Mr Punter

The room.

As long as it is less than 50% of floor area it is OK, so a feature wall, not the whole room.

The intumescent clear coatings are v. expensive and I am not sure you will get the finish you want. Unless you have a high percentage of the ply, don't worry about surface flame spread. Feature wall is OK.

I would suggest the brick pattern is much easier to have running horizontal. Work out where your cuts will go so that you don't have little slithers of tile. You may need tile trim for the exposed edge by the window.

I think tiling the roof will be more of a challenge! If you are doing vertical cladding as shown you will need vertical battens fixed to the timber frame, then horizontal battens fixed to the vertical. I did some 25mm x 50mm horizontal battens on a radius of 3800mm. I soaked the battens and pre-bent them. They were for render board finish.

Were they not clearly marked out with plastic tape stapled to the breather paper? I can't think of many contractors who would undertake this. Is it just the one elevation or the whole thing?

I would go for 30mm inside the blockwork, fixed with straps. Gives them something solid to sit on and pack out from. We have some IdealCombi windows and they are about 130mm deep, so the glazing should be well within the insulation. @romario how are you fixing your battens for the timber cladding? 150mm plus batten thickness is a sizeable fixing.

It is OK to have inert rubble under the suspended floor. Make sure it is OK with the piling contractor as they sometimes need special support for larger rigs. If there is any topsoil I would remove it.

Just a thought I wonder if this would work with engineered timber like LVL or Glulam instead of steel. You could leave it exposed.

Yes, not wet or sticky, just set. The idea is that the concrete should take longer to dry, which makes it stronger. Check it a few hours after it is poured and tamped.

It works out as 1.8 watts for each degree of temperature difference, so assume the average difference is 10 degrees, your poorer U value would lose 18 watts. Over a year that would be 158kWh, which will probably cost between £8 and £20 depending on fuel type.

Below ground drainage is fairly simple and can easily be DIY with plastic pipe and chambers. Let building control look at the design and see if they have any comments.

Can you post an elevation or even better a Sketch Up showing the gable, just for my own interest? Also, how are the 100 x 100 posts supported? With one it looks like the stairs are in the way. Lots of stairs btw.

Cover the concrete with plastic as soon as you are able, so that it cures properly and you do not get surface dusting.

Get someone to help. It is hard work for 1 person.

@SarahW can you post some pics during and after installation?

It is a very odd configuration. I assume there is some compelling aesthetic reason not to have all the rear rafters at 16.2 deg? As is, there are some horrible junctions and we are only looking at 4 rafters. Bear in mind that the timber may shrink by 15%, so if you have 50mm one side and 150 the other, the shallow pitch may end up 15mm lower. Can you modify the steel?

With brick and block you may get 0.12 - 0.13 with rigid insulation, insulated plasterboard and lightweight block inner leaf.

Fairly simple to DIY. Quick too if the units are assembled. As you have worked out, if the worktop is to be joined with a masons mitre and bolted underneath it is best done with a jig. Cutting down and fitting end fillets and corner fillets takes a while but if they are well done make the job look professional.

If there is a sawmill anywhere near you could ask them for a price to do this as it is a fair bit of material. I am not sure that larch is particularly durable. Is it treated?

7.3 newton concrete block is best for impact resistance. Bet you sympathise with full time brickies now you have tried it!

You may be able to request a bigger meter but they often charge a higher standing charge because they are not so good at recording low flow rates apparently. We have a 50mm meter for fire sprinklers, just to establish there are no leaks and we are not nicking water. No standing charge for fire only supplies. We had a fitting go and the volume of water was epic!

The steps are a fair bit of work and also a security issue. It would be simpler without.

On blockwork, yes. On carrier boards we used Weber LAC and mesh. About 4mm total, sponge finish and painted. Very sticky but finishes OK. Don't get it on your car seats!

Make sure you have really good access to the unit. I loft mounted a Vent Axia Kinetic Sentinel Plus and the only way to get at the filters is to disconnect some of the hoses and commando crawl to the far end of the unit. I doubt the new owners have ever cleaned the filters. It was a struggle for me to do.