I'm about to make a concrete base for a 4.5m x 3.0m workshop. The timber
shed will be supplied in panels by the local sawmill, who know how to
design them for the severe wind and rain we often have around here.

Their recommendation is to form the base with an upstand as shown below,
so that the wooden frame sits on top but the boards can overhang to
prevent water driving in underneath.

(view only in a fixed pitch font)
_______ ______
___| |___
| |

To complete the picture, the base will be in a corner between two
dry-stone walls. One side and one end of the foundation will be poured
right up to the bases of the walls, so vertical shuttering at the lower
level will only be needed for the remaining side and end. Also there is
about a 0.3m fall in the ground from end to end. The soil cover is very
thin, so that will be removed to expose the very firm rocky subsoil. The
fall will then be mostly levelled up with solidly rammed hardcore, but
with an adequate cover of concrete all over.

The other obvious requirement is that what's drawn as a horizontal
level of concrete should actually slope away slightly all round, to
provide a runoff.

My question is: how to shutter and pour the concrete?

There seem to be altogether too many alternatives... shutter it to cast
the entire shape in a single pour, or various options for two pours
and/or adding the sloping skirt later. I'd very much welcome comments
and suggestions to narrow down the range.



--
Ian White

On Wed, 5 Oct 2005 13:17:04 +0100, Ian White
wrote:


I'm about to make a concrete base for a 4.5m x 3.0m workshop. The timber
shed will be supplied in panels by the local sawmill, who know how to
design them for the severe wind and rain we often have around here.

Their recommendation is to form the base with an upstand as shown below,
so that the wooden frame sits on top but the boards can overhang to
prevent water driving in underneath.

(view only in a fixed pitch font)
_______ ______
___| |___
| |

To complete the picture, the base will be in a corner between two
dry-stone walls. One side and one end of the foundation will be poured
right up to the bases of the walls, so vertical shuttering at the lower
level will only be needed for the remaining side and end. Also there is
about a 0.3m fall in the ground from end to end. The soil cover is very
thin, so that will be removed to expose the very firm rocky subsoil. The
fall will then be mostly levelled up with solidly rammed hardcore, but
with an adequate cover of concrete all over.

The other obvious requirement is that what's drawn as a horizontal
level of concrete should actually slope away slightly all round, to
provide a runoff.

My question is: how to shutter and pour the concrete?

There seem to be altogether too many alternatives... shutter it to cast
the entire shape in a single pour, or various options for two pours
and/or adding the sloping skirt later. I'd very much welcome comments
and suggestions to narrow down the range.

What I would do
1) Shutter it (but not the upstand), and put the slight slope into it
in one pour, unless the mix if very runny this won't be a problem to
get the slope into it.
2) Add the upstand with a row of 7N dence concrete blocks, or concrete
bricks round the edge
3) put down a DPM, and insulation for a quality job, of an insuated
floor.



Rick

In article , says...

I'm about to make a concrete base for a 4.5m x 3.0m workshop. The timber
shed will be supplied in panels by the local sawmill, who know how to
design them for the severe wind and rain we often have around here.

Their recommendation is to form the base with an upstand as shown below,
so that the wooden frame sits on top but the boards can overhang to
prevent water driving in underneath.

(view only in a fixed pitch font)
_______ ______
___| |___
| |

To complete the picture, the base will be in a corner between two
dry-stone walls. One side and one end of the foundation will be poured
right up to the bases of the walls, so vertical shuttering at the lower
level will only be needed for the remaining side and end. Also there is
about a 0.3m fall in the ground from end to end. The soil cover is very
thin, so that will be removed to expose the very firm rocky subsoil. The
fall will then be mostly levelled up with solidly rammed hardcore, but
with an adequate cover of concrete all over.

The other obvious requirement is that what's drawn as a horizontal
level of concrete should actually slope away slightly all round, to
provide a runoff.

My question is: how to shutter and pour the concrete?

There seem to be altogether too many alternatives... shutter it to cast
the entire shape in a single pour, or various options for two pours
and/or adding the sloping skirt later. I'd very much welcome comments
and suggestions to narrow down the range.

By far the easiest in terms of shuttering will be to pour a flat slab,
then add the raised bit, and finally slap on a bit of mortar to provide
the runoff.

In article ,
Rob Morley wrote:
In article , says...

I'm about to make a concrete base for a 4.5m x 3.0m workshop. The timber
shed will be supplied in panels by the local sawmill, who know how to
design them for the severe wind and rain we often have around here.

Their recommendation is to form the base with an upstand as shown below,
so that the wooden frame sits on top but the boards can overhang to
prevent water driving in underneath.

(view only in a fixed pitch font)
_______ ______
___| |___
| |

To complete the picture, the base will be in a corner between two
dry-stone walls. One side and one end of the foundation will be poured
right up to the bases of the walls, so vertical shuttering at the lower
level will only be needed for the remaining side and end. Also there is
about a 0.3m fall in the ground from end to end. The soil cover is very
thin, so that will be removed to expose the very firm rocky subsoil. The
fall will then be mostly levelled up with solidly rammed hardcore, but
with an adequate cover of concrete all over.

The other obvious requirement is that what's drawn as a horizontal
level of concrete should actually slope away slightly all round, to
provide a runoff.

My question is: how to shutter and pour the concrete?

There seem to be altogether too many alternatives... shutter it to cast
the entire shape in a single pour, or various options for two pours
and/or adding the sloping skirt later. I'd very much welcome comments
and suggestions to narrow down the range.

By far the easiest in terms of shuttering will be to pour a flat slab,
then add the raised bit, and finally slap on a bit of mortar to provide
the runoff.

Why not pour the central raised bit (flat) then the outer rim at a lower,
sloping, level?

--
John Cartmell john@ followed by finnybank.com 0845 006 8822
Qercus magazine FAX +44 (0)8700-519-527 www.finnybank.com
Qercus - the best guide to RISC OS computing

In article ,
says...
In article ,
Rob Morley wrote:
snip
By far the easiest in terms of shuttering will be to pour a flat slab,
then add the raised bit, and finally slap on a bit of mortar to provide
the runoff.

Why not pour the central raised bit (flat) then the outer rim at a lower,
sloping, level?

If you pour the central bit first you need to shutter the full depth on
four sides, then two sides for the second pour. Doing it the way I
suggested only needs shuttering on two sides for the main pour, then
minimal shuttering for the top slab.