Nick

Thanks for the reply. Your blog is actually one of the few sources of info I'd been using to put the build together but havent read it start to finish yet. Helpful to have you explain the costs in more detail. My build plan is similar - room in roof & large void with the roof held up by a large laminated ridge beam. Appreciate the tip on the two companies. Without wanting to rake up too much, who is running the show at MBC since they parted ways? Who would you recommend speaking to there about specifications and quoting?

Hey all. The design I'm planning for my build has shifted towards a twinwall or i-beam timber frame with a passive slab. Just seems the most tried and tested way of getting a good thermal envelope on a budget. My question is, has anyone got any costings for seperate elements of a build like this (passive slab, external walls, internal walls, roof, e.t.c) that they'd be willing to share. I appreciate that prices fluctuate over time, i just want to get a ballpark so i can create a plan that is roughly affordable before i draw it in detail and start getting formal quotes. I dont want to put off the builders by asking for a load of quotation work on a design that is still completely up in the air. My build involves a huge, full height room that occupies half the footprint of the house so trying to work out costs on a traditional all-in £ per m2 of floor area just isnt cutting it as there is a huge proportion of external wall & roof per square meter of floor. The spec & cost breakdown that Viking/MBC have on their website (http://www.viking-house.co.uk/selfbuilder-package.html) would be exactly what i need if they just gave the dimensions of the house they were building for that money so i could compare. Any help appreciated as always.

That's a v.good idea. In practice, it may only make sense for things which will fit in a car or small van but which couriers won't take. Very heavy or very delicate items spring to mind. There are a lot of great collection-only deals on eBay which this could help with. Will do what I can for the Herts area.

Won't be a problem to get it made. Getting it up to you cheaply is the only issue. If you want, give me the sizes and I'll let you know when I'm back in the office.

Dave, I'm sure one of our suppliers would be able to do it. They're all in the Midlands or further south though and couriers won't take glass (unless it's a tiny unit and you can wrap it up sufficiently to disguise it as something else). If above normal parcel size, do you have a way of getting it to you in the Highlands? If so, PM me details and I will try to sort you out a price. When it comes to U-value, no-one will have specifically simulated a TG unit with a stained glass middle pane but for triple glazing generally, you can get the u-value as low as 0.2W/m2k by adding a heat mirror pane and Krypton fill. All depends on how much cavity you have and what you're willing to spend. To get to 0.2 you're generally looking at a 60mm unit!

Hi All. For those of you I haven't had the pleasure of speaking to yet, I'm planning a self build but during the day I'm chief technical at a fairly large manufacturer of windows/doors/glazing based in London/Herts. A few of you have PM'ed me with glazing questions so I thought it best to make a separate thread for sharing any info. If anyone needs help with technical details, specification, getting trade prices, e.t.c. fire away. My way of giving back for all the great construction advice I've already received here.

You'll want to use glass. Polycarbonate has some useful properties but ultimately glass will look the part and weather far better. Its just a case of specifying the glass to be sufficiently strong and then looking at the implications for weight & cost. 4 toughened sheets wont help strength if that's your concern. You'll want thicker individual sheets to resist wind, gravity and (depending on pitch) snow loads. That span could even be done in one sheet but splitting it as you've done is the sensible way to go for cost. Off the very top of my head. It will need to meet a design wind load of at least 1.5kN/m2 in an open barn style structure though i could be mistaken. Your glazing supplier should be able to advise on this and help you specify the glass.

OK I follow. So the options are basically a standard post & beam construction or an all engineered timber construction but there's no sense trying to mix & match (plus potential issues with different rates of expansion between the two types). Have done a fair bit of research over the last day and I think I mostly understand the basics now. The detail the TJI manufacturers seem to show for the first floor has the floor joists sitting directly onto a laminated header / beam, an engineered rim board all around and the second floor cill plate fixed on top of that with squash plates to support the joists where there are point loads. Playing around with drawing that detail for my build it seemed like there could be some cold bridging through the joists as they were now in contact with the ventilated cavity of the rainscreen, bypassing all the insulation. Also looked like it would be very challenging to keep the VCL continuous having to tape around all the beam ends where they penetrated the inside sheathing of the wall. Putting the joists on hangers seems a good enough solution to both. Then decided to have a go at drawing a solution that used the I joists everywhere instead of glulam beams for (potentially) less bridging and a structure that could be unitised so I could make frames off site that would just stack together for quick assembly. Basically instead of using a solid beam everywhere, the idea was to use I-joists so they can be fully stiffened with OSB at the fixing centres (where the studs attach and the floor joists hang), and fill them with 2x40mm PIR everywhere else. That way 2/3-ish of the solid timber is replaced by high quality insulation to compensate for the bridging. About halfway through drawing it it started to look like overkill (assuming the joists are even strong enough when loaded that way), but I thought I may as well finish the detail to see what you all think - it's only a quick swap to put the glulam beams in. D-Foundation & Ground Floor Wall Junction.pdf D-External Wall & First Floor Junction.pdf D-External Wall Detail.pdf

Thanks Ferdinand - I'm looking for about 9m unsupported too so that's really good to know. I take it it was built recently? All engineered timber build or other materials too?

Cheers Peter, will email you now. 40 metres is pretty amazing. Are we talking 40m span on its own or as part of a roof construction including joists & other supports.?

That's a great looking build and an amazing amount of space! The photo definitely helps btw. I completely hear what you're saying about doing a timber build. I went for the steel originally just because of the span but if it can be done with engineered timber than that's my preference. Guess I won't know 100% if the Glulam will do the job exactly the way I want it until I'm at the point of paying a structural engineer to design everything properly so I'll keep the steel portal version in my back-pocket just in case there's an issue, and make sure my budget covers either option. Just realised I never answered your question about the roof - given that budget is priority number 1, I'd happily use cement particle board or another lightweight board if planning don't raise any objections. I didn't think the weight would be too bad. Neither me or my other half are worried about kerb appeal or having a house to show off on Pinterest so a neat & tidy design that's warm with plenty of space is all we're aiming for. Am re-doing all the basic details now to suit timber only and already it feels ten times easier - no worrying about how do I fix A to B, how do I stop X cold-bridging Y, e.t.c. They only thing I'm not sure about is how to design the load bearing external and internal walls that will carry the roof, floors, e.t.c in timber. Will have to start doing some reading on that later on. Broadly, given the choice would you design the whole envelope using I-Beams and adding Glulam joists for large spans or is there a more cost effective way of doing it by mixing/matching standard timbers or other materials?

Are yeah... I've built a few "features" in my time

Was just going to dry line TBH. We aren't fussy people Will look at the pallet prices nearer the time for sure. The other aspect is that I have a few friends in the building trade so stuff that is fairly standardised and can be bought at every builder's merchants/wholesaler (like plasterboard & OSB) I should be able to get an even better deal on if i really try by pinching their trade discounts or finding someone who has some unused pallettes. Proprietary/exotic materials tend to be harder to get bargains on so I'm trying my very best not to design them in unless I really have to.

Also could go the the less neat but easier to retrofit way of fitting the joist hangers ready to go and then just boxing around them for now.

I'm slowly weakening to the idea.. though still can't shake the suspicion you all just want me to break my neck It really does look like good stuff and the 1200x1200 board should be doable but it's nearly double the cost of one 12.5mm plasterboard and one 11mm OSB by my reckoning. If by some miracle there's any money left in the pot by that stage I might go for it. The main lesson I've learnt so far with costing is that every time I see a better way of building something, the best thing to do is close my eyes and run from the screen before it sinks in as sooner or later I'll convince myself that I need to use it - the m2 cost just creeps up and up even though deep down I'd be happy enough just to be able to have the place built with no insulation and no plasterboard.

Cheers Ian. Really appreciate you giving the benefit of your experience here. My fault, I should have made the design clearer. Very roughly, Imagine an 18m long x 12m wide steel-barn. Split it into two so you end up with 2 areas at 9m x 12m. I'm looking to get one of those areas full-height without columns, and one 2-storey. If 12m was just too far to span, I could reduce the design to 9m width and maybe add an extra bay or two to get that floor area back. Those sizes are why I assumed (probably wrongly) that the portal frame was the only way to go. Not sure on the number of bays - was under the impression I would have to bring them closer than the agricultural-standard 5m for stability - the BarnHaus uses 4 bays at around half my build length so I was thinking I would end up needing 8 bays. This smaller span was why I didn't think about the braces. Yes, the rough plan so far was to line the underside of the eaves with a timber header and run suitably strong beams (maybe gluelam) between each steel at ground floor level. That would have allowed the I-beams to tie-back at these points with the standard brackets and span ground to eaves all the way around the building in continuous lengths thereby making getting the envelope up and watertight fairly quick & straightforward. Needed the I-Beams to be 300mm min anyway for insulation reasons so being able to run them full height seemed like a good bonus. The first floor (also I-Beam) was going to have a perimeter beam fixed to the inside of the steelwork at first floor level to hang from, and then rest on two rows of additional steel stanchions coming from foundation level so that instead of having to span 12m, it only had to span 4.75m, 2.5m & 4.75m. These additional steels I was going to box in / insulate and hide within internal walls (seems similar to what you described). Still would be great to go with enclosing the steel within the wall from a simplicity point of view if there was a way to get the racking support without changing the wall position. Do you think there's any way that sheet material (DHF? Ply?) could give enough support if it was beefed up and fixed at regular centres? The more I think about it, it might not be that bad running a diagonal brace through the OSJ web - just a case of a hole at a different height for each of the 4 I-Beams that make up each bay - should be consistent across every bay so could be measured & drilled on the ground alltogether and just lifted into place. Working on detailing this in CAD now so will update the thread with it soon but hopefully you get the idea? If the portal frame is going to be too complicated I may just try to start again in timber and use steels only where needed for spans as you've suggested. If/when you get the chance would be great to see an example of the timber build on your place.

Late to this party but subscribing to see what your supplier says Joe!

Ian, Thanks a million, this is just the sort of info that will steer me the right way. Still basing everything on the portal frame so far. Did wonder whether the span was doable with another solution. At this stage I'm trying to pin down prices for as many things as I can that I know with some confidence will work. Once I've got an overview, my plan is to try and chip away slowly at the design to get within budget. The roof I have planned thus far is a mild pitch steel-barn style but I'm not wedded to the idea. Whatever can achieve the span will be fine by me although I'd imagine it would be easier to get PP for a pitched roof that could be disguised as a standard house construction. Roof runs parallel to the shorter dimension of the room (spanning the long dimension). The Structural I-beams were there to take the wind-load right up to the eaves height (which I took of the JJI span chart) but I overlooked the diagonal steel members Could technically run them through the OSJ webs I think but would be a nightmare. Was planning to try and run the beams to support the first floor on the inside of the steelwork so they're not clashing with the bracing. Any chance the I-beams could be replaced with 2x shallow stud walls allowing the steelwork to stay in the middle? Does your solution have the steelwork sat between the cladding and the insulated wall? Thanks for the airtightness solutions. Passivehaus guide seems to suggest the VCL can be achieved just by taping the joints of the inner OSB so that might also be an option. When you say the DHF board could be racking support, do you mean to the exclusion of the steel braces or just additional racking support to keep the timbers stiff? Sorry to bombard you with questions but nice to meet someone who has already been there / done that with the design you're looking at.

Good point. Doubt I'll actually go with the cellulose though. Would like to if it was similar cost to rockwool/knauf or slightly more but looking around I can;t seem to find many active suppliers so far unless anyone has any they can recommend?

Agree - definitely a plus. The slightly lower U-value would be fine with me as the mass/airtightness benefits will I'm sure outweigh it. I'm putting the studio room north facing with as little glazing as possible (all openable though for ventilation) and low G-Value units to keep solar gain down to a minimum. Hoping the reversed heat pump and HVAC will take care of the cooling on the occasions it does heat up. There is a clear path from one end of the building to the other so can always open all the windows doors to vent through the whole house.

Thanks for the suggestion. Looks like solid stuff but TBH, as I'm trying to save cost and do as much as possible solo, it makes more sense to stick with two lighter, cheaper boards I'll actually be able to lift

Thanks chaps. Just done a bit of reading onto the cellulose now. Really like the idea of it filling the void completely and drying solid which will stiffen the construction. Overall U-value will be a little poorer at 0.13 but not too concerned about that. Less keen on the idea that it could be corrosive to metal and could potentially absorb moisture and degrade if there is ever a leak. Much of a muchness really though - will have to come down to price in the end as once I seal the wall I'll forget all about what's in there. Whatever it is has to be 100x better than the flat we're in now so i'll never notice. Either of you have any idea of a rough m2 or m3 rate? I think the idea of the different thicknesses is that a noise only gets cancelled out when the material it's travelling through corresponds with its wavelength. Having one 6mm , one 9mm and one 12mm OSB should therefore in theory give better acoustics than three 9mm's. Like you say though, easier and cheaper just to order one size by the palette and not worry. The electrician will be my brother-in-law (though he doesn't know it yet ) so he'll have to hold his tongue. The room is going to be used as an actual studio on occasion and the ability to have something heavy on a wall bracket rather than having to set up a huge stand makes it well worth sticking the Ply/OSB behind the plasterboard at this stage for the little extra it will cost. Will also add a bit more mass to the wall which doesn't hurt for acoustics.

Cheers. Will look into all of those suggestions tonight! Will definitely get it signed of by an SE don't worry. I don't trust my drawings and I'm the one who has to live there

Thanks Dave. All very helpful stuff. With you on the service void 100% Would you be happy switching the Ply that's backing the plasterboard to OSB? I've always used ply to go between joists & battens as it seems a bit stiffer and more hard wearing but I'll bow to your knowledge. Finally (I know this is pedantic) but have you ever bothered using sheets of different thicknesses when building a wall to try and cut down sounds of different wavelengths, or not worth the effort?

I read (think it was the Passivehaus design guide) that because of the number of protrusions through the inner wall on a steel frame, putting the VCL on the outside was acceptable as it's less complicated to design in. I'm thinking now though that it might be best to put another OSB on the inside of the wall, then battens to form a service void, then the Ply (maybe reduce it to 12mm) and the plasterboard. That way I could move the VCL to the inside and it would be simple to join up with the floor & ceiling if I repeated the detail there.