Pre-compacted hardcore thickness
 

I've been googling for this but I seem to have lost my mojo.

I'm going to be laying a patio soon and plan to use a 75mm layer of
compacted dtp1 on top of soil. Then bedding layer and then flags.

The thing I can't seem to find is any indication of how thick the
uncompacted layer of dtp1 should be so that after the appropariate
number of passes with a whacker plate it compacts down to ~75mm. Shoudl
it be 80mm, 85 mm, 150mm or what? I'm not after millimeter perfect I
just have no idea how much this stuff will compact.

I've ben using the excellent pavingexpert site and I have a horrible
feeling it will say somewhere on there, but I havn't found it yet.

thanks in advance

--
Steve F

Pre-compacted hardcore thickness
 

Fitz wrote:
I've been googling for this but I seem to have lost my mojo.

I'm going to be laying a patio soon and plan to use a 75mm layer of
compacted dtp1 on top of soil. Then bedding layer and then flags.

The thing I can't seem to find is any indication of how thick the
uncompacted layer of dtp1 should be so that after the appropariate
number of passes with a whacker plate it compacts down to ~75mm.
Shoudl it be 80mm, 85 mm, 150mm or what? I'm not after millimeter
perfect I just have no idea how much this stuff will compact.

I've ben using the excellent pavingexpert site and I have a horrible
feeling it will say somewhere on there, but I havn't found it yet.

thanks in advance

It doesn't go down very far so don't go berserk with it!
If you want to put down 75mm and then whack it this is perfectly adequate,
although for a patio it's probably not required at all considering it's only
taking foot traffic....I use 100mm compacted for drives, with a 50mm bed of
grit and then block pavers or flags and I've never had one sink yet, even
those who have 2 or 3 large Mercs, although I don't use a whacker for this,
I use a vibrating roller - that *does* take it down! - it pulverises it into
the subsoil and if it's wet you can get a finish on it that you could mix
sand & cement on with a shovel and not get any stones in it.

For a patio I would use only an inch or two, just as a firm base for your
sand/cement mix, to get 50mm all over (prior to whacking) use
trammels....two lengths of 50mm timber down each side, fill in with
hardcore, then run a trammel (another length of straight timber) across the
top of both (like a letter H)so that the thickness is even and the surface
is fairly flat, then whack the lot a few times, you'll notice dips and
lumps, fill in the dips with finer grade stuff or grit sand and scrape off
the lumps and whack again, you don't need to get it like a snooker table,
but the flatter you do get it, the easier the flag laying is....use a
stringline for your flags and lay them on 5 big blobs of grit sand and
cement (no plasticiser or any other additives), for getting the blobs equal,
I normally use a 3 inch plant pot and they come out like little uniform
sandcastles!....a couple of *taps* with the flagging mallet and they are
done, don't walk on flags for 12 hours after laying.


HTH

Pre-compacted hardcore thickness
 

Phil L wrote:
Fitz wrote:
I've been googling for this but I seem to have lost my mojo.

I'm going to be laying a patio soon and plan to use a 75mm layer of
compacted dtp1 on top of soil. Then bedding layer and then flags.

The thing I can't seem to find is any indication of how thick the
uncompacted layer of dtp1 should be

It doesn't go down very far so don't go berserk with it!

For a patio I would use only an inch or two, just as a firm base for your
sand/cement mix, to get 50mm all over (prior to whacking) use
trammels....two lengths of 50mm timber down each side, fill in with
hardcore, then run a trammel (another length of straight timber) across the
top of both (like a letter H)so that the thickness is even and the surface
is fairly flat,

HTH

Thanks for the info - exactly what I was after. I'll probably aim for
about 75mm uncompacted then see where it ends up.

Presumably if this stuff sets up as hard as described after compaction,
once you take the trammels away you don't have to worry about the edges
falling away? I've been wondering if I should use an edge stone to
provide a boundary around the edge of the sub-base.

--
Steve F

Pre-compacted hardcore thickness
 

Fitz wrote:
Phil L wrote:
Fitz wrote:
I've been googling for this but I seem to have lost my mojo.

I'm going to be laying a patio soon and plan to use a 75mm layer of
compacted dtp1 on top of soil. Then bedding layer and then flags.

The thing I can't seem to find is any indication of how thick the
uncompacted layer of dtp1 should be

It doesn't go down very far so don't go berserk with it!

For a patio I would use only an inch or two, just as a firm base for
your sand/cement mix, to get 50mm all over (prior to whacking) use
trammels....two lengths of 50mm timber down each side, fill in with
hardcore, then run a trammel (another length of straight timber)
across the top of both (like a letter H)so that the thickness is
even and the surface is fairly flat,

HTH

Thanks for the info - exactly what I was after. I'll probably aim for
about 75mm uncompacted then see where it ends up.

Presumably if this stuff sets up as hard as described after
compaction, once you take the trammels away you don't have to worry
about the edges falling away? I've been wondering if I should use an
edge stone to provide a boundary around the edge of the sub-base.

The edges will need support yes, either kerbs or filled in with concrete
later, they will cave in after the trammels are taken away, but the idea is
to s-l-i-d-e the trammel out and infill it using a trowel, so that it's all
level(ish) prior to whacking it.
The hardcore won't be as hard as I mentioned above using just a whacker, to
get it so compact you'd ned a vibrating roller, although this is overkill on
a patio.
It doesn't 'set' at all, ever, not that you'd want it to because it needs to
be porous.