Safety issue - gas and water pipes on top of joists!

[Dave Matthews]

Hi folks,

My brother and I were recently lifting some chipboard flooring in my house in order to lay a new electrical cable. Because the chipboard was tongue & groove, rather than ripping out the whole floor, we decided to use a circular saw to just cut out the section we needed to get at. So little bro is happily sawing away when water starts to gush out! What had happened was that rather than running the water and gas pipes through the vertical centre of the joinsts, bl**dy McAlpines had simply cut shallow grooves into the *tops* of the joists and laid the pipes in them. In fact on one particular joist, the grooves were too shallow and caused the pipes to protrude slightly above the top of the joist - hence the chipboard flooring was literally resting on the pipes and I'd been unwittingly walking on them for the last thirteen years!

Anyway we got the leak sorted but I was wondering whether this was common practice in modern construction (my house was built in 1991) as it seems to me to be a literally explosive safety issue!

I have now marked the boards in bright red marker pen to warn whomever buys the property off me!

[Rob Morley]

Maybe next time you'll set the saw blade to the thickness of the floor :-)

[Andrew Gabriel]

It's still done with water pipes certainly. Not seen gas pipes in a new build recently (other than set into concrete floors).

[Dave Matthews]

We did! Well, the boards are 18mm and we set the saw to 19mm, which we thought was a pretty safe margin!

[Rob Morley]

Unlucky :-(

[<me9]

A friend took up a board on his landing, near teh kitchen ceiling. He found a neat row of holes in the gas pipe below, corresponding to the nails in the floorboards. So much for NHBC builders!

[Brian G]

Hi Dave,

To answer the question, yes it is 'normal' to notch the top of the joist for pipes and cables and it's usually done because it's easier than trying to drill a series of holes through the centre of the joists for each pipe and cable - BTW, welcome to the club and the moral of your story - is ALWAYS check before cutting or nailing through floorboards :-)

Brian G

[Rob Morley]

How do you check before cutting when you have to cut the floor to check what's under it?

[Matt]

With a cable/metal detector

[Stuart]

And decidedly tricky to get copper pipe through the holes as well..LOL Stuart

[Brian G]

Ah! Therein lies the skill -- and an educated guess!

The easiest and safest way is NOT to use power tools but to take up a single piece of flooring simply by *gently* cutting through the tongues with a padsaw or a hammer and chisel, lift that piece of flooring and then use the scientific method of 'sticking your head down' to have a good look around - or merely sticking your arm in as far as it will go for (dare I say it) a good feel around. LOL

Oh aye! You could use one of those new fangled metal and stud detectors as long as the pipes are not plastic.

Or the installer(s)/chippies could have left screwed 'traps' somewhere along the length of the pipes or cables that could be pulled up - personally, when I was 'on the tools', I tried whenever possible, to ensure that I screwed the floorboards immediately over the pipe/cables down and marked them.

Brian G

[Dave Matthews]

Well that was the odd thing - there is a set of electrical cables that run close to and parallel to the pipes but they have been fed through holes cut through the centres of all the joists. The new cable I was putting in required us to drill a new series of holes through the joists but it was a doddle to do - about five minutes to drill five holes!

I'm guessing that the gas and water pipes were installed first by one contractor and then another contractor was brought in to do the electrics who decided to do his part of the job properly!

[Derek ^]

It is (or certainly was) specified that way in the wiring regs.

DG

[Ian Stirling]

Will that pick up plastic pipe? Though hopefully it wouldn't be carrying gas.

[Matt]

Hopefully anyone using plastic will have threaded it through the joists rather than notching. I reckon I'd stand a reasonable chance of picking up notches in joists with my stud detector - as long as they were not filled with wood pipes - not tried it though, any thoughts?

[David Hearn]

Were these new holes precisely square to the joist, and were they all at identical points between these 5 joists (ie. you could look through from one end to the other without any deviation or blockage etc).

Feeing 2.5mm T&E through holes in joists isn't difficult, whereas feeding 3m of copper pipe though holes is. Unless you start bending it to get it through the first hole, it's pretty much impossible I think. And, once you've bent it for the first hole, the remainder holes then get a problem. Drilling holes through each joist such that it is square to the joist (and not running up/downhill) and at the same position as the hole in the previous joists is a pain. Notching however is much easier for pipes.

D

[Ed Sirett]

This is certainly against current building regs and may well have been contrary to the regs in force when the house was built. It probably went undetected by the BCO when the house was built.

Using plastic pipe and a right-angled drill putting the water pipe through the centre of the joists is not a big problem.

The gas pipe will be very difficult to correct. Sometimes a hole can be drilled in the wall outside and the pipe pushed through (did that once to avoid putting a pipe outside at the front).

[Brian G]

Not necessarily and certainly NOT when I served my apprenticeship (carpentry) in the mid 1960's. It was a recognised procedure to notch the top of the joists (and there is in fact a formula to calculate the maximum depth of cut (and distance from wall) that can be made without weakening the joist)

Ok as you say with plastic - but a beggar with copper pipe, especially the bigger sizes -and usually impractical anyway.

To contradict this: This is actually very easy (and safe) to correct, just notch the joist slightly deeper and push the gas pipe down into it (as long as the joist is not cut more than a third of its depth [highly unlikely in this case] ) and if worried about the pipe rubbing, just buy a roll of air-felt to put over the top of it.

I would also hazard a guess that even with the pipe touching the flooring, there is no serious (if any) damage to it that has been caused just by 'walking' over it.

[Ed Sirett]

Whilst I certainly agree that notching was standard practice in the 1960s, I'm not sure that whether it was acceptable in the 1991, hence my comments.

[Dave Matthews]

They were square in the vertical plane but as some joists were quite close to each other, we had to angle some of the holes in the horizontal plane - in a "downhill/uphill" manner. They were all at identical points, though.

Yes, I understand that and I can accept the need for a top-of-the-joist notch approach but it still seems utterly irresponsible to make the notch so shallow as to make the pipes so vulnerable.