I’ve pulled up some floorboards on the landing and found what I think look like pretty large notches out of the joists and am not sure if I should be worried or not. We had a new boiler and rads installed about 4 years ago but not sure if the plumber added these notches or used existing ones. No idea when the ones for the electrics were done or why there are 3 holes. This is just one joist and it’s the same all the way across 5-6 joists from what I can see.
From memory, notches for pipes in timber joists should be no more than 12.5% of the joist’s height. ( In this case, being 150mm joists, the notch should be no deeper than 19mm) Don’t quote me, but I think any notches must be no further out than 25% of the joist’s span from the point it is supported on the wall, plus you are not supposed to notch near the supported end either. There are rules about the max diameter of drilled holes, their location and spacing for cables, but you’ll have to research that for the exact data. Looking at your photos, I’m pretty confident that the notches are too deep and should not be located above the drilled holes either. Yeah, the joist in your photo is structurally compromised I’m sorry to say.. plus the pipes should be lagged and/or fixed to stop them rattling.
The holes are OK and clearly pre date the pipes, but the notches..... If it was my house I would be concerned. The span of the joist and the position of the notches along the joist are an important factor to consider.
How far from the wall is that notch and what is the span? Do a Google search for "joist Notches" and look for a British, not US one.
Some plumbers/electricians don’t seem to like following the rules on notching/drilling joists. As mentioned you can strengthen over the notches. This beauty was what I found the plumber employed by the previous owners did to run the pipes to the sunroom they had added! Thankfully it is only one joist and due to the position it doesn’t take much load but is now compromised. The hole in the floor to access this appeared to have been created by chewing the chipboard with this teeth! How the remains of the board he put back in didn’t collapse I am not sure. Plumbing and floor have all been replaced now!
It’s not right but rest assured most plumbers and sparks and anyone else really will either be unaware of the regs on joists or will simply ignore them. For eternity they’ve just cut away or drilled whatever was in the way. Those houses are (probably!) all still standing. It wouldn’t concern me to find that to be honest. Doesn’t make it correct but it’s not going to fall down.
I wouldn't be overly concerned, I've seen worse, much worse. Once discovered a 110mm soil pipe expertly fitted under the floor going through four 9x1.5 joist in the middle of an approx 6mtr span. Had a decent fall on it too. The last joist had about 30mm of timber remaining under the pipe . Had been that way for about 15 years with no detrimental effects.
In my house(100 years old) the joists have been butchered by plumbers and sparks over the years. I’m not concerned and the house is still standing fine. Quite good in a way as it’s been easy to run new pipes in lol.
Thanks everyone for the replies, overall it’s pretty reassuring and I looks like we don’t need to crawl down the landing just in case! Disappointed in the plumber obviously, he was recommended to us and we waited a good few weeks before he was available which I took as a good sign. However, aside from the large notches and lack of lagging also recently found out he’s used too small a pipe for both the gas pipe and rad water pipes. Plus a floorboard he cut in the middle of a joist I had to replace - I only noticed after moving some furniture. @koolpc, you mentioned I might be able to reinforce - is that a simple job for a diyer?