Finding Trusses From Rooftop

[A/A Fuel GTX]

I've got a situation where I need to guy a service mast on a house. Is there any trick to finding the roof trusses on a house where the soffet is enclosed therefore hiding the location of the trusses? Attic access is not an option here. I need to lag bolt the guy wire and want to hit something solid.

 

[infinity]

You can gently lift up a shingle and drill a row of tiny horizontal holes about an inch apart until you hit the roof joist. When done fill the holes with a dab of roofing cement and press the shingle back down.

 

[Smart $]

You can gently lift up a shingle and drill a row of tiny horizontal holes about an inch apart until you hit the roof joist. When done fill the holes with a dab of roofing cement and press the shingle back down.

Before lifting shingle and drilling holes, take a hammer or other blunt tool and rap on the roof across the direction of framing. In between trusses the sound will be more of a thud, while right on the truss the sound will be more of a "thad".

Guess at the center of the truss and drill a hole there. Hit or miss, drill holes to either or both sides until chord edges are known, so you can then position the lag bolt dead center.

Tip: When working with asphalt shingles, I use a heat gun to warm up the bending point of the shingle to make it more pliable (unless shingle is already hot).

 

[fireryan]

you could also find the rafter tails in the soffit by gently pushing up on the soffit untill you hit the rafter. This would get you pretty close and then you could use a 4' level to make a straight line up on the roof

 

[cowboyjwc]

You know that the last one is right on top of the end wall and then they "should" be at 24" on center from there.

 

[hurk27]

You know that the last one is right on top of the end wall and then they "should" be at 24" on center from there.

Or 16" and depends upon which end of the roof they started from

While I'm not a big person by any means, I find them just by walking and seeing where the roof sags as I walk, of course this is in the middle of the roof not at the edges or ridge, but I can straddle one and rock back and forth and see where the deck sheeting pivots on the truss, most roofs here are 7/16ths OSB decking, many newer house roofs are 24" centers, but most older house roofs are 16" centers, Hip roofs can be a pain to find.

 

[Cow]

Would a stud finder work? I can't remember if they sense the depth of wood or simply look for nails(which would make it worthless on a roof!).

I'd probably end up tapping, listening for a thud, and then drilling holes to verify like infinity said.

 

[wawireguy]

If the eves are boxed maybe you can see where the boxing was nailed on to the trusses and measure off that?

 

[cowboyjwc]

Or 16" and depends upon which end of the roof they started from

While I'm not a big person by any means, I find them just by walking and seeing where the roof sags as I walk, of course this is in the middle of the roof not at the edges or ridge, but I can straddle one and rock back and forth and see where the deck sheeting pivots on the truss, most roofs here are 7/16ths OSB decking, many newer house roofs are 24" centers, but most older house roofs are 16" centers, Hip roofs can be a pain to find.

He did say trusses and the norm is 24" centers, but you are correct it could be 16" centers if it's an older house. Here we don't enclose our rafter tails so it's really easy to see where the trusses are.