Hi!
I am renovating a log house from the early 1900s.
I am in the process of installing new radiator and water pipes and now need to go through some load-bearing timber beams, quite large in dimension. I will likely run a 20mm PEX RIR to the distributor, which means I need to drill two 35mm holes in the beams. I am now very unsure if this will affect the load-bearing capacity in any way. Does anyone know how much you can drill out before you need to be concerned?
Take care
I am renovating a log house from the early 1900s.
I am in the process of installing new radiator and water pipes and now need to go through some load-bearing timber beams, quite large in dimension. I will likely run a 20mm PEX RIR to the distributor, which means I need to drill two 35mm holes in the beams. I am now very unsure if this will affect the load-bearing capacity in any way. Does anyone know how much you can drill out before you need to be concerned?
Take care
Diversearbetare
· Göteborg
· 11 239 posts
Depends on the thickness of the beam, how far from the ends you drill, and if there is any additional point load from above.
Hi,
Generally speaking, you have to drill quite a few holes before it makes any difference... As long as you can place the holes in the middle of the beam (vertically), it doesn't weaken it at all since a few holes in the middle core of a floor beam do not contribute significantly to the bending resistance. Feel free to check how a steel truss is made as a comparison and you'll find lots of light holes in the middle, but place the holes in the middle since they hardly weaken the bending resistance but do make the construction much lighter and thereby capable of carrying more load.
Generally speaking, you have to drill quite a few holes before it makes any difference... As long as you can place the holes in the middle of the beam (vertically), it doesn't weaken it at all since a few holes in the middle core of a floor beam do not contribute significantly to the bending resistance. Feel free to check how a steel truss is made as a comparison and you'll find lots of light holes in the middle, but place the holes in the middle since they hardly weaken the bending resistance but do make the construction much lighter and thereby capable of carrying more load.
Hey!
Thanks for the response.
I forgot to mention that it's on the upper floor that I will be running the pipes, the beams are about 7.5"-8" and some of these I might be able to drill in the middle of the beam. However, some I will have to carve out from the top. Approximately how much can you carve out of such a beam before it is significantly weakened?
It's difficult to determine what loads are bearing on these. They currently run from the outer wall to the partition wall, and one beam rests on a large blocking (Header) if you can put it that way.
Thanks for the response.
I forgot to mention that it's on the upper floor that I will be running the pipes, the beams are about 7.5"-8" and some of these I might be able to drill in the middle of the beam. However, some I will have to carve out from the top. Approximately how much can you carve out of such a beam before it is significantly weakened?
It's difficult to determine what loads are bearing on these. They currently run from the outer wall to the partition wall, and one beam rests on a large blocking (Header) if you can put it that way.
Jabba77, is it possible to take a picture and upload it so we can get a better idea of what you're trying to do?
If you want to know exactly, a beam that is 200x200mm will have a moment of inertia of 13333cm^4. If you remove about 35mm from the top, the same moment will be 7486cm^4. You have thus weakened the beam by about 44% when calculating the flex the beam will provide. This only matters if you make the cut in the beam where the moment on the beam is large, i.e., right between the supports. If you make the same cut in the middle of the beam, you weaken it by about 0.5% instead.
So, if you have to make a cut on the beam, do it near a support where the load (moment) is as small as possible.
If you want to know exactly, a beam that is 200x200mm will have a moment of inertia of 13333cm^4. If you remove about 35mm from the top, the same moment will be 7486cm^4. You have thus weakened the beam by about 44% when calculating the flex the beam will provide. This only matters if you make the cut in the beam where the moment on the beam is large, i.e., right between the supports. If you make the same cut in the middle of the beam, you weaken it by about 0.5% instead.
So, if you have to make a cut on the beam, do it near a support where the load (moment) is as small as possible.
However, if beams happen to be continuous over the supports, the moment is actually largest right there. Even significantly larger than in the field!d_nilsson said: