FOOTINGS 1.8m

[Shytalkz]

...she used a table of tree types, distance from the building etc, etc. She told me that I either dig down 1.8m if I left the conifers in or 1m if I removed them.

She's referring to the NHBC table that I mentioned, which is the accepted guidance. If she's saying 1m, then either the tree's not very big/mature, or it is and she's forgotten to take heave into account.

If you leave it in, you don't need any board on the outside of the footing, as the soil won't have the potential to heave. If you intend planting around the perimeter of the house, NHBC chap 4.2 suggests 1.25m min depth.

 

[Bowness72]

as some of her other comments have left me scratching my head I now doubt or question anything she says......

What are her other comments ? as you originally thought the foundation depth was odd also

 

[GaryinAshby]

Advising me to have a soak away with conifers round it to help the soakaway to work as the soil is hard clay, insisting that there is a minimum of 665mm return on walls (ie. no window can be less than 665mm to the corner of a building). Plus a few other bits & pieces, but seeing as this is a one-off extension & I'm no expert it isn't worth trying to argue.......

 

[^woody^]

The bit about the window is not quite correct. A window can be close to a corner, but if less than 675mm, then you may have to provide a calculation to prove that it is structurally sound.

It's a bit of a nonsense, as if you look at all the houses built in the past, just look where the windows and doors are - and let me know if they are still standing or are a heap of rubble.

I think all the LA's got some sort of guidance note a few years ago, as they have only been enforcing this nonsense relatively recently.

I can understand the thinking behind the soak-away, but if the ground is already saturated, and the tree not drinking much (ie winter) then the idea fails miserably

 

[Shytalkz]

As an experiment some years ago, the company for whom I worked at the time were given two Airey Houses on a clay site to play with and come up with a new approach to refurbing them, part of which involved us seeing if we could keep the moisture content reasonably stable to offset the moisture drawing from nearby trees, which was causing them to move.

So, we watered one around its perimeter and not the other. There was no science to it: we just watered it when it looked dry and the volume of water was neither measure nor calculated. Comparison of the two halves after a year or so showed that the one we watered had barely moved, but the other one had gone for a wander.

Others have tried to come up with a foolproof system that delivers the corect quantity of water as and when required, but, given the slow uptake of moisture in clays, as far as I am aware, no one has had any success and it's difficult to see how they would.

But the principle is good on a wholly unscientific basis of approach if you're suffering from a bout of movement on clay soils and want to try and keep it in check.

 

[Shytalkz]

I think all the LA's got some sort of guidance note a few years ago, as they have only been enforcing this nonsense relatively recently.

665mm used to be the old "deemed to satisfy" dimension in BRegs before it all got split up into bits. I can usually get a lesser dim to work, although if there's next to no return, then a windpost can solve matters. But, that's the calculation approach and, as you say, there are plenty with tiddly dims that stand there quite happily. Prescriptive intransigence again...

I can understand the thinking behind the soak-away, but if the ground is already saturated, and the tree not drinking much (ie winter) then the idea fails miserably

If it's an evergreen? however, I think it's a pants idea myself.

 

[GaryinAshby]

Thanks. The first thing that sprang to mind was a garage. The up & over door sometimes has a 9" brick either side (admittedly 9" thick).

 

[Bowness72]

A garage is not classified as a habitable building so you cant really compare it to that, but as previously mentioned by others on here it can be done but just needs to be proved as adequate taking into account all relevant building and site specific data.