George

Yeah - the calculations just include their 'standard' loading that may or may not be used. On sheet 7 the actual loading in used in the beam design are listed - none of those are beam & block or first floor. Only roof and 350mm of blockwork. The 7.28kN/m & the 5.9kN/m follow through to the calculation in the pdf.

I don't think they have. In the summation there is only 350mm of block. I agree with @Gus Potter that things could have been made tighter but based on the information in the thread, it's not as though the SE has gone completely wild. Builders always say beams are oversized. A lower depth beam with the same stiffness would have required an even heavier beam - this would be more steel weight and potentially splice designs etc. So from the SE's perspective, more cost to him. The most common competing interests are weight/cost (all things being equal a deeper beam is lighter), depth of beam and speed (allow for over-deign based on limited information). In the absence of other instructions the SE went with cost

Agreed - the model that works in my head is that the EPS is just replacing the sub-base so you still need to allow for sub-soil settlement. Even though the EPS has considerable mechanical strength itself, unless it is laid in a proper manner (interlocking blocks and suitable bearing locations) you're fundamentally still relying on the concrete to provide structural support.

Possibly the lintel or the bay has moved a bit.

What part of the country are you in?

A structural slab is a raft if it's carrying the walls..

If you pay for the ground investigation, site prep, pile rig to get to site, set up and do some piles, the extra cost to do more piles is not great. You should be able to make a pile supported raft slightly more efficient than a normal raft, too. Overall it'll cost more but shouldn't be dramatic, especially per sqm if you are able to make it bigger.

You should either go for a fully insulated raft or a screed on top of insulation on top of the raft. If you don't want sand+cement screed (which is essentially a fine aggregate concrete) you should still be OK to go for a 75mm thick concrete, espcially if using 10mm aggregate. You could even go and find some interesting aggregates to add in. I'm not sure why you were advised 150mm minimum - unless they were thinking of the structural raft below.

Yeah the external projection is enough as it is a reasonable assumption the wall is placed centrally. So overall foundation width is projection x2 + wall thickness. Your engineer will be able to cross check this with ground conditions to get an allowable line load. It isn't an exact science but without full ground investigation, that is how a lot of domestic foundation work is.

If the soil is good then width is more relevant than depth. It's clearly got a proper foundation so you will probably be able to reuse it. But get it inspected.

Steel fabricators and/or the builder really should be taking site measurements prior to fabrication. Ditto with the timber frame fabrication. There are a couple of fixes - either needs to be properly approved by the design engineer, the steel extended (site welded if necessary), or the wall altered. Or a combination of these options. I would imagine that the engineer would say it's OK but you need that confirmation from them. This would be acceptable remotely if they have a full understanding of the issue (photos and written record).

You should ask the engineer who specified the steel. The building regulations are not so prescriptive, however NHBC guidance does specify a minimum of 100mm for steelworks bearing lengths and it is a reasonable rule of thumb https://nhbc-standards.co.uk/6-superstructure-excluding-roofs/6-5-steelwork/6-5-4-installation-and-support/ I would have more concern that the wall is being loaded eccentrically but again this would need the engineer to confirm it is OK.

I was thinking you could either send it outdoors or you could run the 110mm pipe parallel to the joists.

Swap the sink and toilet positions.

Can it go through one of the walls or straight through the floor? If it's a utility or out of sight area, it could run at ceiling height and be boxed out. Bathrooms are often designed around the SVP & toilet - sink & bath/shower drains are a little more flexibility but still needs careful thought.

No, unless they were hospitalised. The bar is quite high: https://www.hse.gov.uk/riddor/reportable-incidents.htm

CDM is criminal law and not civil law so it isn't directly applicable But I agree... unless the client purposefully misled the contractor that the electricity was off and tricked their own control measures to check the electricity was off, I'm not sure how anyone but the contractor is responsible. Does a 240V shock leave long lasting damage?

A mile may as well be a lightyear when it comes to UK geology. Speak to a SE - get them to advise on what geotechnical information is needed (risk of going straight to a GI company is you get overspec investigations). They may charge a few hundred quid to write a spec but they don't need to do a full structural design to know what ground info they will need. Then get the ground investigation done up front. It'll pay for itself - the same information will help on the foundation design with or without a basement. This will then help by either reducing the grounds works required, and/or avoiding abortive work early in the project, and/or de-risking the groundwork for the contractor when they price. I always always advise that for new builds, get a GI done nice and early.

Sounds like a job for a structural engineer.

Obviously only very minimal info there but that is a bit of a stretch for Class Q imo.

Depends on the type. Some are fully built into the inner leaf and are galvanized. They wouldn't need one. If it's a type which is against the outer leaf then may need it. If its an off the shelf Ancon one then just phone their tech support.

Not usually done on domestic scale works. Check the KORE slab specifications, it may be a requirement of the warranty. A plate load test puts a known plate size with a known load and measures the deflection. This can give good, site specific information on the ground bearing capacity.

It used to be that if you put in a giant beam you could forgo the engineer. But Building Control have pretty much defaulted to needing calculations for all structural alterations. However, with the calculations taking into account the actual loading and more accurately determining the deflection, the engineers fees *should* be offset by the reduced weight of steel needed.

I haven't looked a the updated standard but my view was the preferred approach for new build was to prevent ingress with both Type A & Type B waterproofing.