Conservatory Floor

[UncleLumpy]

I'm about to add a 3m x 4m conservatory on to the back of my house which requires a 600mm high dwarf wall. Can anyone abswer the following questions for me?

1. Will 650mm foundations be OK or should I go down 1m?

2. Should I finish the foundations below the existing ground level and build up with 2 courses of engineering bricks and will these be fine as a damp course or should I add a DPM, if so where should it go.

3. Must the finished floor height be level with the existing damp course? If it can be lower, does it matter how much?

4. I've been advised that the floor should be 75mm hard core then 100mm concrete with a screed on top. Is this OK and where should the DPM go?

5. If I decide to put in under-floor heating, I'm told I should allow for 50mm of ploystyrene installation on top of the concrete and then a 75mm screed on top of the ploystyrene. Is this OK and what material should the floor screed be.

I know I really should call in a builder but I fancy having a go myself, just for the experience.

Thanks in advance.

 

[noseall]

[quote="UncleLumpy"

1. Will 650mm foundations be OK or should I go down 1m?

if the ground seems pretty solid at this level (650mm) then yes.

2. Should I finish the foundations below the existing ground level and build up with 2 courses of engineering bricks and will these be fine as a damp course or should I add a DPM, if so where should it go.

we like to finish a mass filled footing no more than 450mm or six courses down from dpc. this at least gives room to site any drainage gulleys close to the building. use engineering bricks or 7n dense solid blocks below dpc which should be at finished internal floor level.

3. Must the finished floor height be level with the existing damp course? If it can be lower, does it matter how much?

it is better to have floor levels the same throughout, but you can have a step down if you like, or if external ground levels permit. your dpc will correspond with your floor level, but should always finish at least 150mm up from external ground level.

4. I've been advised that the floor should be 75mm hard core then 100mm concrete with a screed on top. Is this OK and where should the DPM go?

floor should be, 100mm compacted hard core, 30-50mm sand blinding, 1200g dpm, insulation layer, 100mm floor slab and 75mm screed. you can steel float the concrete slab if you want to omit the screed.

5. If I decide to put in under-floor heating, I'm told I should allow for 50mm of ploystyrene installation on top of the concrete and then a 75mm screed on top of the ploystyrene. Is this OK and what material should the floor screed be.

as above. use sharp sand,(grit sand, screed sand, concrete sand) for the screed.


I know I really should call in a builder but I fancy having a go myself, just for the experience.

Thanks in advance.[/quote]

 

[UncleLumpy]

Noseall - Many thanks for that.

 

[masona]

This may give you some idea

http://www.hollinsheads.com/blog/stages.html

http://www.windowquote.co.uk/build-a-conservatory.htm

 

[joeb99]

How deep should the foundations be if the extention is a single story instead of a dwalf wall?

 

[noseall]

How deep should the foundations be if the extention is a single story instead of a dwalf wall?

if you are building an extension under building regulations then 1m below external ground level, unless ground conditions dictate otherwise.