efkor Posted February 4 Share Posted February 4 (edited) Hi, I'm on a first-time self-build in Cumbria and I have am about to instruct a timber frame designer. I intend fabricating the wall and roof cassettes myself and I'm unsure whether to replace the dimensioned timber studs with i-beams. Reasons to use i-beams are (1)reduced cold bridging and (2)avoids wrangling with bent/twisted timber. Initially, I was just going to replace the inner studs with i-beams but my TF designer says that I can replace top and bottom plates and the side plates too. He mentioned that I would have to add packer plates and that the window area would need to be boarded in ply. He didn't elaborate on fixings but I'm having trouble imagining how I'm going to nail up a cassette made entirely from i-joists. I've seen angled nail-plates in JJI brochures but this leaves me none the wiser. I've seen that a few of you have used i-joists. Can you give me some pointers on connections please? Or should I just stick to replacing the inner studs. Thanks for your help Edited February 4 by efkor placed in wrong section Link to comment Share on other sites More sharing options...
MikeSharp01 Posted February 4 Share Posted February 4 All I can say is that nailing them to achieve a 90 joint is no fun. I eventually gave up and where I have 90 deg junctions, around windows, I used Simpson strong tie 90 deg brackets with a backer piece in the reverse webs to take the screws. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 4 Share Posted February 4 When I get around to making my new shed, this is how I intend to do it. For a house some analysis of buckling will have to be done. 7 minutes ago, MikeSharp01 said: All I can say is that nailing them to achieve a 90 joint is no fun Adhesive bonding. Link to comment Share on other sites More sharing options...
efkor Posted February 4 Author Share Posted February 4 @mikesharp01 Your comment confirms my fears! Link to comment Share on other sites More sharing options...
efkor Posted February 4 Author Share Posted February 4 16 minutes ago, SteamyTea said: When I get around to making my new shed, this is how I intend to do it. For a house some analysis of buckling will have to be done. Adhesive bonding. A buckling analysis is another reason to avoid the i-beam solution Adhesive bonding is way less fun than nailgunning! Link to comment Share on other sites More sharing options...
Russell griffiths Posted February 4 Share Posted February 4 Why build them into a cassette ? stick build it on site and clad it in osb all on-site. theres 3-4 that have done this i believe. @Gone West and @Patrick Link to comment Share on other sites More sharing options...
efkor Posted February 4 Author Share Posted February 4 7 minutes ago, Russell griffiths said: Why build them into a cassette ? stick build it on site and clad it in osb all on-site. theres 3-4 that have done this i believe. @Gone West and @Patrick Yes, stick build is an option but the problem of the filler plates and the awkward i-beam to i-beam connections still remains Link to comment Share on other sites More sharing options...
Adrian Walker Posted February 4 Share Posted February 4 (edited) The PH15 uses I beams. https://www.phhomes.co.uk/ph15-projects/ Edited February 4 by Adrian Walker Link to comment Share on other sites More sharing options...
efkor Posted February 4 Author Share Posted February 4 13 hours ago, Adrian Walker said: The PH15 uses I beams. https://www.phhomes.co.uk/ph15-projects/ That's very useful, thanks Adrian. I see how they have minimised the number of troublesome i-beam to i-beam connections that are so prevalent in a cassette. They use a portal frame structure and hang the floor cassettes from the internal face of the 2-storey wall. Unfortunately, I can't use a portal frame solution on my site. Link to comment Share on other sites More sharing options...
MikeSharp01 Posted February 4 Share Posted February 4 2 hours ago, Russell griffiths said: theres 3-4 that have done this i believe. Yep that's how we did it. Link to comment Share on other sites More sharing options...
jamieled Posted February 4 Share Posted February 4 (edited) Our tf was built from JJI's. Get a copy of the James Jones technical guide. It details the connections. Where reinforcement was needed they were packed with osb and then nailed together. At right angles, such as window openings they were nailed like normal timber. Edited February 4 by jamieled Link to comment Share on other sites More sharing options...
dnb Posted February 4 Share Posted February 4 The Steico Joist technical guide might give some clues. I believe it covers use as walls - I plan to build my garage this way. Link to comment Share on other sites More sharing options...
Gus Potter Posted February 4 Share Posted February 4 3 hours ago, efkor said: Hi, I'm on a first-time self-build in Cumbria and I have am about to instruct a timber frame designer. I intend fabricating the wall and roof cassettes myself and I'm unsure whether to replace the dimensioned timber studs with i-beams. Reasons to use i-beams are (1)reduced cold bridging and (2)avoids wrangling with bent/twisted timber. Hiya. Well done you! it seems you are now getting into making big design decisions on the structure and how that interacts with all the other elements of the design. 3 hours ago, efkor said: Initially, I was just going to replace the inner studs with i-beams but my TF designer says that I can replace top and bottom plates and the side plates too. That all sounds great on paper but in practice unlikely to work given the nature of self building. It's your first self build so you have a huge amount to learn. I joists are good for carrying bending loads, say a floor. They are generally less appropriate for compression loads, say where you have openings with point loads from above. My advice is to avoid as the detailing and connection design will be horrendous / costly and unlikely to be "self" buildable. Take the hit on thermal bridging and consider standard solid studs or something like a space frame. @Kelvin has done a cracking job using a space frame and has lots of practical knowledge on how you make it work and the pitfalls.. to avoid. Link to comment Share on other sites More sharing options...
efkor Posted February 5 Author Share Posted February 5 2 hours ago, Gus Potter said: My advice is to avoid as the detailing and connection design will be horrendous / costly and unlikely to be "self" buildable. Take the hit on thermal bridging and consider standard solid studs or something like a space frame. Sounds like good pragmatic advice... when my TF designer said there's no problem in designing cassettes using i-beams, he was probably referring to work he's done for building firms. Maybe he wasn't considering the buildabiliity of it for a novice self builder like myself. I've seen the connection details in the JJI manuals and they are scaring me off a little. I might give myself a break, just do a "normal" cassette with solid studs, enjoy some straightforward nailgunning me-time and save the brainwork for other technical stuff, such as ASHP, MVHR etc 1 Link to comment Share on other sites More sharing options...
IanR Posted February 5 Share Posted February 5 (edited) 12 hours ago, efkor said: Yes, stick build is an option but the problem of the filler plates and the awkward i-beam to i-beam connections still remains I'm not clear on what you feel is the advantage of building your own cassettes. I'm not sure there are awkward connections, there's just different detailing required compared to using solid timbers, and yes, if you need to fit to the side of an I-Beam you're likely to need to pack the web out to the same thickness as the flanges. There's a significant performance advantage to an I-Beam (or twin-stud) structure, it's worth investigating further. If you've also got a frame designer lined up that's confident, it takes the burden off you needing to know every detail beforehand. I've got a pretty comprehensive 3D model of my frame and am happy to post images of any junctions you are not clear on. 13 hours ago, efkor said: He mentioned that I would have to add packer plates and that the window area would need to be boarded in ply. Ply lining the window apertures gives a clean surface for the windows to fix into and an easy surface to tape to for good air tightness. The I-Beams weren't packed out though, the ply "just" went across the flanges. Edited February 5 by IanR Link to comment Share on other sites More sharing options...
SteamyTea Posted February 5 Share Posted February 5 (edited) May be worth having a look around here: https://www.structuralbasics.com/ https://www.structuralbasics.com/timber-column-design/ There is a reason that beams and columns have different names. Edited February 5 by SteamyTea Link to comment Share on other sites More sharing options...
Gone West Posted February 5 Share Posted February 5 13 hours ago, Russell griffiths said: Why build them into a cassette ? stick build it on site and clad it in osb all on-site. theres 3-4 that have done this i believe. @Gone West and @Patrick We used 350mm portal frames which were made in the factory in two halves for easy transporting. They were joined on site and lifted into position. We used timber I beams for all of the structure, so no solid timber or steel. The whole frame was covered in 15mm OSB3 as racking. I then routed out the openings when the weather improved. Link to comment Share on other sites More sharing options...
Kelvin Posted February 5 Share Posted February 5 (edited) All my windows are framed with plywood. I added that after the fact, which wasn’t easy, once I realised the difficulty I was going to have sealing and taping the windows without a flat surface to fix to. There was one window I didn’t frame (dormer window) and it was a challenge to get the airtight membrane fitted around the frame and then taped for airtightness. I also added the airtightness membrane along the roof/wall junctions before the roof went on. Edited February 5 by Kelvin Link to comment Share on other sites More sharing options...
SteamyTea Posted February 5 Share Posted February 5 11 minutes ago, Gone West said: made in the factory And plenty of polyurethane adhesive. Link to comment Share on other sites More sharing options...
Gone West Posted February 5 Share Posted February 5 4 minutes ago, SteamyTea said: And plenty of polyurethane adhesive. Very true. Link to comment Share on other sites More sharing options...
Norbert Posted February 5 Share Posted February 5 (edited) Eden Insulation in Appleby also use I beams in their cassettes. Panel Construction | Eden Insulation Ltd Edited February 5 by Norbert 1 Link to comment Share on other sites More sharing options...
efkor Posted February 5 Author Share Posted February 5 Thanks very much everyone for your comments. If I hadn't already spent 4 months on getting my SE to produce drawings, I might be looking seriously at switching to the portal frame solution of Gone West. And looking at the impressive i-beam structure from IanR, I can see what is possible. As you say Ian, the connections are just different to the solid wood connections. A good question raised is why I am making cassettes onsite instead of doing a stick build. The reason is connected to the fact that I am a solo builder and I have a 2-storey brick house that I am extending upwards, back and sideways into a 3-storey house. To enjoy the build process, I will fabricate the cassettes precisely in the ground floor "workshop" away from the vagaries of the Cumbrian weather. After creating and storing all the cassettes for the ground floor, I will then enlist a couple of helpers for one day to erect them. Repeat for the other two storeys. And how do I get the cassettes up to those floors? I've bought a used half-ton hoist (£600) and installed it above the (removable) stairway. And moving the cassettes around is achieved with used heavy-duty skates (all my kit is purchased from BPI the online auction site). Consequently, the cassettes will have maybe 4 or 5 times the number of connections that occur in a Gone West or an IanR type structure. On reflection, with all of the extra work required on connections and packing the voids (there lots of 2 and 3-ply also) I think I will go with solid timber and take the hit on thermal efficiency. My wall insulation is 175mm stud plus 40mm EWI and I think the cheaper solid beams will subsidise the cost of the EWI. By the way, Norbert, I left phone messages with Eden Insulation last week and received no reply. I drove to their premises in Appleby this afternoon and the office/workshop was closed up. Maybe they've gone out of business? They have a great product ... I hope that they stick around. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 6 Share Posted February 6 12 hours ago, efkor said: To enjoy the build process, I will fabricate the cassettes precisely in the ground floor "workshop" away from the vagaries of the Cumbrian weather Good man. Once set up I find making repeat items quite relaxing. Link to comment Share on other sites More sharing options...
efkor Posted February 7 Author Share Posted February 7 I totally agree, Steamy Tea. Finding repeat items in a self-build seems a rarity and they should be enjoyed to the full! Link to comment Share on other sites More sharing options...
Norbert Posted February 28 Share Posted February 28 On 05/02/2024 at 18:38, efkor said: By the way, Norbert, I left phone messages with Eden Insulation last week and received no reply. I drove to their premises in Appleby this afternoon and the office/workshop was closed up. Maybe they've gone out of business? They have a great product ... I hope that they stick around. Yes they are still in business and fully booked until the autumn, but the are only a small company, perhaps they were away on site. Link to comment Share on other sites More sharing options...
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