Two-story house built in '78. Planning to renovate the bathroom on the upper floor, and the drainage pipes are drawn under the lightweight beams, resulting in the ceiling in the hallway (which is on the ground floor directly below the bathroom) being lowered by 15-20 cm. Since the ceiling on the entire ground floor has now been torn out for various reasons I won't go into, I thought, when renovating the bathroom, to run the pipes through the lightweight beams and regain the full ceiling height in the hallway.
So, how large holes in the masonite is it safe to make? I would need to run a 100mm ventilation duct + 1 drainage pipe (which collects toilet, bath/drain, and sink). It shouldn't be a problem to do this if you place the holes reasonably close to one end of the beam, a bit apart from each other (say 30 cm), and make round holes in the middle of the masonite?
So, how large holes in the masonite is it safe to make? I would need to run a 100mm ventilation duct + 1 drainage pipe (which collects toilet, bath/drain, and sink). It shouldn't be a problem to do this if you place the holes reasonably close to one end of the beam, a bit apart from each other (say 30 cm), and make round holes in the middle of the masonite?
The idea that you can make holes in load-bearing parts at the supports is something that circulates here on Byggahus. I saw similar reasoning the other day.
Sure, the bending moment in a simply supported beam is highest in the middle, but in return, the shear forces are highest near the supports.
Even if the bending moment is often the determining factor when choosing a beam, one must still consider the shear forces.
Cutting into the web of load-bearing beams is not something you should attempt without having an engineer look at it.
Sure, the bending moment in a simply supported beam is highest in the middle, but in return, the shear forces are highest near the supports.
Even if the bending moment is often the determining factor when choosing a beam, one must still consider the shear forces.
Cutting into the web of load-bearing beams is not something you should attempt without having an engineer look at it.
Here is a guide about this, maybe not the same brand of beams but it at least gives an estimate of what you can do for drilling holes.
You can always splice with 12 mm byggplyfaremsor where you place the hole, i.e. screw them into the flanges.
You can always splice with 12 mm byggplyfaremsor where you place the hole, i.e. screw them into the flanges.
Well, but the life in a light beam is technically not load-bearing in the same way as a solid wood beam. The masonite is there to keep the joists the same distance from each other, which is why making holes in a light beam doesn't weaken the beam nearly as much as if an equivalent material had been removed in a solid beam calculated for the same load.Locke said:
Another annoying thing is that there will be many small pieces of pipes you need to pull...
But it might be worth it, like putting down 55 cm ventilation pipes between the beams, slide them to the side through the hole, insert the nipple, insert the next 55 cm piece into the next beam, and so on...
But it might be worth it, like putting down 55 cm ventilation pipes between the beams, slide them to the side through the hole, insert the nipple, insert the next 55 cm piece into the next beam, and so on...
Splice with plywood sounds like a good lifeline, even though the holes will meet the dimensional requirements with a good margin as it seems. I will probably still brace up extra beams between the ones already there to get enough stiffness in the floor for tiles.
Not "technically load-bearing"!? Well, guess what forces want to push the lower flange through the web up towards the upper one?hevi said:
A lightweight beam is nothing other than a two-flanged beam with a web, just like any I-beam. The web has the same significance for bending resistance as in any beam.
Yes, I've thought a bit about that, but I think I'll manage very well with the new layout - there will only be one or possibly two beams where I'll need to drill holes since the sewage pipes from everything except the floor drain go into one of the bathroom walls (just decided on a wall-mounted toilet because of thatJOW said:
).It could have been done afterwards with...
Don't let that sour the whole thread...
It's possible to make holes, you can follow instructions, it can be reinforced.
It's basically the same possibility for drilling as in a regular wooden beam.
Don't let that sour the whole thread...
It's possible to make holes, you can follow instructions, it can be reinforced.
It's basically the same possibility for drilling as in a regular wooden beam.
A lightweight beam and a regular beam function the same way, but the amount of wood material is reduced when making the lightweight beam. However, if you need to heavily load the beam, it must be reinforced in the web, i.e., insert a piece of "regular" wood or structural plywood.
If you drill the holes in the middle of the web, they can be quite large without having an effect. The only thing for the web is to keep the flanges at the same distance and to be stiff enough to prevent buckling of the web. The greatest stress on a beam is furthest away from the neutral axis, where the stresses are highest. However, one must know the shear forces so that the cross-sectional area can withstand them. In this case, it is easy to reinforce on both sides of the hole to accommodate any large shear forces. Simple to calculate using, among others, Steiner's theorem.
Neutrallager is what it's called in Swedish.
In cases like this, the difficult part is not remembering Steiner's theorem from high school but rather estimating the loads, understanding the designer's intentions, and solving the problem better than it was originally done when the house was designed.
Do not cut into load-bearing parts without letting an engineer calculate it - especially not in light beams, as the failure is likely not to be ductile if it collapses.
Have a nice evening, thanks from me!
In cases like this, the difficult part is not remembering Steiner's theorem from high school but rather estimating the loads, understanding the designer's intentions, and solving the problem better than it was originally done when the house was designed.
Do not cut into load-bearing parts without letting an engineer calculate it - especially not in light beams, as the failure is likely not to be ductile if it collapses.
Have a nice evening, thanks from me!
Well, it was indeed a number of years ago that I endured a not insignificant number of points in technical beam theory, but I don't quite agree with you, or perhaps we misunderstand each other (among other things, I didn't say "technically load-bearing" but "technically not load-bearing in the same way").Locke said:
The whole idea of an I-beam is to get as much material as possible as far away from the bending centerline as possible because that's where it does the most good for stiffness (as that's where tension/compression forces in the beam cross-section become the greatest). The web of the beam primarily absorbs and distributes shear forces between the flanges.
One can always try taking up a round hole from flange to flange in a light beam, and then take up a hole with a relatively comparably sized cross-sectional area in a solid wooden beam with equivalent stiffness and load-bearing capacity as the light beam and see which one collapses first.
Yes, I think we are talking about slightly different things here. We have the bending stiffness and strength along the cantilevered part of the beam, but then there is also the stiffness/strength across the beam, such as when the beam is "pinched," for example, between a load-bearing wall on the lower floor and something heavy on top of it. In light beams, the web generally doesn't handle much shear force, so it almost always needs to be reinforced where there are significant pinching forces.peternicklas said: