Foundation depths on conservstory with timber stud dwarf wall

[arcon5]

How deep do you guys suggest for a concrete base so site a conservatory that is sitting on stud dwarf wall? For both the floor and also for the outside foundation as I'm building up with foundation blocks to create a retaining wall first then building up the
inner floor.

It's on a decline/slope. Projection is 3m, with 4.7m.
Height difference from house to roughly 20cm.
Currently block paving.

If I use 5cm hardcore. 1cm sharp sand compacted. Then would 5cm concrete be enough to then start building up the 3 layers of foundation blocks. And I would backfill the rest of the trench the blocks started in up to ground level.

As for the floor I can utilise existing hardcore to make the area flat. Then 2cm sharp sand, DPM, 50mm insulation then 5cm concrete... would that be suitable or can I go less for the inside bit? As that's then a 12cm base plus the hardcore which i estimate would vary from about 6cm towards the house to about 16cm as it gets to the foundation wall with it being on the gradient....

 

[Scarlet Pimpernel]

Your suggestions don't make much sense.
You don't use hardcore or sand for a foundation for a wall.

50mm of concrete is not sufficient for a foundation for a wall.

Depth of trench depends on local conditions.

You don't use sharp sand for blinding for a floor slab.

50mm insulation is not sufficient floor insulation.

50mm concrete is not sufficient for a floor slab.

I don't know if conservatories are subject to Building regulations, but your suggestions would not be sufficient for Building Regs.

 

[arcon5]

No they are not subject to BRs.

So what depths would you recommend for the foundation and floor slab?
I got some of the numbers from a summer house group since my wall is a stud wall so not carrying the weight of a thousand bricks.

So the foundation wall doesnt need compacted mot under it?

 

[Scarlet Pimpernel]

No they are not subject to BRs.

So what depths would you recommend for the foundation and floor slab?
I got some of the numbers from a summer house group since my wall is a stud wall so not carrying the weight of a thousand bricks.

So the foundation wall doesnt need compacted mot under it?

Your local summer house group might be going for economy as the highest priority.
For the foundations, some knowledge of local conditions would help, and I'm not familiar with your local conditions.
As a guess, I'd have thought 600mm minimum depth with at least 150mm thickness of concrete. You can do strip foundations and build up with blocks, or trench fill with concrete. Whichever, no hardcore.

For the floor slab, bearing in mind that many conservatories eventually get converted to full living space, I'd go for 150mm hardcore, 50mm soft sand blinding, dpm, 100mm insulation, and 100mm concrete. Then possibly screed, depending on the finish of the concrete.
Your local conditions might determine something different.

Alternatively, many conservatories become glorified drying or storage spaces.
Only you can decide how yours might transpire.

You could consider wet ufh pipes, with the option of adding/connecting the rest to the system at a later date. But as a conservatory, it must remain separate from the main house controls.