Footings / ground work steps, what are they?

[Noah1234]

Hi,

I've been planning a project of building a room in the garden within permitted developments for nearly 2 years and I still can't get my head around foundations/footings and other ground work.

Do I start with digging the foundations, or level the ground first with a wacker plate and then dig? Because the top surface is soft and crumbling.

And then regarding the floor of the room, when do I dig it to put the floor insulation and concrete it? Before building the walls or after?

What is the order of the materials of the floor, 1. hardcore, 2. insulation, 3. Concrete? Anything else.

Any help will be highly appreciated!

Thank you.

 

[jasonzyx]

Hi,

I've been planning a project of building a room in the garden within permitted developments for nearly 2 years and I still can't get my head around foundations/footings and other ground work.

Do I start with digging the foundations, or level the ground first with a wacker plate and then dig? Because the top surface is soft and crumbling.

And then regarding the floor of the room, when do I dig it to put the floor insulation and concrete it? Before building the walls or after?

What is the order of the materials of the floor, 1. hardcore, 2. insulation, 3. Concrete? Anything else.

Any help will be highly appreciated!

Thank you.

It would be sensible and economical to dig all required digging while the machinery is on site.
No point whacking it then digging it up again.
Foundations and footings are more or less interchangeable, but I suppose it could be argued that foundation is concrete strip or appropriate alternative, but footings is the initial brickwork.

Other groundworks can include drainage, landscaping etc.

Floor slab: cleared of all vegetation, hardcore (whacked to refusal), sand blinding, DPM, insulation, thin DPM, concrete, screed.
It is possible to lay insulation under the DPM, but you may need different insulation, and the second thin DPM can be omitted.
The screed may or may not be required, depending on intended use.

 

[Noah1234]

Thank you so much for your reply! You have no idea how much better I feel now!

Its very hard to get proper information in such a project. Some builders seem to just build, they either don't know or they give advice for which ever is easier for them!

Do I fill concrete up to floor level or lower and start building the wall below ground level?

 

[jasonzyx]

If it's subject to Building Control you need to inform yourself of the requirements.
Size matters, (as does intended use) more than 30 meters² and Building Control is involved. You must comply with their requirements.
Without knowing more about your specific circumstances it is not possible to advise.

In general, and this might not apply in your case, concrete strip foundation and suitable block or brick to just below ground level, or trench fill (concrete up to just below ground level).

Don't interchange the terms floor level and ground level. They are different.
Ground level is considered that outside, and floor level (finished floor level - ffl) is that considered inside.

 

[noseall]

You build in layers i.e. starting with the lowest. Foundations, drains, block/brick-work, oversite etc.

We dig the foundations and pull the oversite material off at the same time. We also remove perimeter material during this process so that we can stone-up the site perimeter so that we are not working in mud.

The questions you are asking are fundamental and lead me to believe that you may be better off getting someone in.

 

[Notch7]

Thank you so much for your reply! You have no idea how much better I feel now!

Its very hard to get proper information in such a project. Some builders seem to just build, they either don't know or they give advice for which ever is easier for them!

Do I fill concrete up to floor level or lower and start building the wall below ground level?

you have 2 separate things:

A foundation, which these days is usually a trench either 450mm or 600mm wide x min of 1000mm deep as measured from finished ground level. You finish the top of the foundation to suit a number of blocks or bricks to build up to your dpc level (generally that is the underside of a door cill. Depth of foundation is determined by soil type and influence of trees or hedges.

if you have ground bearing soil, then you can dig down and lay a concrete slab floor. You will need to dig down below top soil, ie to hard sub soil. The depth you dig will depend on your floor construction: For example: hardcore, sand blinding, damp proof membrane, concrete, insulation, screed, floor finish. Typically that lot adds up to around 450mm.

 

[Noah1234]

Thank you all for your help. I have a better picture. I just needed that rough idea so I don't get messed about but non experienced/non honest builders.

The room will be 30 sqm so no building reg required.

It will be also 2.5m high flat roof. That bit is also a unclear to me as the garden is a little uneven, upto 0.5m variation.
Where do I measure the 2.5 m height from?

 

[noseall]

The room will be 30 sqm so no building reg required

It needs to be constructed largely of non-combustible materials and be at least 1m from the boundary also. Be careful with the flat roof regards 'non-combustible'.