Redbeard

Any thoughts, anyone?

This surely depends on the ground conditions? If it is really firm soil then the soil itself will 'shutter', no? Are you looking to avoid 'boundary creep' (or whatever one might call it)? If so, seems there are 2 options: 1. If it's really firm ground: Dig straight and true. Fill. 2. If it's not firm ground: Set up shuttering (N.B. This could well involved excavation on your side in order to ensure solidity - are you 'geared up' for that?): Fill.

I think we need a sketch or drawing, including the insulation detailing in the slab. Assuming the walls to rise from the slab (if not FFL) what stops thermal bridging straight through to the screed, level access or no level access? It sounds as if you need a thermal break, which has not been designed yet. I may have misunderstood, but a pic would be good. Something like Compacfoam (load-bearing insulation) springs to mind, but without a dwg I cannot suggest where or how you place it yet.

My bathroom wash-hand basin waste (which has worked pretty well for the last 2 years with only the odd ‘plunge’) seems to be air-locking. I have had most of it apart and it all seems clear but once I put it back together again it does not run away. The waste pipe currently runs down through the bathroom floor, horizontally along above a false ceiling in the room below and then down the wall a little further via one ‘down’ and one ‘out’ elbow, to the SVP. I don't really know what the problem is that I'm trying to cure, but I wonder whether I could simplify it by running the waste to the short spur of horizontal soil pipe running from the WC to the SVP In the bathroom. I suspect I would also need an AAV, and if so is that OK to go on a T just before the connection to the horizontal soil pipe? Inept sketch attached. Any advice gratefully received.

The (external) doors I want to deal with do not have sufficient clearance to allow me to use self-adhesive D/S, so I need something with a 'ground' which either tack or screws on. I prefer the screw-on variety as they tend to have oval holes, allowing you to 'nip them up' with the d/strip touching the door, then you can tap to adjust of the door is at all bent. Many options come with a brush-pile or semi-rigid rubber d/s. I would prefer something with more 'give' than the hard rubber and less tendency to leak than the brush pile - say quite 'squidgy' silicone 'rubber'. Any suggestions? Thanks in anticipation.

I wasn't saying it's normal, just that it's not catastrophic. If you paid for a tight job you should have got a tight job. I am not a groundworker but the last footing I set out for a client was less than 3mm out over a 6m diagonal, and was flat as a flat thing all over the top. Perhaps I got that so reasonable because I do not normally do it, and I hate it!

Are the 'foundation-builders' taking on the rest of the build? If so it's only them who will have the irritation of making the necessary adjustments because they have not met your stated tolerances. It'd be a different kettle of fish if they charged you extra because of their shortfall! I guess if it were me I'd be a little concerned about future works if, following assurances, the 1st bit was below par. OTOH if you'd done the footing yourself and it was a bit 'out' you'd just 'suck it up' on 'phase 2'.

Is your sub-floor ventilation really excellent? One side to the other, and nice diagonal paths too? Vents at 225 x 150 minimum and preferably 225 square? I have sadly seen quite a few examples of retrofit UFI where moisture is sat on the underside of the bottom membrane due to insufficient 'scavenging' of moisture-laden air below the 'sandwich'. Don't assume that just because you have breathable membranes and vapour-permeable insulation there cannot be problems. This is not necessarily the case. Like others I am struggling to see how you could get your under-layer of WF under the joists (and fitting tightly together) from above. So would your lay-up, from the bottom, be: 35mm WF, membrane, flexi WF, VCL, floorboards?

It's a tiny point, but that's arguably what the sand blinding is for. I guess no harm having belt and braces!

Out of interest, why 30mm EPS below the DPM?

Where or what is your Vapour Control Layer? The only thing I can see in the right place is If that's a VCL is it taped to within an inch of its life at all joints, penetrations and perimeters?

Is this new-ish render or old? Looks like modern thin-coat, in which case I am surprised it's a metal bead, not plastic. The rust will probably come back eventually, whatever barrier paint you use, and trying to paint over it in render colour may leave the bead exposed. Why not dig out the angle bead and buy a plastic bead and a bag of base-coat render, and then cast around on here for someone with a part-tub of 'gritty top-coat' left. If the colour is not a perfect match you can get some masonry paint to go over.

I imagine the is armoured in some way, and not a PVC-sheathed cable. Just in case any PVC-sheathed cables are involved, remember (a) that polystyrene (expanded or extruded) leaches the plasticisers out of PVC cable sheathing (symptoms include PS insulation 'glued' to the cable) and (b) that cables (particularly 'grunty' cables, whatever they are sheathed in) are not meant to be 'tucked up warm' in insulation.

Even when I have been doing stuff on a Building Notice I have had to provide SE calcs for lintels, footing pits etc. Likewise they can require wired linked smoke alarms (which in my particular case have been a PITA) and will ask you to answer requests for fire rating details. I have found, since the 2022 regs, that some BCOs are not 100% sure what they need to be asking for. I was asked re surface spread of flame for rigid wood-fibre-board with 8-10mm plaster on. I Q'd it and they withdrew that request, acknowledging that the board was completely covered, with approx 30 min fire resistance in the plaster. I agree wholeheartedly, though, that checking is important. I used to get a bit fed up when BCOs did *not* check and ask Qs re my work.

Good to hear that. Sadly the company I used to use had a 'no foreign sales' policy as soon as we left the EU. If you bought abroad who did you use, if I may ask?