idris Posted December 27, 2023 Share Posted December 27, 2023 Doubtless a silly question for my first on the forum ... I'm researching fitting a SIPs floor onto ground screws but I can't seem to find any indication on fixings. Access to put screws up through the ground screw plate will likely be limited, and screwing down through the SIPs floor into the plate just strikes me as wrong for so many reasons. Or you could sit the building on the ground screws and just hope it doesn't move. Does anyone know what the usual way to do this is? Link to comment Share on other sites More sharing options...
markc Posted December 27, 2023 Share Posted December 27, 2023 Good morning and welcome, no such thing as a silly question. Depending on size, a sips structure will generally need a subframe that would be attached to the ground screws, the panels would then go on top of the sub frame. 1 Link to comment Share on other sites More sharing options...
JohnMo Posted December 27, 2023 Share Posted December 27, 2023 Are you just making life hard for yourself? If you are using ground screws for a good reason. Would you not bolt bearer beams to the ground screw and the the floor panel to the beams. You may be easier Ground screw Bearer beam 22mm floor panels Insulation (floating) either EPS or PIR Floor panels (floating) 1 Link to comment Share on other sites More sharing options...
idris Posted December 27, 2023 Author Share Posted December 27, 2023 What I've seen has made no mention of a subframe, so that's useful to know. Now you say there's no such thing as a silly question but ... how does a frame make fixing the floor panels any different? There's still limited access from below and screwing down has the same issues. I can see at the edge of the structure you could use brackets a little more easily, but I can't picture how that's a big gain. Link to comment Share on other sites More sharing options...
saveasteading Posted December 27, 2023 Share Posted December 27, 2023 Have you a picture of the intended screws? In my mind, and I think those answering before me, you simply build a deck using timber or perhaps galvanised steel. Onto that you can build what you like. Fixings would be from above, screwing down through the top plates of the screws. Big screws or maybe bolts. I'm not a fan of ground screws although I can see they have their place. Temporary structures with difficult access comes to mind. What is it that appeals to you? 1 Link to comment Share on other sites More sharing options...
markc Posted December 27, 2023 Share Posted December 27, 2023 On top of the ground screw you attach a L or U shaped bracket/saddle, these allow you to fix horizontally through the sub frame (or into perimeter frame of a smallish sips floor panel. Link to comment Share on other sites More sharing options...
saveasteading Posted December 27, 2023 Share Posted December 27, 2023 Sips panels and ground screws....sounds like the advice from exhibitors at a self-build exhibition. Link to comment Share on other sites More sharing options...
idris Posted December 27, 2023 Author Share Posted December 27, 2023 These are the type of support brackets I've seen. https://www.groundscrewcentre.co.uk/products.asp?cat=Ground+Screw+Brackets It looks as though the SIPs variants are designed to have floor panels sitting directly on them, as opposed to those designed to take a frame. @saveasteading Your anti-marketing-hype cynicism is admirable, but I can assure you I've never set foot in a self-build exhibition and this is all the product of my own ignorance and misguided online research. But yes, access is a significant consideration. An alternative would be concrete piles, but I'm not convinced that would be much better. Why don't you like ground screws? Link to comment Share on other sites More sharing options...
markc Posted December 27, 2023 Share Posted December 27, 2023 (edited) @idris you have to look at what a SIP is, a block (or several blocks) of polystyrene with a thin ply or OSB glued on either side. The ply or OSB gives very little to screw into. When used as walls they have foot and head timbers for rigidity and you fix through the SIP sheet and into the solid timber. the Sips panel support doesn’t have any fixings, it is just a support to take deflection out of a panel. Edited December 27, 2023 by markc Link to comment Share on other sites More sharing options...
saveasteading Posted December 27, 2023 Share Posted December 27, 2023 34 minutes ago, idris said: Your anti-marketing-hype cynicism is admirable, but I can assure you I've never set foot in a self-build exhibition Apologies. Neither have I , I was only guessing that they will be there. I used to go to Ecobuild though, now named something else, and one year there were several ground screw exhibitors. I took it seriously, but further research showed they were all exaggerating the strength and value many-fold. I think they are used a lot for radio masts etc, as a jcb can drag them up the hill and screw them into the ground. Why don't I like screws? The reps told me untruths and wasted my time. So I'm suspicious of all the information. It has to be just the right ground. Weak enough that normal foundations aren't suitable. Strong enough that the screws will hold. Is it right and proper that I could buy these online without proper knowledge? I expect that traditional footings will normally be better value and durability. I did once build a building on stilts. Concrete pads, then concrete legs up to level, then beam and block floor. Why don't I like Sips? Overpriced. Specified as the 'latest thing' by consultants who don't understand costs. It is just ply and foam at a high cost. They all work and are ok in the right place. Just check the alternatives. Link to comment Share on other sites More sharing options...
idris Posted December 27, 2023 Author Share Posted December 27, 2023 @markc Don't worry - I know what SIPs, how they're constructed and how they fit together. I've just never considered their use in floors, as they are in the kits I've been looking at in the last couple of days. A SIPs wall is anchored to the floor pretty much the same as a timber framed wall - you simply bolt the wall's bottom plate to the whatever is beneath it and screw/nail the rest of the structure to the plate. But that doesn't deal with how a SIPs floor panel is usually anchored to whatever's beneath it. Even if the're faced with 22mm OSB (which I doubt), that's not a lot to screw into. So as far as I can see, especially with those plates, the intention is that the entire structure just sits untethered. @saveasteading I'm pretty sure you can dig a trench and get concrete pumped into it without any proper knowledge too. 🤣 Are SIPs over priced? In some cases, possibly, but for what I'm looking at, having built an insulated framed structure before, the increased cost is far out-weighed by the savings in time and (my or someone else's) labour cost. Link to comment Share on other sites More sharing options...
saveasteading Posted December 27, 2023 Share Posted December 27, 2023 21 minutes ago, idris said: how a SIPs floor panel is usually anchored to whatever's beneath it. A good point. you wouldn't want to be fixing through the foam, which will simply crush. Why not though, fix a solid platform, then infill with foam and additional battens as necessary, then another board on top. It is a diy SIP. Uplift would be interesting with these brackets. A couple of tek screws, as shown, may well suffice, but I would want to check 27 minutes ago, idris said: you can dig a trench and get concrete pumped into it without any proper knowledge too Quite so. But I think even the dimmest builder knows a bit about footings*, but zero about screw piles. Do the building regulations advise on screw piles? *I am reconsidering that, thinking of some previous situations.. A bit isn't necessarily enough. So: your situation: what is the ground condition? Link to comment Share on other sites More sharing options...
Iceverge Posted December 27, 2023 Share Posted December 27, 2023 I like screw piles but they're rarely the cheapest or most durable option. You have to do very little ground disturbance and can easily deal with undulating surfaces. They are dear however. As far as I know you'd need to mount a say 200*75 timber subframe to join the piles together and then drop your sip on top. Run the screws from the top down threading into the 200*75 timbers. If you used pan head screws and didn't do mad with the impact driver the sips should be ok. Here's a video of the subframe. From 3:30. Link to comment Share on other sites More sharing options...
idris Posted December 28, 2023 Author Share Posted December 28, 2023 Interesting build video, not least as I couldn't see any mention of fixings between the frame and the ground screws. Their frame just sits on the ground screw top plates and the flooring panels slot into the frame. The implication is that a strong enough wind could lift the finished building off the ground screws. Link to comment Share on other sites More sharing options...
joe90 Posted December 28, 2023 Share Posted December 28, 2023 4 hours ago, idris said: Interesting build video, not least as I couldn't see any mention of fixings between the frame and the ground screws. Their frame just sits on the ground screw top plates and the flooring panels slot into the frame. The implication is that a strong enough wind could lift the finished building off the ground screws. Yes I noticed that, I would have fixed brackets from the timbers to the part of the top of the screw pile that was showing. Link to comment Share on other sites More sharing options...
idris Posted December 28, 2023 Author Share Posted December 28, 2023 I guess the mitigation is that it's a ******* big "garden room" and it doesn’t get that windy this side of the Yellow Brick Road. Link to comment Share on other sites More sharing options...
joe90 Posted December 28, 2023 Share Posted December 28, 2023 (edited) My worry would be it sliding off the ground screws rather than lifting, I am a bit OCD and tend to over engineer things but for the sake of a few brackets it’s piece of mind. @idris is your building going to be that heavy/big ? I looked into ground screws for a garden room on a 2ft slope so the screws would be longer and make up the height difference and I could screw up into the floor timbers. Edited December 28, 2023 by joe90 Link to comment Share on other sites More sharing options...
saveasteading Posted December 28, 2023 Share Posted December 28, 2023 It absolutely has to be fixed down, and well fixed. Yesterday's news shows what uk wind can do. Extreme gusts can lift and slide a small building. 1 Link to comment Share on other sites More sharing options...
saveasteading Posted December 28, 2023 Share Posted December 28, 2023 Uplift and horizontal forces can be calculated. The manufacturers should have calculated what will work for any UK location and have standard details. Link to comment Share on other sites More sharing options...
joe90 Posted December 28, 2023 Share Posted December 28, 2023 https://www.bbc.co.uk/news/uk-england-manchester-67831843 Worth a few brackets 🤷♂️ Link to comment Share on other sites More sharing options...
Gone West Posted December 28, 2023 Share Posted December 28, 2023 5 hours ago, saveasteading said: Extreme gusts can lift and slide a small building. Very true! Storm Eunice slid our neighbours shed about 500mm off the concrete slab it was sitting on. I've got 22 expanding bolts holding my shed onto the slab. 1 Link to comment Share on other sites More sharing options...
idris Posted January 4 Author Share Posted January 4 In case anyone needs an answer to this in future, having spoken to the lot supplier I'm looking at, this is how it works: The SIPs floor panels are joined by solid timber (rather than the insulated joining pieces I've seen elsewhere) and bearer beams are supplied to sit between the floor panels and the ground screws. The recommendation is to use ground screws with the flat SIPs type top plates and these are sited under the joins on the floor panels. Self tapping tek screws are then driven down adjacent to the panel joints, through the jointing timbers and the bearer beams and into the ground screw top plates. Link to comment Share on other sites More sharing options...
saveasteading Posted January 4 Share Posted January 4 42 minutes ago, idris said: Self tapping tek screws Do they quote any particular spec for the screw? This does need proper calculation, for pullout resistance and for tensile failure. Link to comment Share on other sites More sharing options...
idris Posted January 4 Author Share Posted January 4 There was some mention of size, but I forget what it was. Link to comment Share on other sites More sharing options...
saveasteading Posted January 4 Share Posted January 4 6 minutes ago, idris said: some mention of size Ok. I remain surprised at the vagueness. I wonder if any have blown away this last week. Link to comment Share on other sites More sharing options...
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