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Rafter Spread

MelissaB_'s picture

 

Hello everyone!

I just got my offer accepted on a home and had the inspection immediately. In the report, was this rafter spread. I've done some research and it is very concerning to me. I'd really appreciate any advise on how this could be fixed and your opinion on if this is a problem I should not buy into. It is a tile roof, if that matters. Thanks!

Melissa, It's tough to tell (post #216321, reply #1 of 20)

Melissa,

It's tough to tell from the photo's alone. Is this a single rafter that has the spread or all of them? Is there any notable sagging of the ridge? If it's just the one rafter I'd chalk it up to somewhat concerning but not a deal breaker.

Hi Steve, Thanks for the (post #216321, reply #3 of 20)

Hi Steve,

Thanks for the input. I really appreciate it! There is no ridge sag or cracks in the walls. It is a total of two rafters. Do you have any tips as to how to tell if the rafter spread is current or if it was a construction defect? 

I'm with Florida on this one (post #216321, reply #5 of 20)

I'm with Florida on this one it was probably sloppy construction when built. Shims wont do anything. You can sister up a new rafter- doesnt have to be the whole length a 5-6ft piece would be fine. It'll take more time to buy the materials than it will to install.

How many are like that? If (post #216321, reply #2 of 20)

How many are like that? If it's just the one rafter I'd guess it was sloppy framing. Usually when rafters spread it's because the ridge is sagging. In that case the spread creates a pie shape rather than being uniform. If it's just the one I'd make the seller fix it then have it inspected again.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Thank you so much for the (post #216321, reply #4 of 20)

Thank you so much for the input. I really appreciate your opinion. It is two rafters total and the seller said they would place a shim. In your opinion, is that enough? And to clarify what you said, if the tile weight was really sagging the roof,  all the rafters would be spreading? 

Only two rafters means sloppy (post #216321, reply #7 of 20)

Only two rafters means sloppy framing but a shim is certainly not a fix. As Steve already suggested a sister rafter is the answer. The last time I had to fix a rafter like that an engineer was involved and he had us use carriage bolts to fasten the sister to the original. 

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Using a small shim that just (post #216321, reply #9 of 20)

Using a small shim that just fills the gap is unacceptable.  The nails can still bend and do not provide the required strength.

A much larger shim can be acceptable if done properly:

  • Shim material is same size as ridge beam/board, 14" or longer.
  • Shim is fastened to the ridge beam/board, extending out equally from both sides of the rafter
  • Fasten the shim to the ridge with the same quantiy and type of nails as the rafter to ridge conneciton. Check the nailing schedule for your local builiding code.
  • Shim must be a tight fit to the rafter end. Re-cut the rafter end if required..
  • Either
    - Toe nail the rafter to the shim/ridge. Use longer nails to properly penetrate both the shim and ridge, or
    - Use a metal rafter hanger, using longer nails on the ridge flanges. Use the proper hanger nails for the rafter side.

Done this way, the rafter loads are transferred to the shim, which then transfers the load to the ridge.  Both the rafter to shim/ridge and the shim to the ridge need fasteners meeting the nailing schedule.   It can be thought of as sistering the ridge, rather than the rafter.

Using a metal rafter hanger is easier and is a better connection.

If using a nail gun, use at least 30%  more fasteners than required by the building code nailing schedule, as nail gun fasteners are not a strong as common ( hand driven)  nails.

If you decide to sister the rafter using only a partial length, the fasteners between the rafters will have to be calculated based on the dimensions used.  There is mechanical leverage involed with this solution.  The connection between the rafter and sister needs to be stronger than the rafter to ridge connection.  You may need engineering approval.

.

On close inspection you MAY (post #216321, reply #6 of 20)

On close inspection you MAY be able to tell if the situation is ongoing or not by looking for "ghost' marks of the rafters on the ridge board.  If the movement is recent the area where the rafters would touch would be a lighter color.

Also, difficult to do in the situation you have, but if you can tell how much of a gap there is between the sheathing sheets at the top, that will give you a clue.  If the gap is fairly small then the rafters can't have moved much.

Regardless, some shoring up of the joints are needed.  A cross-tie bolted in place and tight against the bottom of the ridge board should do it.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

Sheathing (post #216321, reply #8 of 20)

It doesn't appear that the sheathing has torn loose. This would suggest a construction defect rather than a failure. I'd use a piece of hardware to attach the rafter rather than sistering.

Use metal joist hangers (post #216321, reply #10 of 20)

Use metal joist hangers. Shims are useless. Notice that the sheathing may not have been nailed to the ridge board. Check the tie/top plates of the wall to see if they have moved (possibly due to the lack of proper ceiling joist framing. You can do this by holding a level of the wall just below the offending rafters. A visual inspection and/or a straight edge will hopefully give you a clue. To me this looks like shoddy workpersonship.

Mel Fros froscarpentry.com

Is there something out there (post #216321, reply #11 of 20)

Is there something out there larger than what is readily available? I havent seen a metal joist hanger that will span a 2-inch gap. 

Metal Hangers need tight fit (post #216321, reply #12 of 20)

The generally available hangers made of sheet metal require contact between the rafter and ridge for transfer of downloads. The hanger helps with uplift and rotation. 

Heavy steel brackets, of the type used for post and beam construction, can span a gap. Custom designed, and need engineering approval.

I am well aware of what the (post #216321, reply #13 of 20)

I am well aware of what the hanger does and how it works. My point is that there is a 2-inch gap and every hanger I have seen cannot span that amount of air. Is there something larger available or you suggesting a custom made hanger?

This is why I suggested a 2x (post #216321, reply #14 of 20)

This is why I suggested a 2x cross-tie, through-bolted tight against the ridge beam.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

That gap is not 2 (post #216321, reply #15 of 20)

That gap is not 2 inches...compare the gap to the width of the 2X ridge board.

Its barely 3/4 of an inch. 

yeah.. (post #216321, reply #16 of 20)

The pic so showed a far less gap than that i lost interest in that post right off.

.

It’s a little crazy that (post #216321, reply #17 of 20)

It’s a little crazy that this gets 14 posts deep without a single critical thought given to what was stated.  A 16 penny nail is 3 1/2 inches long. Subtract the width of the ridge board because it doesn’t appear they at toe nailed and that leaves you 2 inches of nail. left. If the gap were two inches, that rafter would be hanging by a thread.

I don't see that the OP ever (post #216321, reply #18 of 20)

I don't see that the OP ever said the gap was 2 inches.  I think she was referring to the ridge board which she called a header. It looks to me like 3/4" at the most.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.

Hang? (post #216321, reply #19 of 20)

Rafters don't hang from a ridge board at all. The roof is a triangle. Gravity loads push down on the ridge.  This forces the rafters apart at the walls. Ceiling joists or collar ties prevent this. Ignoring the sheathing for a moment, if there were no nails at all at this defective joint, the rafter would just piviot at the wall until it hit the ridge. It would be slightly low, but that's all. If anything the nails are holding the joist away from the ridge. Structurally what is need here is not to hold the rafter to the ridge, but to hold it away from the ridge. 

I think everyone understood (post #216321, reply #20 of 20)

I think everyone understood that from the first post. No one referred to it as a ridge beam but as a ridge board.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.