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I'm re-laying some underground (rainwater) drains. Of necessity these
are laid to a shallower depth than BR recommendations. Also across
location where I park my van.

Building regs recommend that such drains are encased in concrete to
protect against collapse and tree roots.

Usually I would order a polybag of ballast and make up my own
concrete. However it's not a demanding application, no structural
loads, no exposed concrete - do you think Postfix would be up to the
job?

[dennis@home]

wrote in message
...
I'm re-laying some underground (rainwater) drains. Of necessity these
are laid to a shallower depth than BR recommendations. Also across
location where I park my van.

Building regs recommend that such drains are encased in concrete to
protect against collapse and tree roots.

Usually I would order a polybag of ballast and make up my own
concrete. However it's not a demanding application, no structural
loads, no exposed concrete - do you think Postfix would be up to the
job?

No.
Postfix isn't going to stop tree roots, you need dense concrete to stop tree
roots.
You also need strength to prevent collapse.

[sm_jamieson]

On 30 May, 09:40, " wrote:
I'm re-laying some underground (rainwater) drains. Of necessity these
are laid to a shallower depth than BR recommendations. Also across
location where I park my van.

Building regs recommend that such drains are encased in concrete to
protect against collapse and tree roots.

Usually I would order a polybag of ballast and make up my own
concrete. However it's not a demanding application, no structural
loads, no exposed concrete - do you think Postfix would be up to the
job?

I've just concreted part of mine under where a new floor slab will be.
Under where you park your van ? How shallow is the drainage ? If very
shallow, put a reinforced concrete slab over.
If you ensure 150mm around the pipe as I think the regs say, that
should be OK.
Put rebar over the top if you are worried (make sure its surrounded by
50mm concrete). Also, if its a long run, put in some movement joints
(compessible board at a socket junction every 5 metres), since a long
run of concrete can crack due to earth movement and take the pipe with
it.
Surely postfix would be a rather expensive way to do it. Also it may
be a rather weak mix. Why not get some 25kg bags of ballast instead of
a jumbo bag, and add cement to your own strength ?
Having said that, I used a bag of postfix-type product in a plastic
bag last year, and the set surface (streaky grey look) suggested a
very strong mix.
But if you mix your own at least you know what you've got !
Simon.

[Phil L]

wrote:
I'm re-laying some underground (rainwater) drains. Of necessity these
are laid to a shallower depth than BR recommendations. Also across
location where I park my van.

Building regs recommend that such drains are encased in concrete to
protect against collapse and tree roots.

Usually I would order a polybag of ballast and make up my own
concrete. However it's not a demanding application, no structural
loads, no exposed concrete - do you think Postfix would be up to the
job?

If you are using the orange/brown underground drainage, then I would say
don't bother with any concrete - I once used three12 inch sections of this
to move a 1.5 tonne steel girder 200 metres, so unless your van has 18 or
more wheels, they ain't gonna collapse, and therefore no tree roots will get
in.

If OTOH you are using clay pipes, then you would be better off mixing your
own concrete