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Running Pipes Under floors

The usual method of laying pipes for floors is to conceal them underneath timber flooring.  The only thing you have to be really careful about with this is to keep them clear of nails that are often protruding from the woodwork under the carpets.

The pipes must be run not less than two inches below the tops of the floorboard joists and below the mid-points of the boards rather than where they join up.

In the case of the pipe runs, being in line with the joists the pipes can simply be clipped to the sides of the joists.  Where the pipes are at right angles to the joists it gets a bit trickier because you will have to cut semicircular notches in the tops of the joists to take the pipes, or alternatively drill round holes directly through the joists for them.

When drilling holes in the joists you have to aim for a compromise.  On the one hand, the hole must be kept as small as possible so as not to weaken the joist, and on the other, you have to ensure that it is ¼ inch wider than the pipe it is taking to give it room for movement and expansion.

It is important to lag the pipe properly if it is being run through an attic space or beneath a timber ground floor, to prevent it from freezing in colder weather.

When fastening pipes to parallel joists, use pipe hangers, and nail timber offcuts back in place after cutting notches in joists at right angles to pipes.

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