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?

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?

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.

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.

@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....

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.

What kind of moisture risk I wonder?

So? Am I missing something? Suspended framing of course, not propped off the ground.

Yes, great idea - what's the snag? Apart from having to think a bit

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

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.

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.

@ 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.

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.

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.