After a second and third look I am going to have to agree with Thomas on this. This sure appears to be a non issue.
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It appears that way to me too. But this brings me back to my question earlier: at what point does it become an issue? when the roof is caving in? everything ive ever read about truss alterations says “DONT DO IT!” it doesn’t say anything about size or severity of alterations. it says none, full stop.
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Well without seeing the full picture of the attic. It does not appear that any of the drill holes are thru the bottom two by four of the bottom cord it appears to be on the top board of this double stacked catwalk. Which to me is an non issue. If it was thru the bottom cord I would agree with you but not with what I see in this picture.
Between you and me, thats a very good point. But that also sounds like a consideration only a SE is qualified to make.
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I think you may have it backwards, IMO, you cannot drill into a rafter ever but some locations on bottom cords are ok.
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I don’t know where you found that Brian but that is for that particular type of truss and is totally useless in this situation.
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If only there was a diagram for where I can drill into trusses… but there isnt. because they are strictly related to the specific truss and requires an engineer to produce.
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Michael its just our opinion and you must be the one to make the final decision in your best interest but we are telling you from our vast experience that this is a non issue. Enjoy.
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Oh yea, I hope I don’t seem like I have a snarky attitutde. I take my work very seriously and I’m just trying to flesh out my thoughts with yall. I really appreciate you all and I understand that
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No it doesn’t seem like that at all . You are just looking out for the best interest of your client. We get that report it and move on. No SE imo.
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oooh, that diagram was specifically about trusses. I thought it was a conventionally framed diagram. That’s actually very helpful. The spacing and sizing of the holes seem okay, but they are not on the center line of the bottom chord.
No that is specifically for attic trusses and is irrelevant in this situation.
oh dang it
Those are not “Standard Trussed Rafters”…IMHO.
See gusset connection of 2x6? above 2x4?
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Engineered roof truss design software lists the Combined Stress Index (CSI) which is the total of axial and bending stresses as a ratio of allowable stress in truss members. The CSI ratio can be up to .99.
Maximum CSI is shown on the example truss design drawing below. In this truss the Bottom Chord (BC) has a CSI of .75 or the bottom chord in this design is only stressed to 75% of its maximum strength. Most truss designers would not go above 95% to allow for natural occurring defects in wood.
The number, size and orientation of the holes makes a difference. In the example below the two 3/8" holes reduce the cross section by 11% at each location, however if the two holes align vertically then there is a 22% loss in the cross section. So truss plans , hole sizes a orientation is needed, but It’s a judgement and/or liability call for the engineer to make. The IBC and IRC both include specific requirements prohibiting unapproved alterations to trusses.
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Looks like the CSI is a very important number in this case.
I have a question.
Is this talking about deflection?
I just inspected a home and called out truss rafter sagging. Is there an acceptable tolerance for some sagging or deflection?
Here is the photo, though it is always hard to “catch” sagging in a photo.
I don’t think anyone is disagreeing with this Randy. However the OP’s question appears to be about the board above the bottom cord. Would you agree that this is a non issue?
If you look closely at the photo there are two bottom chord members connected with metal truss plates. This could be the bottom chord on an attic truss or some other reason this bottom chord was carrying a heavy load.