jayc89

What's on the external face of the wall? Render etc? I guess you're going for the "warm batten" method - the idea of the insulation taped tight against the wall is to form an impervious barrier. If there was ever any moisture build up behind the insulation, you'll end up with mould on that wallpaper and no access to it. I'd be inclined to knock it all off it back to brick and gain a few cm extra in the process.

Assuming I'm using this calculator correctly - https://www.changeplan.co.uk/u_value_calculator.php Without a perimeter strip the wall construction would be around 0.19 W/mK and with a 25mm PIR perimeter strip it reaches 0.16 W/mK

What's the reasoning behind dropping the XPS? I thought the introduction of Thermalite blocks, plus the full fill cavity would negate the need for a perimeter strip, is that not the case? (I did plan to include a perimeter strip where the screed joins the (currently external) original property's wall.

Just leaving a 100mm lap on the DPC to tape onto?

I guess a consequence of putting the DPM above the slab would be having the DPM exposed during construction and it almost certainly being compromised.

Tie locations is a good shout. Why put the DPM on top of the slab? I generally thought it was a good idea to keep the slab on the dry side.

Looking at the cavity/floor detail for our extension. A few points for context; Existing house does not have any DPC Existing floor level is just below ground floor level, by approx 50mm, (and surprisingly, given the lack of DPC, has no damp...) Some of the final room layouts will span both the existing and extension floor space. We're aiming for a sensible design, but not necessarily Passivhaus criteria, so are trying to follow the Golcar detail as near as possible. This is what we've come up with; Ideally we'd have gone for insulation under the slab and UFH ran through the slab, not needing screed at all, but because some of the UFH loops need to span both the existing and extension floor space and we won't knock the existing walls down until the extension's water-tight, I'm not sure that would be possible. The extension's final floor level is to remain at the same height as the existing final floor level, so we'd end up with some funky DPC set up for the extension detail we choose. Does the proposed look sensible? Would you recommend any changes?

I can't help, but had a similar experience. Had a survey done as part of the house purchase, was told there was a septic tank just off the rear corner of the house, with images/videos to show it. We ended up having to lay a new water pipe which ran right around that corner and down to the garage/garden supply. We never did find said septic tank. I'm sure we have one somewhere, but I do question the accuracy of some of these surveys. I'm dreading digging the foundations for our extension, no doubt that's when we'll find it Hope you get sorted!

One heating engineer we spoke with recommended to install new radiators on the wall to the side of a room's door as that space is used to get in/out of a room it's unlikely to ever be blocked by furniture etc.

Yep, no blocks are loose when walking on it, just gaps showing between the beam and blocks. I'll brush some around before laying the DPM, just to be sure.

I've started to prep the area and noticed gaps between the beams and blocks. It was previously grouted by the builder who fitted it but I guess some has come loose. Should I attempt to re-grout it? What's the best approach; wet it again and then brush over a dry sand/cement mix?

Makes sense. As soon as the technical drawings are ready I'll be putting the materials out to tender, we have plenty of space to store stuff which will hopefully put us in a better position to take advantage of any delays/cancelations on other jobs.

That's the fine balance I'm trying to strike. I don't want to waste peoples time until the foundations are in, or at least we know when they will be in, but equally we want to get someone booked in as soon as feasibly possible because we know all the good trades get booked up quickly.

Planning permission's in, all being well we plan/hope to break ground in March, once the worst of winter's over. I'll be doing the groundworks myself, along with a couple of friends, but I want to get the professionals in for the brick and block work, as that's probably a DIY stretch too far. I have a couple of well known, local, brickies lined up to get a price from once we get the planning permission back, is there anyone on here who can recommend any other brickes in the East Yorkshire area that I should also contact? Thanks!

thanks @Iceverge I really like the flow of light from the boot room into the kitchen. I’ll suggest that to our architect. I'm not so sure on the side lights in the study though. Given it is a period House the interior won’t be ultra modern so I worry the sidelights might just look a little too office-y for the property?

I think you’re looking at an older drawing. I pretty much agree with all your points and the majority of them are addressed in the latest drawing on this thread. The stairs have two quarter landings so we don’t have the height to get a full size door through to the kitchen there. The current space to the side of stair case was a bathroom on the first quarter landing that we’ve already removed. As it was a bit pointless being there and it gives us the space to expand the hallway into the kitchen, without going through the living room/dining room.

You’re telling me. I can spend hours trying to get a plan right and the architect seems to be able to do it in a few minutes. Clearly it’s not the trade for me! ? That south window faces along the drive (approx 3.5m wide at that point). Directly opposite is a 4ft boundary wall and 8ft of hedges at the other side. So it does let in light, but not vast amounts. The new southerly windows in the extension at further set back from our boundary so should let in significantly more light. We pretty much exclusively use the back door, in fact it’s a bit of a faff when we get deliveries to the front. Anyone who comes to the house, that we’re expecting, knows to use the rear.

Access would be a problem, we'd need a pump too, which becomes expensive for such a small space.

It kinda becomes a moral decision then. Overlaying UFH on the existing screed is very likely to provide poor performance BUT, I suspect it would be the cheapest option.

That's right, a proper screed ("snow ball test" consistency) with UFH pipes in it. Given I only need ~ 0.5 m3, I can't really get it delivered in a ready mix - what's the best way of mixing it up?

Yeah it's a bit of a pain - I should have had it screeded at the same time as the rest of the house, but I had a basement and block and beam floor install to deal with first. I have a small 240v mixer at home, but was planning on hiring one of these for the day - https://www.hirestation.co.uk/tool-hire/Concrete/Cement-Mixer-Hire/070025/ - should get the stuff mixed in a couple of loads.

I dug out our full house (10m x 11m) approx 30 ton came out. It was my first "proper" DIY job so pretty taunting, but as has been said above, it's quite straight forward. The one "gotcha" that caught me out - I was using a laser level to chalk lines on the wall for where the MOT/Sand/Conc was to be filled to and ended up with low points in the middle of the rooms - if I was to do it again, I'd still use a laser level on my datum point, but grab a broom handle, mark the correct depth on it and use it to spot check various points around the rooms to make sure I'm at the correct level everywhere. I suspect you'd end up with a far better finish if you dig out.

I need approx 250kg of cement to mix up some screed. Are there any cheaper options than buying 10x 25kg bags (at ~ £5.92 a bag)?

When we needed to dig out for a new conc slab in our house, I ended up hiring a micro digger and tracked hi-tip dumper; https://www.fairfaxplanthire.co.uk/uploads/file/Kubota U10-3 ZTS Mini Excavator Specifications.pdf https://www.fairfaxplanthire.co.uk/uploads/file/tracked-dumpers/JCB/HTD-5/DUMT0650-JCB-Spec-Sheet.pdf Managed to shift about 30 ton in a couple of days (most of that time was spent getting the bloody dumper in and out of the house!)

What’s the best way to drop the boiler return temp? Buffer tank, or something, between the boiler flow and the UFH mixer? Given I have 550m which will soon turn into 1150m and 16mm PEX carries approx 0.113 l/m (130l in total), I guess any tank would need to be reasonably big?