Large Steel I Beam - Drilling for a waste pipe?

Simes123 · 21 Mar 2012

Trying to overcome a plumbing routing issue for bath and shower waste, caused by a wacking great steel I beam. Can't go under, as the ceiling mounts to a wood casement and it's too early in the run to go that low. Can't go over, as that's just below the floorboards.

Can't box the pipes in as there is window that goes to floor level between the bath/shower and the soil stack (the window spans 2 storeys in a converted church.

I've got two solutions:

1. Build a raised floor across half the room that in effect gives a giant box that enables me to get over the I beam. I've embarked on this adventure, but it seems like overkill.

2. Drill two x 43mm waste holes through the web of the I beam.

I had previously discounted option 2 without too much thought. Option 2 might be feasible though if I could a) find a drill that large to cut through the beam, and b) if doing so would be permissible under building regs.

I'm away from home at the moment, but the I beam is huge - probably 6" wide on the top and bottom, with possibly a 10 or 12" web (working from memory). If I could physically achieve it, could option 2 be a permissible option? It would be aesthetically much better and would uncomplicate a host of other issues I face with the raised floor option.

OwainDIYer · 21 Mar 2012

you'd need a structural engineer to check the beam design still meets regs even with the holes drilled in it.

much as I dislike them, is using a sani-shower to go straight up and over the window an option?

Simes123 · 21 Mar 2012

Thanks. The path of least resistance and least cost then might still be the raised floor. I'm not too averse to it, but thought I'd at least rule out the alternatives. From a (short) bit of reading, it sounds like drilling through the web of hefty I beams seems common practice without undue detriment strength, but in itself may involve the use of plasma cutters etc, which is added complication I don't want given I have the bathroom in bits and the missus is getting impatient with my multiple weekend project!

Deluks · 21 Mar 2012

A hole cutter for metal in a cordless drill will easily go through a web.
Even if engie says no, he could still recommend a solution for strengthening the beam with a plate or such, and would still be cheaper than getting sani-flo fitted.

My bet is that it'll be OK, (if it were me I'd have drilled it by now)

Why two holes though, can't you branch the 2 pipes before they get to the beam?

Simes123 · 23 Mar 2012

I could join the two prior to the I beam, but I would have to make a couple of 90 turns in each waste to achieve it as the I beam is quite close to the bath/shower. I was trying to keep to swept turns as far as is possible which would mean joining the two much closer to the stack on the other side of the room.

Will a holesaw really be man enough to get through a hefty i beam web?

jeds · 23 Mar 2012

Drilling will almost certainly make no difference to the beam as long as the hole is fairly central. The times I have calculated similar holes in beams the difference in second moment of area was very small and nowhere near enough to alter the serial size. However, you should get it checked in case your beam is undersized to start with.

Simes123 · 23 Mar 2012

OK, thanks. I'm happy to get it checked, but I'm worried about cost. Not in absolute terms, but in terms of the cost of having it checked by a structural engineer, him ok'ing it, and drilling, vs building the raised floor. If it's a case of £50, he ok's it, then drilling makes sense. But if I'm going to get a £300 bill, I may as well just do the raised floor.

Any idea (and I know this is difficult) of the cost for a structural engineer to take a look (floorboards are already up), and for him to do the calcs, give me the OK and presumably a letter to say that he's happy?

Tempting that it is to just go ahead and drill the 2 holes in the web, it would give peace of mind to have a structural engineer's blessing. Quite how they do the calcs in practice when they have no idea of the weight being supported, I've no idea!

Simon

Norcon · 23 Mar 2012

Will a holesaw really be man enough to get through a hefty i beam web?

A new one might. I'd run it through with oxy/acetylene.

jeds · 24 Mar 2012

What's the details of the beam and the load? In older houses it's common to find beams that are massively over spec'd just to take a small floor load. They probably didn't calculate anything when it was installed - they just fitted large because steel was cheap. You might be lucky.

djdna2000 · 27 Mar 2012

Builders have just done the same thing in our loft conversion, using a hole saw, 5-min job. I can't see how it would make any appreciable difference to the strength of the beam, many steels are constructed that way anyhow.

leew2 · 27 Mar 2012

Many big warehouses and the like have lines of holes cut in the webs of I-beams to lighten them, most of the load is taken by the top and bottom flanges.

Simes123 · 27 Mar 2012

OK, the beam is about 8" on the flange and 12-14" or so deep on the web(hard to tell exactly as the bottom has been clad to support the ceiling below). Looking further, there is a second parallel beam of the same size, the other side of the window - perhaps about 12ft away (both beams are somewhere around the centre of the house) Both beams appear to span the full width of the house (about 45ft) and have been installed to support the new second floor (the floor didn't exist before conversion). There may be further steel beams at the same spacing, but I can't see without taking the floors up. Both beams here are joined to form an H around the centre of the span. In terms of load - it is supporting the second floor (with 3 bedrooms and a bathroom, and a large Mezzanine area - again, just floor load. All the walls on the second floor are studwork, non-load bearing.

hillbilly63_uk · 29 Feb 2020

You can often drill quite large holes through steel beams before reinforcement is needed. Depends where the hole is and loads etc. This page shows allowable hole sizes (scroll down to see diagram) https://www.smartbuild.uk.com/steel-beam-web-opening-service-hole

bernardgreen · 29 Feb 2020

Not picking holes but this thread is almost 8 years old.

23vc · 29 Feb 2020

bernardgreen said:
Not picking holes

See what you did there...

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Large Steel I Beam - Drilling for a waste pipe?

Similar threads