On Sat, 28 Feb 2004 17:30:09 -0000, "Julian"
wrote:

Hi all

At the back of our garden I am planning to build a concrete pad as a base
for a garden shed.

The ground rises a bit towards the back of the garden and we have had to
excavate in order to level the ground.

Consequesntly the concrete pad will need a wall on 3 sides to support the
earth behind it if you see what I mean.


I had the opposite situation - i.e. the ground slopes a little
downwards going away from the house. Rather than digging down at
the house end, I elected to have the base one course of bricks above
surrounding ground at the house end and four at the far end. Not
wishing to see the ugly sides of the concrete, which could have been
done by shuttering it with wood and pouring, I have bricks matching
the house ones around the edge. It's the opposite to what you are
doing, but the principle is the same.

The construction was done by levelling the area, and then digging out
a trench about 250mm wide and about 300mm deep around the edge and
filling with concrete.

This was allowed to cure for a couple of days and the wall was then
built on top.

Two days later some hardcore was put into the base area and finally
concrete poured and levelled.

The area is about 3mx3.5m and expansion joints weren't used. I'm not
certain about the point at which that is required, but it wasn't for
this size, which is larger than you are talking about. THere
haven't been any problems with it.



The pad itselef will be about 8'by 6' which includes about a foot extra
width for the small wall on the 3 sides (shed is 7' x 5'). The wall willl
only be 4 bricks high.

To support the shed, I have read that no hardcore foundation is necessary
and the concrete should be about 3 inches thick. However I would think that
the wall will need a bit more support.

The base depth should be OK, but the wall should have some foundation
to support it.


My qurestions are these; How should I approach this? Should I dig down a bit
further 1 foot from the edge on the 3 sides and put extra concrete in there
or will I be able to get away with 3 inches all over.

I would dig a bit further down. I would also arrange for the top of
the base to be a bit above the ground at the front of the garden
rather than strictly at ground level, even if only by 30mm or so.
You may find that some water finds its way from the higher ground at
the bottom onto the concrete. Having the plinth a shade above the
surrounding lower ground will allow water to drain off. You don't
really want the bearers of the shed sitting in water. To this end,
make sure that the base is either dead level or has a very fractional
slope towards the low end. You can level the shed itself if
necessary by using strips of wood on top of the bearers.

Some other things to consider:

- It's probably worth renting a concrete mixer for the base concrete.
Even for this relatively small area, it's a lot of concrete and if you
can mix and pour it all relatively quickly, the result will be better

- When you put down the timber bearers for the shed, it's worth
putting strips of DPC material under them on the concrete (will stop
dampness that soaks through the concrete from reaching the wood), and
above them to completely isolate the shed base.

- It may be worth having the base slightly larger where the wall is so
that there is a gap of say 100-150mm between it and the shed walls.
This will allow getting a roller on a stick down there so that you can
treat the walls with preservative in later years.



Will I need any
expansion joints in the pad as well. If I should put some in where should I
put them.

This is my first attempt at doing this sort of thing and am quite looking
forward to the challenge.

TIA

Julian


..andy

To email, substitute .nospam with .gl