On Sun, 27 Apr 2014 14:28:03 +0100, John Rumm
wrote:

So far so good....

and top off with sand.
Don't use any cement, there's no point, it's just a bodge method.

Could I suggest you go read some of the British standards on paving
techniques? To describe using a bound bedding layer (i.e. one containing
cement or lime) as a "bodge" is inaccurate and misleading.

Generally, "sand only" screeds tend to be used for smaller element
paving such as blocks and sets, and screeds with a binder used for
larger slabs - however this is not a hard and fast rule.

However the critical requirement of any sand only screed is that the
edge is adequately retained - typically with a mortared in place bedded
on course of blocks or edging stones, but sometimes just a concrete
haunch. Without the edge restraint, the sand will migrate out, and will
also get migrated by insects. and worms etc.

So greenhouse bases put solely on a slab sand base - especially in a
very wet area - will be fairly wobbly after about how long?

What about postcreting posts in for the corners for my greenhouse
base, someone's suggested pressure treated boards around the bottom to
make like a raised bed to sit it on.







For chapter and verse on bedding courses, have a look at:

http://www.pavingexpert.com/layflag3.htm#bornb

For general on flags:

http://www.pavingexpert.com/layflag1.htm
--
http://www.voucherfreebies.co.uk

On 30/04/2014 10:54, mogga wrote:
On Sun, 27 Apr 2014 14:28:03 +0100, John Rumm
wrote:

So far so good....

and top off with sand.
Don't use any cement, there's no point, it's just a bodge method.

Could I suggest you go read some of the British standards on paving
techniques? To describe using a bound bedding layer (i.e. one containing
cement or lime) as a "bodge" is inaccurate and misleading.

Generally, "sand only" screeds tend to be used for smaller element
paving such as blocks and sets, and screeds with a binder used for
larger slabs - however this is not a hard and fast rule.

However the critical requirement of any sand only screed is that the
edge is adequately retained - typically with a mortared in place bedded
on course of blocks or edging stones, but sometimes just a concrete
haunch. Without the edge restraint, the sand will migrate out, and will
also get migrated by insects. and worms etc.

So greenhouse bases put solely on a slab sand base - especially in a
very wet area - will be fairly wobbly after about how long?

What about postcreting posts in for the corners for my greenhouse
base, someone's suggested pressure treated boards around the bottom to
make like a raised bed to sit it on.







For chapter and verse on bedding courses, have a look at:

http://www.pavingexpert.com/layflag3.htm#bornb

For general on flags:

http://www.pavingexpert.com/layflag1.htm

For Gods sake read the OP.

"I have some "stepping stones" set in to my lawn: 9x18 cms and also a
couple of paving slabs : 60x75 cms which have sunk."

He's not laying a patio or even a path.

On 30/04/2014 10:54, mogga wrote:
On Sun, 27 Apr 2014 14:28:03 +0100, John Rumm
wrote:

So far so good....

and top off with sand.
Don't use any cement, there's no point, it's just a bodge method.

Could I suggest you go read some of the British standards on paving
techniques? To describe using a bound bedding layer (i.e. one containing
cement or lime) as a "bodge" is inaccurate and misleading.

Generally, "sand only" screeds tend to be used for smaller element
paving such as blocks and sets, and screeds with a binder used for
larger slabs - however this is not a hard and fast rule.

However the critical requirement of any sand only screed is that the
edge is adequately retained - typically with a mortared in place bedded
on course of blocks or edging stones, but sometimes just a concrete
haunch. Without the edge restraint, the sand will migrate out, and will
also get migrated by insects. and worms etc.

So greenhouse bases put solely on a slab sand base - especially in a
very wet area - will be fairly wobbly after about how long?

They may never get wobbly - although the levels will usually shift.
Often there will be no trace of the sand if you lift a slab later.

Frequently wet areas are worse - but the effect will vary with soil
conditions.

If the slabs are above ground level (rather than on it "in" it) then the
edge ones usually tip outward as the sand escapes from the edge.

What about postcreting posts in for the corners for my greenhouse
base, someone's suggested pressure treated boards around the bottom to
make like a raised bed to sit it on.

What kind of soil do you have?

For slabs used as a shed or greenhouse base, adding enough cement to the
sand to let it set a little once laid is usually all that's needed to
keep it in place. (used as a dry mix - no need to actually turn it into
mortar prior to laying)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 30/04/2014 13:14, David Hill wrote:
On 30/04/2014 10:54, mogga wrote:
On Sun, 27 Apr 2014 14:28:03 +0100, John Rumm
wrote:

So far so good....

and top off with sand.
Don't use any cement, there's no point, it's just a bodge method.

Could I suggest you go read some of the British standards on paving
techniques? To describe using a bound bedding layer (i.e. one containing
cement or lime) as a "bodge" is inaccurate and misleading.

Generally, "sand only" screeds tend to be used for smaller element
paving such as blocks and sets, and screeds with a binder used for
larger slabs - however this is not a hard and fast rule.

However the critical requirement of any sand only screed is that the
edge is adequately retained - typically with a mortared in place bedded
on course of blocks or edging stones, but sometimes just a concrete
haunch. Without the edge restraint, the sand will migrate out, and will
also get migrated by insects. and worms etc.

So greenhouse bases put solely on a slab sand base - especially in a
very wet area - will be fairly wobbly after about how long?

What about postcreting posts in for the corners for my greenhouse
base, someone's suggested pressure treated boards around the bottom to
make like a raised bed to sit it on.







For chapter and verse on bedding courses, have a look at:

http://www.pavingexpert.com/layflag3.htm#bornb

For general on flags:

http://www.pavingexpert.com/layflag1.htm

For Gods sake read the OP.

Did you spot the "which have sunk" bit?

Assuming that was the problem he wanted to fix...

(note also the discussion has moved onto greenhouse bases)

"I have some "stepping stones" set in to my lawn: 9x18 cms and also a
couple of paving slabs : 60x75 cms which have sunk."

He's not laying a patio or even a path.

So?

If you want to be able to level them and not have them sink again, do
what has been suggested...

Lift the stone. Unless the soil is rock hard and stays that way all
year, chuck in a thin layer of type 1 and ram it down so you have a good
sub base to work from. Now rather than re-bedding the stone on just
sharp sand, add a small amount of cement to it. Its only going to take 5
minutes to do it properly. That will stop the worms etc from romping off
into the lawn with your bedding, or having it flushed out with too much
water.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Wed, 30 Apr 2014 15:10:22 +0100, John Rumm
wrote:


So greenhouse bases put solely on a slab sand base - especially in a
very wet area - will be fairly wobbly after about how long?

They may never get wobbly - although the levels will usually shift.
Often there will be no trace of the sand if you lift a slab later.

Frequently wet areas are worse - but the effect will vary with soil
conditions.

The plot I am thinking of has slabs covered with water when it rains
a lot.

https://www.flickr.com/photos/25345470@N02/13694025513/

https://www.flickr.com/photos/253454...n/photostream/
The greenhouse at the end ..
It is the second wettest plot. Up from the wettest one which is
diagonally left in the second picture.


If the slabs are above ground level (rather than on it "in" it) then the
edge ones usually tip outward as the sand escapes from the edge.

What about postcreting posts in for the corners for my greenhouse
base, someone's suggested pressure treated boards around the bottom to
make like a raised bed to sit it on.

What kind of soil do you have?


Soily with masses of clay underneath the wet plot. He tried digging
through it but gave up.

Mine is much more loamy on the bit I want to put my greenhouse on and
it's a bed I've dug and cultivated so it's a bit soft. Lovely for
growing in though.
Would I be better finding a different bit for the greenhouse? The
whole plot gets the sun and there's no issue of shading another plot
on most of it.

For slabs used as a shed or greenhouse base, adding enough cement to the
sand to let it set a little once laid is usually all that's needed to
keep it in place. (used as a dry mix - no need to actually turn it into
mortar prior to laying)

'k. Ta. I think they have just used sand from the bag - not seen
cement bags anywhere.
--
http://www.voucherfreebies.co.uk

On 30/04/14 15:10, John Rumm wrote:
For slabs used as a shed or greenhouse base, adding enough cement to the
sand to let it set a little once laid is usually all that's needed to
keep it in place. (used as a dry mix - no need to actually turn it into
mortar prior to laying)

About 30 years ago my dad and I put a new shed in the "woods" at the end
of our garden. Ground was rough as shite and not stable.

We levelled with a rake, dad made a boundary frame with some 3x1 (ish)
pegged at each corner.

We filled it with dry 6:1 sand:cement. Rammed down by hand, levelled and
slabs laid.

Gave it a good couple of hosings from the top then installed the shed.

Despite the frame being proud of the ground on 2 sides and the wooden
frame eventually rotting and falling off the slabs stayed put.

6:1 is weak but it's enough to hold the general shape.