15th 2017
     
    So? Am I missing something? Suspended framing of course, not propped off the ground.
    • CommentAuthorTullich
    • CommentTimeMar 15th 2017
     
    Whilst I like the idea of passive type slabs, I think i'd struggle with the reality of one. Not least of all because I don't think the EPS components would be readily available up here, and carriage would be expensive due to their bulk.

    As far as any concrete work goes i'll probably pan mix with a tractor as I have a quarry for aggregate and an agricultural merchant for cement pretty much on my doorstep. I can then get around a whole load of (costly) access issues that premix delivery would entail too.

    Threshold levels would be tricky with a floor stuffed with Rockwool, but as the front of the building will eventually have a deck poking out of it above a downward slope, it shouldn't be too much of a worry. The back of the building where the main entrance is going will be more difficult for sure.

    In terms of suspended floor construction, I was expecting a few more cries of "blasphemy"? It seems like nobody builds like this anymore - why is this? Surely if you can sheath underneath the joists like you might on the outside of a TF wall, and can add plenty of ventilation it's really no different than a horizontal wall?

    If you could rest the joists on the bottom plate of the wall panels you'd have (relatively) continuous insulation through this area too?
    •  
      CommentAuthorfostertom
    • CommentTimeMar 15th 2017
     
    Yes, great idea - what's the snag? Apart from having to think a bit
    • CommentAuthorcjard
    • CommentTimeMar 16th 2017
     
    Ask your building inspector why no one does this any more
    • CommentAuthorcjard
    • CommentTimeMar 16th 2017
     
    Ps; if you're having a child soon, do hand off work to other people. I missed most of the first 3 years of my son's life because I was self building him a house. I saved myself at least £30k, but I increasingly feel it wasn't worth it
  1.  
    Morning and welcome Tullich from a croft on Raasay, much sage advice here and bare in mind I'm no builder or expert but you will not get a new build with worse access than mine. On an island off an island ten miles down a single track road and more. We've been just over a year in our 'off grid' all electric new build which isn't PH but extremely air tight with an 'intersteller' EPC, the best anyone has ever seen :-) We went concrete slab, UFH then polished the slab ourself, tis absolutely brilliant for a working croft, always warm, easy to clean and will save you a fortune on floor coverings. It's a bit 'industrial' and far from perfect but we all love it. The whole lot was mixed and poured overnight using the telehandler with a mixer on the forks. The house is 120m square so 70m square would be almost half the amount I guess.

    Good luck, Paul
  2.  
    Posted By: TullichIn terms of suspended floor construction, I was expecting a few more cries of "blasphemy"? It seems like nobody builds like this anymore - why is this? Surely if you can sheath underneath the joists like you might on the outside of a TF wall, and can add plenty of ventilation it's really no different than a horizontal wall?


    Standard construction here in Canada - but everyone builds with a basement (which has a concrete slab floor). Many people do the "semi-basement" thing where they only excavate to half the depth - so you have still have windows - this also works well on a sloping site. Basements are great as you get "free" storage space or "bonus rooms". Pre-manufactured timber frames are the execption here - most people do "stick build" - though roof and floor trusses will be pre-assembled and may need a crane to get into place.

    Paul in Montreal.
    • CommentAuthorringi
    • CommentTimeMar 16th 2017 edited
     
    I don’t see how transporting a lot of EPS will cost more than rockwall, you don’t need special EPS shapes for a passive slub, they just make it easier and avoid the need to build form work round the outside of your slab to hold the edge EPS in location while the concrete sets. Even if you had to hire a luton to transport the EPS yourself with two nights in B&B it would not cost that much. (Then load onto a tracker trailer.)

    However if you wish to use wood, as you has a slope to the back of the house (and hence free drainage) can you dig out the ground so that the top of your floor will be level with the ground at the front? Maybe even use some of the soil to rise the ground at the front. You would need some sort of retaining wall, say 2 feet away from the house wall edge, than built as a Segal on pod foundations.

    Or put a sloping deck on the front to provide level access to the floor about 2 feet above ground level, the ramp must not be more then 1 in 12 for wheelchair access regs (Part M), but can run along the length of your home with steps the bypass it for everyday usage.
    • CommentAuthorringi
    • CommentTimeMar 16th 2017
     
    Thinking about this more, as you have very cheap concrete and a “free” way to mix it then lift it to a height, have you considered making formwork for the walls (say in 50cm sections) and just filling the formwork with concrete, letting it set, then moving the formwork up for the next section? (EPS EWI could then be used)

    This gives you very robust airtight walls provided the concrete is correct compacted, with high thermal mass, without needing any bricklaying skills and using the quarry you have on site.
    •  
      CommentAuthordjh
    • CommentTimeMar 16th 2017
     
    I just had a look and the Passivhaus Details book has an article about moisture and ground-facing elements in passive houses. It's complicated so you will need to read it yourself but it definitely makes me nervous about suspended timber floors with lots of insulation in them. I'd want an expert to vet anything I planned to build.

    Don't forget that underneath a floor doesn't see the sun in the same way a wall does, so drying conditions are different.
    • CommentAuthorTullich
    • CommentTimeMar 17th 2017
     
    @ fostertom: Go on, what is the snag? 🤔😀 What am I not seeing here?
    @ Cjard: I have and he's fine with the idea in principle subject to a few details. Completely appreciate your point re lost time with little ones. The issue here is that if I don't do the work we simply can't afford to do it. The alternative therefore is to do nothing and continue living in a static caravan - so not an option at all!

    @camillitech: your build sounds really interesting and also like a logistical nightmare! I'll definitely be in touch with you again i'm sure.

    @ Paul in Montreal: ahh, good old fashioned common sense....

    @ ringi: standard eps, no. I can get it straight off the lorry from the buildera merchants the same as any other material. Anything "specialist" though will cost a fortune to transport. Three days of vehicle hire, accomodation and collecting materials that I can't afford to have delivered, and don't have the confidence to use doesn't seem like a great use of time. I could complete an entire suspended floor in that time.
    Your suggestikns re ground levels etc are VERY interesting though....
    I love your concrete bunker idea too - it's bloomin' windy here!

    @djh: That is a bit concerning.... where's an expert when you need one?! Good point re direct sun too.
    • CommentAuthorTullich
    • CommentTimeMar 17th 2017
     
    Excuse all the typos - fat fingers vs tiny screen keys - sorry.
    •  
      CommentAuthordjh
    • CommentTimeMar 17th 2017
     
    Posted By: ringiEven if you had to hire a luton to transport the EPS yourself

    I'd check the volume very carefully before committing to this plan. My EPS was a full artic.
  3.  
    Posted By: djhMy EPS was a full artic.


    So was mine!
    • CommentAuthorringi
    • CommentTimeMar 18th 2017
     
    Be careful with sheet insulation from buildera merchants, I have yet to have a load without damage, as they lift it with the same grab as they used for bricks.
   
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