Hi All

Have dug out and shuttered for 2 100mm thick shed bases

area 10' x 10' and 10' x 6'

Paving expert site recommends a 6 to 1 mix for bases generally but this is
not a big one

6 of ballast sand mix 1 of ordinary portland

I wonder if a weaker mix say 9 to 1 would be adequate as a 30% reduction in
the cement cost would be handy

Due to access and having to do it on a sunday this will all be mixed on site

Regards

On 10 July, 08:11, "TMC" wrote:
Hi All

Have dug out and shuttered for 2 100mm thick shed bases

area 10' x 10' and 10' x 6'

Paving expert site recommends a 6 to 1 mix for bases generally but this is
not a big one

6 of ballast sand mix 1 of ordinary portland

I wonder if a weaker mix say 9 to 1 would be adequate as a 30% reduction in
the cement cost would be handy

Due to access and having to do it on a sunday this will all be mixed on site

Regards

Would not recommend weakening it as it will become v porous. Ship and
happorth tar?
chris

TMC wrote:

Hi All

Have dug out and shuttered for 2 100mm thick shed bases

area 10' x 10' and 10' x 6'

Paving expert site recommends a 6 to 1 mix for bases generally but this is
not a big one

6 of ballast sand mix 1 of ordinary portland

I wonder if a weaker mix say 9 to 1 would be adequate as a 30% reduction
in the cement cost would be handy

Due to access and having to do it on a sunday this will all be mixed on
site

Regards

With paving slabs on top or not?

If the sand mix is just as a bed for the slabs, 9:1 will be fine to stop it
migrating.

If you are putting a shed on the sand, stick with the 6:1...

--
Tim Watts

On 10/07/2011 08:11, TMC wrote:

Have dug out and shuttered for 2 100mm thick shed bases

area 10' x 10' and 10' x 6'

snip

I wonder if a weaker mix say 9 to 1 would be adequate as a 30% reduction
in the cement cost would be handy


If the sub-base is well compacted hardcore or stone, and if the eventual
appearance of an odd small crack isn't too critical. I'd drop the
thickness to 3", but stick with 1:6. For simple wooden sheds used for
ordinary domestic purposes, you'd get away with even less thickness than
that.

It's easy to over-engineer these things, especially when it's someone
else's money.

Don't mix it too wet (strength is a function of water/cement ratio), and
compact it well to get rid of air bubbles, then cover it to prevent
over-rapid drying out. A layer of polythene under the concrete keeps it
wet while it's curing and dry once it's a shed floor, but it does need
the sub-base to be blinded with sand, and care while laying the
concrete, to avoid puncturing it.


--
Kevin Poole

"Kevin Poole" wrote in message
...
On 10/07/2011 08:11, TMC wrote:

Have dug out and shuttered for 2 100mm thick shed bases

area 10' x 10' and 10' x 6'

snip

I wonder if a weaker mix say 9 to 1 would be adequate as a 30% reduction
in the cement cost would be handy


If the sub-base is well compacted hardcore or stone, and if the eventual
appearance of an odd small crack isn't too critical. I'd drop the
thickness to 3", but stick with 1:6. For simple wooden sheds used for
ordinary domestic purposes, you'd get away with even less thickness than
that.

thanks for the reples

6:1 it will be and sticking with 100mm

Regards

TMC wrote:
Hi All

Have dug out and shuttered for 2 100mm thick shed bases

area 10' x 10' and 10' x 6'

Paving expert site recommends a 6 to 1 mix for bases generally but
this is not a big one

6 of ballast sand mix 1 of ordinary portland

I wonder if a weaker mix say 9 to 1 would be adequate as a 30%
reduction in the cement cost would be handy

Due to access and having to do it on a sunday this will all be mixed
on site
Regards

You do know that that's about 1.5m3 of concrete you have to mix?
If it were mine, I'd have dug the top inch of grass and soil, then shuttered
3 inches deep, so that the surface was 2 inches above surrounding ground,
I'd have saved half a cube of concrete and the end result wouldn't be as at
risk of flooding etc.
Saying that, the last one I built, a few months ago (for a large wooden
wendy house, but the principal is still the same) I just scraped out three
channels about 6 inches deep and mixed a fairly strong, dry concrete, this
went about 3 inches deep and I laid three rows of bricks on the strips.
I then laid paving slabs onto these minature walls, leaving inch gaps
between the slabs, underneath being hollow.
The end rusult was a free draining solid base, which cost about 20 quid and
took 4 hours, given that we used 2nd hand slabs and old bricks.

the only visible parts of it are the dwarf wall and the outer edge of the
slabs.