outbuilding foundation requirements

[teracir]

HI,

I am looking to build an outbuilding for storage and need some assistance regarding the foundation. I have reviewed alot of threads on this forum and others regarding foundation and have a basic understanding of what is required.

I am looking to build a 7m by 5m single storey outbuilding. the new building is about 6m away from the house and is 1m away from any of the boundary. since it is greater than 30m2 I am assuming i need to report the matter for palnning permission?

I am under the assumption that i need to dig a trench 450mm wide and 600mm deep, fill with concrete to about 150mm below ground, lay dpm and fill another 150mm on top (use mesh if possible), is this correct.

I intend to use breeze blocks and start building from the ground level. the wall will be double and there will be no gaps between the blocks since it is storage space purley.

please provide advice if this is correct or if you see a better way of doing this?

 

[noseall]

sounds like you have it sussed to me.

the concrete foundation needs to project 150mm beyond the inner and outer leaves of the wall, so make the foundation trench 300mm wider than wall thickness.

dig down to good virgin soil. depth will depend upon ground conditions, ground levels, proximity to large shrubs or trees and possibly water table.

i would use dense 7n concrete blocks for the outer skin.

 

[teracir]

thanks for the reply,

since I am proposing to use breeze blocks, what are the advantages of starting courses (possibly 2) below ground level?

i was intending to use the aerated breeze blocks similar to those on wickes website, would they be efficient in external environments since they are primarily designed for internal wall?

my next door neigbour has a tree ground at the garden fence (garden wall will be 1m away from the fence), how will this impact the depth i dig to and the concrete foundation?

thanks again for any help and tips...

 

[noseall]

any masonry below damp should be of a quality no less than 40nuton f.l. bricks laid in strong 3;1 mortar or 7nuton solid concrete blocks.

i personally would not use airated blocks externally. as said previous i would use concrete blocks, both for looks and durability. if you were thinking of rendering then hemelites (lightweight aggregate) would be ok.

i think if a mature tree or large shrubs even, are within 4m* of the building then a deeper foundation may be necessary. also if you are digging in clay then precautions against 'clay heave' may be necessary.

*the closer the tree, the deeper the dig.