tonyshouse

Go for the best you can now, I would aim lower on the roof for sure, good workmanship is crucial, I like fitting joist or rafter, then insulation then the next one etc what is your air tightness target?

Good idea to think it all through before you start, try to make all decisions while the pressure is off, write down a wish list mine would include low energy demand, U value 0.1 or lower, 3g, MVHR, wetroom style, no tiles, low maintenance, sustainable, solar, heavyweight construction for max comfort, ....

Chances are that it is very draughty under the floor with outdoor air blowing through your underfloor second floo floor void ? then some of the insulation could be thermally bypassed, missing or poorly installed. Do you have any pics from when it was being built how about a thermal imaging survey to highlight problem areas.

The important thing is the insulation in the cavity, not bridging it. The lintel itself is all but irrelevant, an I beam web could be insulated a bit. A “normal‘ lintel Introduces rotten thermal bridges. These can with good design (check lintels etc) be mitigated. i used separate lintels on my inside and outside skins and designed out thermal bridging. what are you thinking about this for?

Option 2

Because the sole plate sits on cold foundations or slab, with a chunk of wood on top of it, there is then a double thermal bridge there and it will most likely be the coldest place the house so condensation will Collect there, it can’t soak into the dpc or move through it then if mould forms it will be followed by decay

I would start with your target U value and think about how you will mitigate thermal dredging, typically very high condensation risks on top of the dpc in cold conditions

How will you ensure no draughts from outside get into the void?

A geed bricklayer can lay 1000 per day, reckon on 800 add a couple of days for scaffold and a couple more for weather and floppage

In airtightness terms I like to have a full air barrier above the plasterboard, so poly sheet first then plasterboard etc cant see how air tightness could possibly work with plates first?

Insulation above is poor! When I build roofs I go roof structure, fascias, tack, lighting wiring, insulate, (dead easy to perfectly at this stage including over the wall plate area), felt, batten and tile ?

+1 ceiling first, some noggins where Walls parallel to trusses nails for to fix everything

Is it tongue and grooved? What is the length of your tongue and how far in does it go? Is it tongues up or grooves up? what is the bottom detail?

I kept my salt box outdoors for 15 yrs when it was separate, it did freeze and break the valve once though

Is it up to pressure on the sealed water side? has the gas been purged

Cheap one and do it at night, 39 quid kitchen cube type laser one will do it

I am, beam and block does and so do suspended floors

All it makes me think of is an in house winter cooling system

Can you open them up a bit, I was doing 100 cavities in the 1980’s — insulation is cheap at this stage compared to heating bills.

I worked on blockwork and insulation and ensuring no mistakes try for discount on batts or go to a specialist insulation supplier. is price for beads for your wide cavities?

I too like fully bonded, a must for load bearing, strangely insurers and bodies seem to say don’t bond in partitions. I didn’t bother with an an insurance backed guarantee and bonded in all my walls. No issues and I am past the ten year mark and thousands of pounds richer.

If they freeze when wet they die. It is not easy to lay wide blocks properly. I like a below dpc route for water to drain away by. They are widely used - not for me though

Yes, dead naff. It causes a lot of thermal bypass if outdoor air can get in between the walls and linings. Draughts come out everywhere, you loose the thermal buffering of the masonry.

I went full fill batts but 300mm wide cavity. No way would I let brickies install it, I did it all myself. They did try to fit some but I took it out and re did it. beads are great but I think you will find they work out too expensive. If you do for them go for platinum ones.

I use recycled aggregate Medium density blocks