I have just lifted some floorboards to replace them and have discovered that someone has previously notched out the top of several joists to accommodate some CH pipes in a first floor bedroom.
I know this is a difficult question to answer but can anyone tell me how I find out if this is a serious problem and what can be done about it. The house is a 1960's semi if that's any use.
I guess I'll need to measure the sizes of the joists and their spacing, which I will do when the kids aren't in bed!
Are the pipes still in place and in service? How many notches, of what size and how close together? How long have you lived in the property? Is there any sign of bounciness in the floor or displacement of the joists from their original positions (eg a gap opening up between floorboards and skirting)? If so has it got worse during your time in the property? In short, more info needed.
dont worry too much if they arent exactly to this spec, it probably doesnt mean theyre gonna fail, my house has notches and drill holes way beyond the given spec and its as solid as a rock! I've had to comply with regs on the extension though as it's under building regs
It's very common - and not a problem provided the rules have been followed. I can't quote the rules precisely, but the notches must be fairly close to the ends of the joists and mustn't be deeper than a certain fraction of the joist height. I'm sure someone will come along and quote chapter and verse. Joist sizes are based on limiting the deflection of floors, rather than on strength requirements per se - and invariably have a lot of strength in hand. If you are over zealous with your notches, you may end up with a floor which is a bit springly - but it's unlikely to collapse.
The other thing I would think about is popping little bits of steel plate over them as future protection against screws or nails; or if the boards are going to be carpeted, mark the CH pipe runs in permanent marker pen.
Well, they didn't leak much so he didn't notice. I did - and so did his partner - and so did my sister when she came to stay. We all noticed a very faint smell of gas and spent some time sniffing around before deciding it wasn't from our house. It was only when I was about to ring Transco and thought I'd mention it to nextdoor first that I realised the smell was coming from near his front door. You couldn't really smell it in the house, just outside. I guess it was making its way along the floorspace and out through the meter cupboard.
Given they both smoke heavily and cook with gas I guess we were very lucky. It'd been like that for some weeks!
Colleague took up a floorboard on his landing after smelling gas. He discovered a previous bodger had nailed down the floorboard into the gas pipe with a nail at every joist. He'd lived in the house over a year before he discovered it as the nails (almost) sealed the holes.
Every basic primer on 'beam theorty' explains that the majority of Load on any beam is carried through the 'top' and the 'bottom' surfaces. There is a close relationship between the amount and nature of the material in the 'top' and the 'bottom layer', and the distance apart. Consider the shape of a steel I-beam..... Consider the same shape of an 'engineered wooden beam'....... Consider the shape of your floor joists, and recognise that there's quite a lot of wood doing nothing.
Essentially, the wood along the mid-line ( the neutral axis ) is only holding the rest - the stuff doing the work - sufficiently apart. That's where any cutouts and holes for services should go.
Any notcheds and cutouts in the upper or lower surfaces are seriously weakening the joist-beam, and should be repaired. Think of it this way
- would you happily fly your family in an aircraft where cutouts had been made to the wings' mainspar, by someone unknown? No, I didn't think so.
Only a qualified structural engineer could survey and calculate whether there is enough strength left in your joist-beams for the loads that are likely to be placed on them - and that's a costly exercise, with a lot of 'ifs' and 'buts'. Happily, it is both cheap and easy to repair these - go to your local builders' merchant ( or Google ) for a catalogue from Simpson or Expamet, and fix in some repair plates.
The stresses change depending on where along the beam you are, whether they are shear, or tension/compression.
Shear stresses are more significant near the ends, so notches are permitted, but not central holes. Two, pin jointed, triangles would suport the (central) load (under tension/compression), remember timber has different strengths across/with the grain.
If central or excessively deep then yes.
Aircraft are designed to the limits of the materials used. I once had an (educational) project to build an elastic powered 'drag racer' to beat others in the class. the power was limited, the winner had effectively to produce the lightest structure that could remain intact for the race from balsa, fibreglass, resin, piano wire and plastic wheels. mine came second, being heavier (and stronger) than the winner.
How much do they deflect with expected loads? that's a good indication as to whether they are up to the job.
Possibly, if necessary. Other options are to add additional joists (difficult to fit?), or steel reinforcing of some description. If in doubt involve a structural engineer and/or the BCO.
Actually beams in floors are totally overdesigned, so as to achieve STIFFNESS. Not ultimate strength. The STIFFNESS is not actually reduced that much by the odd knot hole or notch.
Sure the floor is weakened, Maybe it will only take 30 tons instead of
50...but the plaster underneath will be long gone before it gives way...
The message from "bilbo*baggins" contains these words:
You serious? I'd say pretty well every house in the land which has had heating pipe retro-fitted to a floor has had the beams notched. How many have had serious structural problems as a result?
While I completely agree with you about how and why the stop layers in a beam are important, you've missed the simple fact that people have been doing this for years without problems.
The message from David Hansen contains these words:
Nah, it's easy - you do it in sections shorter than the distance between the joists and solder up the connections in each bay.
However, see note 13 and ensure that the joists are sufficiently far apart.
1.All pipe is to be made of a long hole, surrounded by metal or plastic, centred around the hole.
2.All pipe is to be hollow throughout the entire length - do not use holes of different length than the pipe.
3.The ID (Inside Diameter) of all pipe must not exceed their OD (Outside Diameter) - otherwise the hole will be on the outside.
4.The pipe is supplied with nothing in the hole, so that water, steam or other stuff can be put inside at a later date.
5.All pipe is to be supplied without rust; this can be more readily applied at the job site. NOTE: Some vendors are now able to supply pre-rusted pipes. If available in your area, this product is recommended, as it will save a great deal of time at the job site.
6.All pipe over 500ft (150m) in length should have the words "LONG PIPE" clearly painted on each side and end, so the contractor will know it's a long pipe.
7.Pipe over 2 miles (3.2km) in length must also have the words "LONG PIPE" painted in the middle so the contractor will not have to walk the entire length of the pipe to determine whether it is a long or short pipe.
8.All pipe over 6ft (1.83m) in diameter must have the words "LARGE PIPE" painted on it, so the contractor won't mistake it for a small pipe.
9.Flanges must be used on all pipe. Flanges must have holes from bolts, quite seperate from the big holes in the middle.
10.When ordering 90 or 30 degree elbows, be sure to specify left-hand or right-hand, otherwise you will end up going the wrong way.
11.Be sure to specify to your vendor whether you want level, uphill or downhill pipe. If you use downhill pipe for going uphill, the water will flow the wrong way.
12.All couplings should have either right-hand or left-hand threads, but do not mix the threads, otherwise, as the coupling is being screwed on to one pipe, it is being unscrewed from the other.
13.All pipes shorter than 1/8in (3mm) are very uneconomical in use, requiring many joints. They are generally known as washers.
14.Joints in pipes for water must be water tight. those pipes for compressed air, however, need only be air tight.
15.Lengths of pipes may be welded or soldered together. this method is not recomended for concrete or earthenware pipes.
16.Other commodities are often confused with pipes. These include; Conduit, Tube, Tunnel, and Drain. Use only genuine pipes.
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