Regs for ground floor wooden suspended floor (no slab)

[matt5791]

I am going to be building an extension to the rear of our property - because of the way the ground slopes, gently, front to rear of the property, the ground floor level is quite high at the rear (3-4ft)

I want to avoid having to "make up" a lot of ground in the extension in order to bring the level up. Therefore I want to construct a timber floor (like the other ground floors in the house - it's Victorian) with vented bricks below the floor line.

Question is - are there any building regs relating to insulation and other elements of this design (aside from the correct spec of joist etc which is obvious) Or can construction be largely the same as the Victorians did it?

Many thanks for any help.

 

[tony1851]

Just put some decent insulation between the joists (eg 4" Kingspan); make sure you have sufficient air bricks; cover the exposed earth bellow with approx 2" compacted stone on polythene sheet.

 

[^woody^]

The stuff you dig out of the foundations, can be the fill for a solid floor

 

[RonnyRaygun]

Just put some decent insulation between the joists (eg 4" Kingspan); make sure you have sufficient air bricks; cover the exposed earth bellow with approx 2" compacted stone on polythene sheet.

Just make sure you check your perimeter / area ratio to get the correct thickness.
http://www.north-herts.gov.uk/11_-_u-values_of_elements.pdf

The stuff you dig out of the foundations, can be the fill for a solid floor

You not worried about settlement Woody?

 

[^woody^]

You not worried about settlement Woody?

I would not be, and the OP should not be either is it's all whacked down and done properly

 

[tony1851]

I would not be, and the OP should not be either is it's all whacked down and done properly

The OP said the difference in level was 3-4ft.
Would wacking it down not put lateral pressure on the wall?
I would never do a solid floor with that difference in level.

 

[RonnyRaygun]

You not worried about settlement Woody?

I would not be, and the OP should not be either is it's all whacked down and done properly

I reckon you'd have to do it in layers of 2 or 3 inches to get sufficient compaction.
Might save on the cost of filling a skip but looks like a lot of work to me.

And agree with Tony re. lateral pressure.

 

[^woody^]

The OP says "ground slopes gently" so what does that mean?

Then, 3-4ft which is a bit of a difference, so again which is is it?

At least 350mm will be coming off anyway for the vegetation layer and new floor depth, so that does not actually leave a great deal of infill in terms of depth or area

 

[maltaron]

It is reasonable to assume that the existing ground is probably around 500mm below floor level at the existing building wall. If we assume a 3 m extension I would think to surplus from the foundations will create about a third of the fill needed. Also, yes, the BCO will need to approve your joist sizes and insulation.

 

[Deluks]

Both, if there's space.
Suspended timber and put all the fill under, purely to avoid the cost of a skip and time spend loading it. As mentioned, blind it with weak mix or poly/stone.

 

[maltaron]

Just another point which may be useful. I have just done a similar extention on sloping ground(floor was just under 3ft at worst point). I put a damp proof membrane and average 2" shovel finish concrete down and left a doorway through the wall under the floor. This makes a useful storage space. (or dig out another 3ft and make a cellar)