Gas Pipe Under the Floor

30 Oct 2007
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United Kingdom
I am converting my garage to a dining room and would like/need to reroute the gas pipe from the gas meter (which is in the garage) underneath the floor of the garage/dining room. The floor is currently concrete but will be built up about 190mm with polystyrene/styrofoam (not concreting to save a few pounds (the garage will eventually be demolished and a 2 story extension built which will need a new footing (hence not wanting to spend money on something that will be ripped out 3-5 years down the line).

My plumber is insistent that the ducting for the gas pipe needs to be a special "made for the purpose" duct vented at both ends. I don't have an issue with the venting but wanted to know whether any type of ducting that protects the gas pipe is OK - for example a length of waste pipe?? Or a timber (narrow) box. I also know that the gas pipe must not have compression fittings.

Any thoughts on what is and what is not necessary?
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What floor surface are you putting on the polystyrene? If it's chipboard the gas pipe wouldn't need ducting as such. A slot cut in the polystyrene to take the pipe should be sufficient to form a duct. What's more, since the volume of the duct would be small you wouldn't even need to ventilate. However no harm in putting the gas pipe inside a length of 32mm plastic waste pipe if it makes your plumber happy.

You shouldn't have any joints in the gas pipe within the duct, but if it's more than 3 metres long that could be a problem. It is sometimes possible to buy 6 metre lengths of copper tube which might get you around that problem.
You are right - chipboard...

My plumber won't even contemplate having just waste pipe never mind no ducting!! Cites Corgi regulations...
Cites Corgi regulations...
No such thing as Corgi regulations. It's the Gas Safety (Installation & Use) Regulations 1998 that apply.

However the Corgi manual shows exactly the floor structure that you are proposing (figure 23 (d), page 84 of 3rd revised edition). The copper is shown laid in the insulation layer, resting on the concrete "raft" below, with a chipboard layer above insulation. No duct, sleeving or protective wrapping shown.
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AFAIK it's currently under review since chipboard flooring does not allow the same ventillation as traditional floorboards, however for the time being the existing regs apply.

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