Mr Punter

Is the rest of the lean-to coming down?

Before you do anything, tidy up the site!

Leca is one I have heard of.

When I have had a project with sprinklers I have the system professionally designed, specified and installed. You will need a tank and pump. The tank will be 1 - 1.5m3. The mist systems may allow a smaller tank but they are more expensive.

I thought oil tanks were bunded?

You may be able to use some sort of geomesh system to prevent erosion and stabilise the bank.

The fire rated ones are £23.30 each, the non fire rated are £11.60 ex VAT. Cut them on a sliding chop saw. Get some nice meaty galvanised fixing lugs. With some windows these twist fit into the frame. Ask your window people what they recommend. God knows how to fit those cranked eaves windows. Make sure you have allowed for the gutter and downpipes either side.

Before you pumped it out, was the water the same level as the gravel pit lake?

It will still need foundations and sub structure blockwork. What is the outer finish? If it is brick or render, you may as well just go conventional construction.

Why not just use standard 200mm cavity closers? There is a choice of PIR and mineral wool insulation ones. They close the cavity, stopping your blown insulation escaping, prevent thermal bridging and stop any rainwater tracking past. Some stainless straps to the inner leaf of block to secure the windows.

I had a customer put solar panels on a 5 degree mono pitch roof which was North facing. This was in Sussex. Apparently the efficiency was not too badly affected.

MVHR is all about ventilation - providing fresh air to occupants and extracting stale moist air. I don't see that this is appropriate for a garage. You will also need to run your unit harder to get it to cover the garage and if the garage is not heated you will need to have the ducting insulated.

In England there is an optional requirement where you need step free access to any connected outdoor space on the entrance storey but otherwise it is the front door only.

Forget the MVHR in the garage. A complete waste of ducting and the system. I had an insulated roof put on an unheated garage a couple of years ago and it stopped all condensation. They came in large plastisol sandwich sheets with 40mm pir. Single garage was £1600 plus VAT all in including removal and disposal of the old asbestos. Mine came from these people http://www.icroofing.co.uk/ There must be someone similar down your way.

I think the PIR is a really good solution. You could fix strips of 25 x 38mm batten to the sides of the rafters to maintain your airflow gap. You could use further short pieces under to hold the PIR firmly in place. 40mm PIR is easy to cut but quite rigid.

The downpipe is already discharging into the grid at the end of the channel. You could direct the flow a bit better.

Internal type C drained cavity membrane with sump and pump will work 100%. You will lose a bit of internal space but it will be completely dry.

It is a pain to work with, very expensive, heavy, not mould resistant, the FST skim is useless, your sparky and dry liners will hate you, but otherwise it is average.

No big deal if you just have some cupboards on the island. If you want a hob or sink you will need services. It is worth extending the electric ring main to underneath anyway.

Most of the dry ridge systems will work fine. You can often re-use the existing mortar bedded tiles if you can get hold of a few spares to replace broken ones. You just screw battens to the top of the ridge to get to the required height and use this for the fixings for the ridge tiles. Easier than messing with mortar. https://redland.co.uk/products/components/ridge-systems/continuous-ridge-system

Can you add some timbers for the overhang on the top of the roof joists so they line up with the top of the insulation, so 120mm insulation and 120mm overhand pieces? Then bring the wall finish up to meet them. You will need to insulate around the timber outrigger pieces.

Aerated blocks are more prone to crumble and not good for fixing to or plastering. Medium density aggregate blocks are good allrounders but you lose a bit of insulation. It may make no difference to the bed reinforcement requirement but best to check with the SE.

The issue is that your floor level should be at least 150mm above the external ground level. It looks like it is the opposite. Also the ground level banks up from this. You effectively have a semi basement without proper waterproofing. If you are concerned whether the patio slab is providing support to the wall, dig a trial pit on both the outside and the inside. You could also gauge the water table from this. I once had a house with a cellar with a screed floor over a DPM and during intense rain water would force its way up between the floor and wall. We dug a sump and installed a pump and accepted that the floor would sometimes be wet. A proper membrane system would have cured it.

I did not even look at this from a b.regs point. You may need sprinklers throughout and enhanced smoke detector coverage. I have also seen automatic fire curtains specified.

I have not done one of these. It may be useful to look at other approved planning applications and see what information they have included.