George

Agree piles and cantilever beams the most likely viable solution. Rafts wouldn't be suitable as although they wouldn't damage the sewer, the water company is more concerned about getting access to the sewer in future and they wouldn't want to undermine a raft.

We've moved them for housing estates but not for a single house extension. Essentially it's the same process but the costs are dramatically higher for bigger sewers - they are much deeper! They might go for build-over (cantilevered) but it is not a certainty. Is there any scope to change the floor plan to avoid it?

I haven't really paid much attention to this thread but this jumped out at me. The minimum formation depth for any foundation is 450mm to get below the frost depth. Are you going to insulate the surrounded ground as well as raising the level (this is commonly done in America but not so much here)?

Oversite is a layer of concrete about 50mm thick to cap the soil beneath the suspended floor. Sleeper walls are walls which just support the suspended floor. They may be added to subdivide the spans of the beam and block

It depends what your tolerance for risk and any differential settlement is. You can pour slabs in stages. Connecting them isn't strictly needed for a domestic slab, but is easily done. Drill 10-12mm holes in a plank of wood at 600mm centres and shove 500mm length of reinforcement bar through. One side will get cast in and the other side will stick out read for the next pour. You sometimes have to cut the timber out but it'll work OK. You can even get fancy with slip bonds. But for domestic loading and with some acceptance of differential settlement (or which a build up above the slab) you could just pour them adjacent with no dowels. They should be level though - string lines or lasers are cheap and easy. Compacting with a bucket isn't an accepted method but again, would probably work well enough. Mind you hiring or buying a compactor is pretty cheap and easy so personally I'd try and mechanically compact it.

If they're like me it's because surveying and drawing up floorplans is a bit dull and not the value we add! If I get a set of plans from an architect my profitability and job satisfaction is much higher. I will do it... but begrudgingly so I'd have done the same and suggested an architect in the first instance. But agree overall, there's no reason the engineer can't do it.

Too many variables to say - is it shallow mine workings, a shaft, has it been treated, is the surrounding area made ground. You might be able to get some advice from the Coal Authority as I've always found them to be helpful.

The height is the issue here. Part A building regulations says wall below 2.5m can be 90mm but with piers. So reverting to the general rules H/16 = 2.7/16 = 170mm thickness.

I can't see a way to get a lintel where it needs to be without destabilising the arch in the process. Needle beams and props I think.

There's a reasonable chance there's an arched lintel or tension strap in place. I should get a complete understanding of the existing structure first, that will probably need some intrusive investigations and a visit from a SE (or do you have construction drawings?). I concur with there's a potential can of worms that needs to be dodged. I'd then have detailed discussion with a window supplier. Potentially they could support a aluminium infill panel or glazed infill. The extra cost of this would be somewhat offset by not messing with lintels. Simple fix is to remove the arch and put in a flat lintel but it would be lost a nice feature.

The slab is designed to allow for any settlement that might occur in the subbase. However I've got some ideas based on the 'traditional' no concrete foundation (redeveloped by Frank Lloyd Wright) which I'll sketch up when I'm on my computer.

Although there's significant overlap between manufacturers' products, each manufacture could have slightly different criteria for the use of each lintel. So really you should be checking what you need for each particular use case.

Depends on how on the ball the Lead Local Flood Authority is but you might need to attenuate the outflow with a orifice chamber or hydro brake. Although usually just calling the ditch a 'swale' and the drain a 'overflow measure' will do the trick.

Resin anchors should into the middle of the brick. Mortar can have variable strength and so you might not get the full rated capacity.

Sleeved resin anchors is best for perforated bricks but you can get away with non-sleeved for those. I'd just pay the extra few quid for the sleeve. Agree normal plug and screw is fine for the wall starters. They aren't (supposed) to be subjected to any significant load. Use the sliding type on a rail.