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-   -   gap between ridge beam and ridge board (http://www.diychatroom.com/f19/gap-between-ridge-beam-ridge-board-70691/)

mdudu 05-06-2010 09:11 PM

gap between ridge beam and ridge board
 
I am creating a vaulted ceiling over my living room in my current renovation. To support the roof when the joists are removed I am adding a engineered lumber ridge beam under the 2x8 ridge board used as a nailing surface for the rafters.

The beam only needs to span about 13 feet but even in that short distance the ridge board either was bowed or it has sagged. Either way the result is that when the new ridge beam is pressed up agains the current ridge board, there are long gaps from either end to the low point. The low point is closer to one end than the other so the two gaps go from 1" to the touch point on one side and .25" to the touch point on the other.

How do I deal with this gap? Should I cut a long piece of wood and squeeze it in between? Or use separate blocks at different places (maybe aligned with the rafters) rather than one continuous piece?

Any ideas?

Thanks!

Andrew

Willie T 05-06-2010 09:58 PM

3 Attachment(s)
You deal with it by TAKING THE SAG OUT.

Make certain the ends of the BOARD are fastened down securely so they will not move upward when you do the following....

Put the BEAM into position, then place a jack under each end... far enough out from the ends so you can insert a support without having to take a jack out. Start jacking... slowly and evenly

The center... BOARD and rafters, both... WILL start moving upward. When the BOARD gets level all the way across, put in hefty supports for each end under the BEAM, and remove the jacks.

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I'm assuming you have already made provisions for 'seats' in the top ends of the rafters for them to sit down on top of the BEAM? And how are you going to get the BOARD out of the way? (assuming it hangs down below the bottoms of the rafters)

You are aware that you will accomplish nothing (or very, very little) if the rafters do not sit down on level 'bird's mouth' cuts on the top surface of the BEAM? To get around this, you would need to install fairly heavy metal brackets bolted through both the BEAM and the tops of each rafter.... that is, IF you had in mind to be fastening these rafters to the SIDES of the BEAM.... which is usually not cool on an engineered beam.

mdudu 05-07-2010 08:56 AM

Hi Willie,

That was extremely helpful, thanks very much for the diagrams. The current plan is to leave the ridge board in place and have the ridge beam support that directly and the rafters indirectly. The rafters were originally just toenailed into the board and now have metal connectors (L-brackets on either side) holding them against the ridge board. There are also going to be horizontal 2x6's coming out from the ridge beam to every third set of rafters for additional support and to provide bracing for the beam to prevent it from flopping horizontal.

Andrew

tpolk 05-07-2010 09:22 AM

Quote:

Originally Posted by mdudu (Post 438677)
Hi Willie,

That was extremely helpful, thanks very much for the diagrams. The current plan is to leave the ridge board in place and have the ridge beam support that directly and the rafters indirectly. The rafters were originally just toenailed into the board and now have metal connectors (L-brackets on either side) holding them against the ridge board. There are also going to be horizontal 2x6's coming out from the ridge beam to every third set of rafters for additional support and to provide bracing for the beam to prevent it from flopping horizontal.

Andrew

this is exactly the correct way to handle this. willies way is perfect but not needed. you can shim gaps at rafter bearing points

tpolk 05-07-2010 09:26 AM

the harder the shim material the better

kwikfishron 05-07-2010 09:59 AM

Why wouldn’t you jack it up? The beams up there. If the ridge is drooping a inch on the inside you know it’s doing the same thing on top. It all can be fixed in the same time or less than dealing with shims.

Gary in WA 05-07-2010 09:46 PM

What did your building inspector say about putting a structural ridge beam under a ridge board? What connections are required to hold the rafters to the beam, not board? If other than rafters notched to bear on a beam or rafters in hangers abutting a ridge beam, you need engineering. How did you figure the loads and forces (snow, wind, seismic, etc.) for the footings and posts for the now structural ridge? A few collar ties on top of the new ridge won't do....... Just trying to keep your family safe.....

Be safe, Gary


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