Internal waste pipe should it be concreted at the bottom?

Postby Alf58 » Thu Jul 26, 2007 2:13 pm

We have an internal soil pipe that goes into the loft and vents at the centre of the roof. Inside the living parts of the house it is boxed in with a fibre board box.

On ground floor level I noticed a damp patch appearing at the bottom of the boxing in just above the skirting board. There is an inspection hatch just above the skirting where part of the fibre board has been removed and then replaced using screws to keep it in place.

Upon removal of this hatch I noticed the soil pipe goes down into a mixture of sand and soil inhabited by ants. Isnt this supposed to be concrete? The rest the ground floor of the house in concrete. There is no obvious sign of a leak from the soil pipe and there is no smell. Could the damp be rising through the earth and sand particularly with all the heavy rain we've all been having.

How do I solve this problem? Dig out all the rubbish and try to concrete round the pipe? Dig it out so far and then put plastic sheeting down? I just not sure what to do. Hope you can help. The house is about 30 years old.
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Simply Build It

Postby htg engineer » Wed Aug 08, 2007 8:59 pm

Sand will hold the moisture, so that why you're getting damp patches. It's not very often you get a true case of rising damp, alot of people panic when they see or hear about damp but most problems can be resolved quickly and without costing a fortune.

Sand would have been used because concreting round or over the soil pipe can crush or fracture the pipe with temperature variations and ground movement.

The simplest way is to dig out the sand and line with a damp proof membrane of some sort, and fill with concrete so that the soil pipe is sitting on it. Then this can be left as a void if you wanted and just seal the top with wood, flooring etc
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