lizzieuk1

We've not got that far yet! Been preparing for ages so info gathering brought us to vacuum glazing. AFAIK there are 2 available, Landvac and Fineo, one has more spacers than the other and a slightly superior u value. When we looked at the landvac in a window at the Homebuilding show it was very hard to see the dots, certainly from a distance they were invisible. Worth popping along to see some in frames if you can. We're yet to decide as really don't want to go for timber sashes, mostly because of air tightness but also due to ongoing maintenance. Finding a supplier for upvc sash with vacuum is proving a challenge, seems far easier to get them in timber though! We are going to look at dummy sashes along with the Quickslide - though Nod has a poor experience of them so we need to be quite critical with viewing them. I believe they now have a rating of 4 for air tightness so wonder if they have refined the design - that will be a question we will certainly ask. Issue is we can't get a 3g sash - which we'd prefer- but can get 3g in the dummy sash so will see how they look. On our last build we used Residence9 3g and they looked very convincing as far as timber look goes - certainly worth a look if you have any non sash & want to consider upvc. Hope that helps!

That's certainly worth thinking about, what would the cold bridging issues be though? I'm wondering if we could add a steel at first floor ceiling that we could take a post up from to support the ridge, do you think that's a viable option?

Thankyou 😊 lots of time spent there so really appreciate that. Re the load transfer, the 3rd floor walls around the landing don't sit directly above the 1st floor walls so, is there an issue there transferring the load down? Also, would we need all those internal walls to be solid, load bearing walls? Currently we were intending to do studs on 1st Floor (except stair wall)

The total span is 14m, we do have internal walls but the walls on the 3rd floor aren't above any supporting walls below.

Really trying to avoid that option, will have to be a compromise somewhere, just trying to find the best one!

We've hit a bit of a stumbling block with this! SE has suggested we will likely need a supported ridge beam (span is 14m) to do the I beam detail, prob is our layout on 3rd floor doesn't have any walls directly above the 1st/2nd floor walls so question then is how to provide ridge support. We also have a rear section of the house to tie in (L shaped design) so wondering how/can that work with I beams 🤔 Anyone know if I beams can be made into an attic truss and be 'self' supporting?

Thanks Iceverge, food for thought then.

Would it be an option to use rockwool slabs between the I joists if we couldn't do the blown cellulose. Looking at thermal values they look very similar. No idea on cost comparison though so, any info on that would be helpful.

Yes we could, and will, work in the drier weather (so long as the uk summer plays ball!) but with a 1.7+m trench in clay I'm not convinced it is any cheaper than the raft. Did a quick high level costing and there was very little difference. Will do a more detailed cost once I hear back from the raft suppliers to see how things compare. It's a nightmare trying to decide as everyone has different preferences and all perfectly viable reasons for those preferences! Will have to make a decision at some point or we'll never get our regs drawings submitted!

Yes, but the upper 400mm is topsoil so easier as less clay to excavate - after digging a large 'pond' out in the field we've experienced the grimness of excavating the clay too 😆

It's a fair point JohnMo but, we feel, as we will likely do much of the works ourselves that, the detail may be simpler to achieve. Also, SE has said on the hedge side we will need 1.7m deep foundation (if medium vcp), with all the usual hassle of clay boards etc, not to mention the sticky mess of excavating all the clay! I think a raft may be a better solution.

Yes, I think you're right, the greenraft looks similar to isoquick- hadn't noticed that last week when I looked at it. Will make contact with AFT and have a chat, need to make sure we start things in the right way, literally the foundations of the project! Thanks Ian!

Is that because Isoquick use a level, constant 200-300mm concrete slab rather than an integrated ring beam Ian? Have had a high level cost from Greenraft for material supply, worth asking them for design?? My worry is the SE doesn't have enough experience and will just design the easiest option, which, inturn will mean its sub-optimal. Don't want to upset the SE but need a diplomatic way to tell him we're going elsewhere for the raft 😬

OK, so the SE has come back to say happy to detail a raft for us. I asked for an example he has done before but, his reply was: "I have done insulation below ground bearing slab for the industrial building working in the previous company and I do not have such a detail. I have been running my company for 6 years and no one from my 1200 projects has done XPS below the slab. It's a shame because this is a correct way to insulate the building. You should assume 200mm XPS if you wish to have a well insulated building." Then he's put a link to Isoquick as an example of a foundation he feels is ideal. Now, we're not suggested he can't design one but, a bit concerned whether it will be the best option. Help! Should we go to one of the raft suppliers or elsewhere to get it designed?