pir8ped

That's settled then. I'm using a structural engineer. Yours! Cheers.

I think that was the picture that set me thinking down this route. It's all your fault! I wasn't sure that your portal frames might have had some beams or columns placed afterwards. I wonder why use 18mm ply both sides, when it was bonding onto presumably something like a 9-12mm thick web. From what I've seen in images about joining I-Beams, the joining plates aren't meant to go from flange to flange, but leave a few mm spare at the flange that is likely to be compressed under load. I think I saw that in the JJI booklet.. Not that I'm telling you how it should be done! Obviously, you've done it and it works. Just speculating on why it is the way it is. Wonder if 9mm OSB both sides might do? And it looks like the glue used both to attach the flanges to the web and the joining plates to the beams is the foamy polyurethane glue. I've used that a lot in boat building and have never seen it fail. Under stress and for a few years. But I was wondering if I might use Cascamite or something similar for the I-Beam construction, for more proven durability. Maybe foam will do! Thanks for this.

I went to sleep daunted at the prospect of really testing the portal frames myself, or paying someone else to do it, but also at the prospect of using a beam under the rafters for support. The beam would be pretty big and heavy (AI did a quick calc and said 360mm deep), and I'm most likely putting up the building alone, and then I'd have to think about suitable supporting columns for the beam So I've continued along the line of incalculable designs, and made the connections at the peak of the roof as strong as I reasonably can. There's a loss of headroom under the peak (which only matters over the mezzanine area) but as drawn it's less than the beam. And I could make the gussets and blocking pieces in a batch, glued and screwed together and I think it would aid and simplify the construction. peakSupportStructure2.PDF

Mine is 6m wide too. So how were the joints made at the wall/roof joins, and at the roof peak? Did you support the roof peak with a beam, or was all the load taken by the portal frames? On the front of the PH15 booklet, there a picture of IBeam portal frames used to make a house with a big beam supporting the top of the roof. I might have to use a beam after all, but that would spoil the head room in the mezzanine bedroom area, unless I raise the roof a big higher, which I'm reluctant to do. I haven't ruled out having my I-beams made for me. It'll depend on the quotes.

It's not a shed. It's a house, so it needs insulation. Temperatures vary between 40 degrees and -7. I want to minimise my heating/cooling costs, so we're looking at 300mm thick insulation and minimal cold bridging. I've built a shed there already, which I live in while I'm building. It's 11mm OSB framed with 2 x 1. 25mm celotex in the walls. 75mm celtotex in the roof, and 100mm celotex in the floor. It's 4.8m x 2.4m floor area. It's fine it all weather except the top temperatures, when it gets far too hot.

Yes, no requirement for structural engineer, and no building control officer coming round to see it's up to spec. It's an opportunity to open a large can of worms.

I'm 67.

Well, if a structural engineer would turn away the task, might have to get really basic and test a frame. Does anyone here have any experience of load testing a beam or joint of any kind? I'll re-phrase that. A timber joint of any kind.

I think I read of an unwillingness of structural engineers to try to calculate this, as so much depends on the quality of the glue. I'd have thought the plates for the peak of the roof wood be sufficient. I mean, if I used a whole sheet of OSB to fill in the triangle at the peak, it would be overkill, so it's more a matter of how much of the triangle I need to fill. Naturally, I don't want to use the same approach at the sides, as there'd be a weird infill at the join of the walls and roof. Hence the idea of externalising that gusset by filling in the triangle between the rafter and the wall. Plus the plates joining either side of the web. Another option would be to fit plates over the flanges, using blocking pieces to join the plates to the web. Without filling in any of the triangle.

I've done no sketches of the joining of the I-beam webs. The max flange length in the frames is 4m, so I can use one length of timber for that. But my OSB sheets for the frames will be 2.4 x 1.2, so I'll have to join the webs together somehow. Butting, or a on OSB plate glued and screwed on one side, or a plate on each side of a join. Those are the options that spring to mind.

Thanks. I think it should be simple too - but I haven't really tried yet. I notice in those pics of I-beam portal frames I mentioned that the webs don't seem to be joined at all - just butted tother. Maybe that's enough, but I'd be inclined to add a 200mm wide OSB plate I think. Am I wrong? It would be nice to be wrong, so I can just butt them together to make the longer ones.

I'm planning on building a small house with an I-beam portal frame structure. The place is very sheltered and the whole area gets very little wind, but there's the occasional thunderstorm passing through which can have very strong gusts. The house will have an outer skin of 9mmOSB, glued and screwed to the flanges of the frames. Inner skin the same, but 18mm OSB. Insulation probably rockwool. More details of the general situation are in my profile. Part of the design intention is to allow me to do much of the work here in the UK - making the portal frames, doors and windows. I can take all the parts of the frames for the house with me to France in one shot with my van and trailer. (And yes, I've seen discussions about making DIY I-beams, but I still want to do it - having the 9mm groove in the flanges cut at a local wood engineering shop, and making up the I-beams at home.) I'm hoping to have all the structural stresses dealt with by the frames and the OSB skins. There'll be no interior walls except for a small bathroom in one corner. There will be a mezzanine floor though extending across the width of the building, up to 3 metres from the north wall. I anticipate this will to a degree stiffen the whole building, counteracting the forces that would tend to make the tops of the walls spread. This leaves the 5 metres or so of the southern end of the building with no interior structures, depending solely on the south end wall and the strength of the portal beams to keep its shape. I've seen photos of Patrick's portal frame house here, and Joe90's. Their frame joints at the tops of the walls and the peak of the roof seem to be just plywood plates glued and screwed through the web. I don't think the frames were the sole providers of the structural strength though - I think there were beams under the peak of the roof. Not sure. I've drawn the house structure in the attached pdf, showing general views and dimensions, and then some options for joining the angles of the portal frames. I'd welcome any comments or suggestions, but particularly about connecting the I-beams at the frame angles. Thanks, John portalFrameConnectionOptions.PDF

I've built a workshop/storage building on site so far, with all the slates and OSB brought from the UK. Technically, I might be charged VAT for a second time going through the border, but I happen to have found a crossing that gets me to the other side when the customs people are not at work so I'm waved through. It might not last, but so far, so good.

Hi, I've done quite a bit of building - renovations, extensions, replacing rooves. Always DIY, low budget, usually working alone. Built a tiny off-grid cabin in a lovely piece of a valley - 23 acres of oak forest surrounding a meadow which is full of insects and wildlife. I'm aiming to keep it that way, with a few fruit and nut trees scattered about. But we can't officially live there, so I bought a building plot nearby. The plot is nice and was cheap. The intention is to build a cheap timber house close to passive house standard. The plot is sloping 8 degrees, and I wanted a minimum of digging and concrete, so it's built on oak piles. The floor space is under 50 square metres, so I'm not obliged to hire an architect or structural engineer or have air-tightness tests etc. But I do want the house to outlive me, and as the builder I am responsible to correct any defects that appear in the house over the next ten years. So I'm here, mostly for feedback and advice. Brexit only allows me 90 days at a time in France. I'm generally happy to come and go (though the principle of losing freedom of movement offends me!). So some of the building I'm doing in the UK - making up I-Beams, and making doors and window frames, and taking stuff with me to France with my van and trailer.