Mr Punter

NHBC, TRADA and others recommend treated timber for external wall studs and sole plates. I guess it is extra protection against rot if they get wet. For some reason it does not apply to roof timbers. Are your timber I beam flanges treated? Again, NHBC say they should be.

I think the bearing for the soleplate must be at least as wide, so you may need blocks laid flat underneath a spanning the cavity onto eps / screed will mean the bearing would not have an even loadbearing capacity and the soleplate will not be properly supported. The soleplate should be treated timber.

Building regs are being used to improve the energy efficiency standards of new buildings. The standards for Part L, which deals with this, have become far more ambitious compared to all the other approved docs, so what worked 5 years ago will not pass now.

5 minutes is OK. Depending on temperature you could leave it mixing for an hour or two.

Do bear in mind that with trees in proximity to foundations, the actual size of tree is not taken into account, as the effect on the foundation is calculated as if the tree is fully mature. The tree size is only used if the tree is being removed, as it may lead to clay heave. Sometimes Building Control will ask for further information before they give a conditional or unconditional approval. As others have said, don't complain as you will gain nothing and may risk pissing them off.

I think it would end up a right mess.

No but it does apparently help the mortar heal small cracks over its lifetime.

Not really. Most lenders will give a mortgage on the strength of a Professional Consultant Certificate. I have used them for flat conversions, where NHBC were just wildly expensive (like £8k per flat). Everyone was able to obtain a mortgage with no issues.

We have all the stuff in a sliding door wardrobe in the back corner. We have consumer units x 2, 14 no. CAT5 terminated into patch panels flush mounted in the plasterboard, 16 port fanless switch, broadband modem, Unifi AP, phone master, TV cables, TV distribution and door entry control box and it takes up very little room. I prefer not to have a cupboard just for this. Nothing gets too hot so we have clothes etc in there too.

The water will do it no harm. Concrete cures very well under water.

Those solid barrow tyres are useless unless you are on smooth paved ground. Anything else they just bury themselves and unset the barrow if you go over uneven stuff.

I am not sure what the right angle is for. I would have 2 straight runs - 1 from utility to manhole - picking up the WC en route and 1 from kitchen to manhole. I would want access to the start of each run for rodding / jetting. This means you will not need an inspection chamber in the kitchen and the runs will be a fair bit shorter.

No, you unroll DPC straight on the top of the sub structure blockwork and beams on top. No mortar.

Corian is softer than the quartz based materials like Silestone. It is not scratch resistant but you can polish scratches out. It also tends to mark so if, for example, you are preparing strawberries on it you will be left with marks that cannot be wiped off. You will need a scotchbrite and cream cleaner. The solid colours can be joined seamlessly. I prefer quartz as it in non-permeable and scratch resistant. Just don't put hot pans on it.

Oil is only for engineering bricks - especially blues.

300mm thick is fine for domestic up to 3 storey and the 1m depth is often just frost protection / rule of thumb but if you have point loads from columns you may need thicker / wider and / or rebar. Your SE should advise. We have had to do 1000 x 1000 x 400d concrete pads for some columns.

I still don't understand the issue. Is this an existing house you bought? Why did you get the tests done? What do you want to achieve?

Can you just fix some brackets onto the wall at the top with screws and rawlplugs, then screw into the side of the stud to hold it firm? https://www.screwfix.com/p/sabrefix-heavy-duty-angle-brackets-galvanised-60-x-50mm-10-pack/61576

Often have more than one engineer. Sometimes piling and ground beams, masonry, timber frame and balconies can each have input from different engineers.

What is the issue you have? Is it cold, damp, mouldy, high heating costs etc? The detailing of insulation / DPC / DPM gas membrane / insulation junctions can take many forms and there is not always a right or wrong, but some can be better than others. Because the house is complete any remedy suggested can only be applied to the as built, not to how it may have been better in the first place.

I like the Gridshell building at the Weald and Downland Open Air Museum. Should not take you too long to design something similar for your client's granny annex... http://www.fourthdoor.co.uk/unstructured/unstructured_06/gridshell_photo_essay.php

I prefer hydrated lime to plasticiser.

It is tricky to do setting out manually if you have a sloping site, different levels or steps in foundations. If the plan is straightforward and the site is flat then no need for a Total Station bod.

I would look at https://www.screwfix.com/p/timbascrew-wafer-timber-screws-gold-6-7-x-200mm-50-pack/6787j . 50p each, wafer head and you will get 50mm embedment into the OSB / joist which will be plenty. Can you check from underneath to make sure the fixings are locating OK? It is quite easy to miss a 45mm wide target especially if you are butting board edges over a joist. It may be better not to line up the boards with the joists - just lay in staggered rows and screws along each joist.

Agree with @Russell griffiths to get a surveyor with a total station. After the ground beams were in ours did all the soil pipes, wind posts and steel column base plates, as well as walls. Marked with a Hilti pin on the concrete and coloured with spray. I still like to use a tape as a sanity check sometimes.