i have just dug a channel in my concrete floor, through the kitchen,
lounge & hall, which is about 6 inches wide, 5 or 6 inches deep, and
10 meters long (sorry for mixing metric & imperial), in order to lay
the downstairs pipework for my new central heating system (i don't
want any pipes/surface conduit boxing visible), and i was just
wondering if any experienced builders out there could tell me the best
method to fill it back in again now all the pipes/conduit boxes etc.
are in place. The original concrete floor is about 4 inch thick, so
obviously i've broken right through this to the loose hardcore/earth
below, etc., so do i use sand, rubble, hardcore, some of the old
broken concrete, just new concrete mix, or am i thinking all
wrong...............all i want is to patch it up as it was before,
with no chance of it ever coming loose/rocking under foot etc.
sorry if this is a bit long winded, hope someone can help.
I only hope your telling us that you've put the copper piping and cables
into a duct of some sort (?) as the chemical reactions between copper,
electricity and the PVC coating of the cables with cement and aggregates in
the concrete will wear them down to the point of breaking within a very
short period of time.
The cable and pipework should be installed through galvanised trunking or
nylon terrain pipe (the red pipe used for underground systems) to stop the
reactions from happening and stop the need for it all to be dug back out to
for more information on this.
You can cover the pipework and cables with a protective layer of roofing
felt before filling, or place heavy duty polythene around them to give a
protective coating, but this will also give rise to the need for a solid
layer to prevent the new concrete from causing the pipes and cables from
bending and breaking at the joints.
If the pipes and cable are directly on to sub soils under the floor, then
this too can cause damage from chemicals in the soil and allows bending due
to the weight of the concrete and people walking over them and the pipes and
cables should be laid on top of a layer of sand to a depth of at least 30 mm
which helps to cushion them.
Please be careful with this, as it may cost you dearly if not done
If you are using plastic pipes just pour concrete. Although I would put
them on a concrete base first just so they are completely enclosed. What
you have done is the normal way of construction on the continent burying
plastic cables and pipes in a concrete screed. The manufacturer of the
plastic pipes should be able to give you some guidance.
However, as everyone has pointed out do not do this with copper pipes, they
react with concrete and expand when heated and will fail quickly.
The plastic pipes will expand even more than copper so will need some kind
of all round space to allow for movement. If you don't allow for them to
expand and contract then your joints will definitley just fall apart.
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