Omnibuswoman

Picture of front noggins

Another roof-related panic question: when we fit the roof ply (today), does each sheet need to be in contact with a joist/rafter at each corner - ie do the edges of the sheets need to sit at the joist centres just as the wall ply did?? we’ve added external noggins of 22cm which throws my beautiful calculations out as to starting at the front corner and working back in whole sheets. If I do that, the edges won’t be at centres because I’ve added 22cm on the front….

Impressive!!

Problem solved, courtesy of Ali Dymock's amazing YouTube videos and the span tables linked to above. We need 10x2s for the 4.6m span, and will put in some noggins for stability/to better support the roof. 18mm ply on top, with EPDM over that. It actually looks achievable now, although we only have until the end of the day on Monday which might be a challenge. I can see that Ali Dymock left his garden room wrapped in tyvek membrane all winter, so if we run out of time to do the cladding it won't be the end of the world as we can return to it later on. Where would I be if not for the buildhubbers?!!

Thank you all. I am on-site now but will review these suggestions tonight when we finish. We are working on our corner posts now and I’m delighted to find everything is perfectly aligned and square ?

Quick update, and bit of a panic about the roof.... We have three of the walls done now - 1750mm studs (2x4s) with top and sole plate, fixed into the blocks with hammerfix screws. Overall height is 2310mm which feels generous for my height (1.6m) and even adequate for HWMBO. So far so good... We are going to move on to the front wall today, but I have started thinking about the roof and panicking that my design isn't sound... The workshop is 6.5m long and 4.6m wide. I had planned a ridge plate (2x10) with 2x6 rafters coming up to meet it, covered in 18mm ply. I ordered two 3.6m lengths of 2x10 for the ridge plate. I started looking at how to fix them together, and then had a panic about the roof design not being sufficient and collapsing in and killing us all.... So now I'm considering whether to do an almost flat roof by adding an extra top plate on the right hand side, and running timbers across the 4.6m width sloping down slightly to the left hand side. I spent a lot of last night looking at roof trusses and the design of trusses, but it looks quite difficult to get right, and I'm still worried about the roof falling in. Any and all thoughts will be hugely appreciated!! Photos of progress to date attached...

yes we will, just to be sure. I’ve read horror stories of errors that have only been detected after completion leaving the house under-heated.

I second this. We are building a near passive house and the key to this is air tightness.

No, he left Camborne for London in the early-mid 90s His mum was a local youth worker. His dad is a bat expert, so some of you may have come across him in the planning process!! His dad actually helped me out when I had a phone call from Cornwall Nature Police after a vindictive Neighbour tried to report me for “crimes against bats” when we had a hedge trimmed!! (The only bat nearby was in fact the Neighbour herself...) I was deeply moved by Don - his hard work and compassion. He had just lost his wife when the programme was made. Incredible man! Where is the G8 being held? Scrub that - Carbis Bay! You did say that. Sorry!

thank you. Should I put a layer of plastic sheeting between the ply and the stud, or just tape up the ply joins?

Down near Camborne! My boss (in London) is from Camborne. He comments on how people imagine Cornwall is just a county of pretty fishing villages with no rough bits, but there was an excellent TV programme featuring Camborne food bank a few months ago. Simon Reeves I think. It really highlighted rural poverty and social exclusion.

No, I got muddled between breathable membrane and VCL, so have gone with breathable membrane around the outside of the stud walls. Thanks for the advice about the roof. I’ll see if I can drop some of the ply from the order and get some OSB for the roof. This forum is worth its weight in gold!! I don’t know what I would do without your fantastic input!

Walls are 45x95mm stud walls with 9mm ply on the inside, a breathable membrane outside, battens then shiplap cladding. 45x110 depth rafters up to a central main beam (45x2200). 9mm Ply on top of the rafters, EDPM roof covering.

Many thanks HTH. I have cancelled the OSB order and reordered the pine ply, which he assures me is structural, and is 60% of the cost of OSB. I have identified Tyvek as a popular breathable membrane choice, which seems it will do the job. Quick question: is it important not to have the insulation touching the ply or the membrane, or does it not matter? Thanks! M

I've managed to track down 30 sheets of OSB from a local builder's merchant. £25 a sheet plus VAT - almost £1k!! But I'd rather get it right and have the workshop outlive me than see it decay and feel that I could have done better. The chap from the BM said prices have doubled recently....?

Thank you all for your excellent contributions. I have now ordered the wood (a rather eye-watering £2400, but it is quite a big shed!) and have a couple of outstanding questions... The timber store couldn't supply the 30 sheets of 2.4x1.2 11mm OSB 3 that I wanted. He said it is really hard to get hold of OSB at the moment, and offered me 9mm pine plywood sheets instead. Will these be adequate? Or should I go on a search of the south west for OSB? I found this product at Wickes: Is this the correct product for the membrane between the stud and the cladding? Insulation - looks like I will use mineral wool. Will 50mm depth suffice, or should I be stuffing the frame with 100mm? The workshop won't be an office or anything, I'm more interested in stopping it freezing over in winter and boiling in summer - it is basically a rather large shed. Many thanks!

We didn't go with an architect in the end. We did speak with one recommended to us, but in the end we felt that we just couldn't spend that proportion of our modest budget (around 10%). Instead, we used the questions the architect had asked us to think about - how we plan to use the house, what our living habits are, feelings about 'must have' things and 'absolutely not' things etc. I used an app called Room Sketcher to map out plans, based on a simple rectangular house (which we understood was likely to perform well as a passive house and was likely to be the most cost efficient to build). Once we had completed that, our builder engaged an architect that he works closely with to draw our plans up properly, and then I spent a couple of hours meeting with him to make a few final adjustments. We have spent a total of about £3k, which is 1% of our budget. And as a result of doing all of the thinking and planning ourselves, I now know the plans for the house upside down and inside out! It was definitely the best thing for us, and has helped me to gain a sense of ownership both of the house and the project as a whole. If you know what you want, I would recommend this way of approaching it, and maybe getting an architectural technician to draw the plans up for you.

Hi there, welcome to the Hub. I am one of the members building in East Cornwall. We bought a plot in South East Cornwall last year, with extant planning permission. We’re building a timber frame passive house, ASHP, MHRV etc hopefully starting the build proper in the Autumn. Buildhubbers are a friendly and generous lot offering invaluable advice and encouragement, sometimes a gentle reality check, and plenty of banter. ☺️

Thank you all for your replies. Such a huge encouragement and brilliantly useful info. The concrete slab has a DPM /radon barrier under it as we’re in radioactive Cornwall ☢️, but I will also put a membrane under the sole plate and will take the cladding down over it. I’ll post some pics and words as I go along. And will do my best to enjoy the process!! ☺️

Our builder was going to build our workshop for us, but is now too busy and I have decided to crack on and do it myself. I have never done anything even remotely as challenging as this - putting up shelves has been the limit of my previous DIY experience - so I am quite apprehensive. HWMBO and my son have been roped in to help, and my dad will also come along to tell me what I’m doing wrong ?... The builder has laid a reinforced concrete base, and two rows of breeze blocks around three sides as follows... I will build stud walls (2x4s at 600mm centres) up to a total height of 2.4m. First question: how do I fix the wood frame to the block wall? I was planning to build up the wall by facing it with 9mm OSB boards, then a waterproof membrane, battens, and finally shiplap cladding. The builder has advised me to put the OSB on the inside of the wall, not the outside, then to batten a membrane to the stud wall and clad on top of that. Second question: what are the advantages and disadvantages of each method? Is one better than the other? We may put insulation into the wall at this point (something wooly) or wait until the house is insulated with blown cellulose an insulate it with that. The roof will be a gently sloping apex roof (12 degrees), with a central beam and rafters, strengthened with a cross brace. I planned to put OSB on top, followed by corrugated roofing sheets, but I can’t see how I will close the gap between the top of the rafters and the top of the walls. Question three: Should I put the OSB on the inside of the ceiling instead, and then fix the roofing sheets to the top of the rafters?? I have been offered some second hand windows for it, and I think I have worked out how to build the frames for the windows, and plan to put in both large double doors at the front and a small door near the back for quick access to the freezer. Does anybody have any tips or tricks for framing and fitting windows and doors?? Any and all advice and encouragement gratefully received!!

what a great idea!

Thanks Dave. I will pop an email over to my friendly planning officer now! Does notifying building control have any bearing on the planning consent deadline at all? I’ve had conflicting advice about that (from planning and building control depts). M

We have been increasingly anxious about the approaching deadline for the existing planning consent to expire - mid March 2021 - but today, at last, Dan our builder has made a start on the foundations for our workshop/garage/temporary site office and storage space. A large amount of hardcore arrived, the fencing around the protected oak trees was erected, and a digger and dumper arrived. Dan suggested making a start by scraping the mud off the driveway which was turning into a quagmire - an excellent idea. The hardcore is in place ready for levelling, and on Friday the concrete foundation slab will be cast. Plans are afoot for disposing of all of the topsoil that we had scraped off back in October. This is one of our planning conditions: to remove soil imbibed with arsenic compounds and replace with 'clean' topsoil. We have engaged a fantastic remediation company, Remediation UK, to do this. They sent us two brilliant guys to do the scraping, and piling it all up in an enormous 60 ton heap. Hopefully next week (council permit processing permitting) they will be back with an enormous skip to load up and take it all away to their disposal site down beyond Truro. Of course, I am 250 miles away, locked down at home, and am only able to supervise via phone calls with Dan, and his photos (attached). But one thing I was able to do today was to meet with a company specialising in passive house engineering (Greengauge) to start talking about the PHPP spreadsheet and whether or not our window plans might cause overheating. We chose this company because they have made some really radical commitments as an organisation to only work on enerphit and passive house projects, and they are committed to climate crisis action. So far so good - second meeting in two weeks to review the results of their calculations... I'm now wondering when the right time is to dig a utilities trench. Anybody have any advice about that...?

All progress is some progress! We are in a very similar situation with living in the south east and building in East Cornwall - we haven't been there since October when we had the topsoil scraped off (one of the planning conditions as the area has raised levels of arsenic in the ground). We can't wait for lockdown to lift so that we can get down and start some work.

I'm looking at a Land Rover defender 110 on bidspotter, and wondering whether other people have bought things through bidspotter and if so what your experiences have been? I've found very little by way of reviews online, and am concerned about spending money on something I can't go and view. Thanks! https://www.bidspotter.co.uk/en-gb/auction-catalogues/assetauctions/catalogue-id-midlan10896/lot-4876e8a3-3c9d-421e-a56a-acaf00ab5a2c