Splice underarm truss

[dossanftw]

Hello experts,

I'm in the process of moving my kitchen and encountered a problem when I had to drill through the ceiling for the exhaust duct, and of course, there was a roof truss in the center of the hole (160mm duct). A carpenter suggested cutting off about 20cm of the bottom chord of the truss and "splicing" it from one side with a longitudinal beam of at least the same dimension (see image). If I then move the hole outward corresponding to the thickness of the truss, I'll just manage within the hood's cover. Structurally, it shouldn't be a significant issue since the nearest wall is so close that the truss is supported by it. What do you think about this solution? The center-to-center spacing of the trusses is about 110cm, the house was built in '57.

 

[Plupp 405730]

That is how you ensure that the joint tab is properly aligned in length and screwed well.

 

[dossanftw]

Hello experts,

I am in the process of relocating my kitchen and encountered a problem when I tried to drill a hole through the ceiling for the ventilation duct, of course there was a roof truss in the center of the hole (160mm duct). A carpenter suggested cutting off about 20cm of the lower chord of the truss and "splicing" it together from one side with a longitudinal beam of at least the same dimension (see image). If I then move the hole out equivalent to the truss's thickness, I can just stay within the fan's cover. Construction-wise, this supposedly wouldn't cause any major issues since the nearest wall is close enough for the truss to use as support. What do you think of this solution? The center-to-center spacing of the trusses is about 110cm, the house was built in 1957.

That's how you do it, make sure the splice connection extends sufficiently in length and is well screwed...

Thanks for the response! You mention sufficiently in length, I found a scrap piece 45x120 in the basement that's about 1.7m long, is that adequate? The lower chord of the truss has dimensions of about 50x120.

 

[Isakare]

Thanks for the reply! You write thoroughly in length, I found a scrap piece 45x120 in the basement that is about 1.7m long, is that sufficient? The rafter's lower arm has dimensions of about 50x120.

That will work perfectly.
The lower arms for the garage I built were joined in the middle with 2 boards 22x120, 60 cm long, one on each side, and that was according to the design of the truss that had a span of 6.5 meters, W. Attached with glue and nails.

 

[dossanftw]

Works excellently.
My garage's lower arms that I built were spliced in the middle with 2 planks 22x120 60 cm long, one on each side, and this was according to the design of the truss which had a span of 6.5 meters, W. Attached with glue and nails.

The reason I started the thread is that I can't have planks on both sides, one side is blocked by the vent. The lower arm of the truss will also be missing about 20 cm in the middle. I am attaching the image again so you can see how I was advised to do it, it's hard to explain in text.

 

[Isakare]

The reason I started the thread is that I can't have boards on both sides; one side is blocked by the exhaust duct. The bottom chord of the truss will also lack about 20 cm in the middle. I'll attach the picture again so you can see how I was advised to do it; it's hard to explain in text.

I understood you perfectly and just described a much weaker splice as a comparison.
1.7 meters over 20 cm is more than enough.