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The house that we are framing now uses knife plates to attach the rafters to a steel ridge. The ridge is a W16 x45 about 30’long tieing into another W 16 x 45. The beams are supported by a steel column, a wood post and a masonry chimney. The two roof pitches that I am working with are 8.5/12 and 6.57/12. I have no idea why the architect doesn’t use whole numbers for the pitches. The rafters are 6×14 doug fir timbers at less than 4′ on center. The first layer of roof sheathing is 2 x6 T&G pine. On top of the pine is a 7 1/2″ super insulated roof.
The ridge beams will have 10″ x 10″ x 1/2″ plates welded to the web at about 4′ on center. The plates are all perpendicular to the beam. Each rafter will have a top plumb cut of 6.57/12 or 8.5/12.
the top of the rafter flushes out with the top of the steel beam. To attach the rafters to the ridge a vertical slot needs to be made in the cut edge of the top plumb cut. The knife plate will have two predilled 13/16 holes in it. One above the other. The top end of the rafter will be predilled and to accept the 2 bolts to make the connection. The bolt will be countersunk and the holes will be plugged.
I have done knife plate connections before by drilling holes for the length of the plate and cleaning it up with a pratzie saw or chain saw. I have also made template for the bolt holes. It is always difficult to me the connection with the bolts.
I have to make over 60 of these connections. Is there a tool that will cut the kerf in the rafters? Does anyone know of a faster and better way to do this then the method we have used before?
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This tops any hair brained scheme that I've gotten involved with. Barring a specialized piece of equipment from the timberframe world ( maybe a chain mortiser of some type ), I think your method is practical.
I can't really offer any advice but I would love to hear more about or see pictures of the job.
Tom
*Tommy,I took your advice and checked into the chain mortiser. I talked with one salesman from Mafell. The tool is too expensive to purchase unless I were using it daily but they may rent one out.We will more than likely go with the drill and chainsaw technique.Thanks for the helpDave
*How about a large bandsaw? Make two parallel cuts and knock out the waste. A local wood shop here has one with a 3 inch wide blade that I used when I had to cut out a shallow curve in a several beams for a certain effect. That bandsaw went through my beams like a hot knife through butter. I think I paid the guy who owns the shop about $15 for the use of the saw and he helped, too.
*Dave,I'm still curious about the job. Lets hear some gory details.How many square feet? Why a thirty foot structural ridge? Whats the second piece of steel doing? Why steel and knife edge connections? What part of the country?This would certainly classify as oddball stuff in my area and I would love to get a crack at it.Tom
*Tom,The house is about 9000 f. It is in a gate community in Colorado. The second piece of steel is also a ridge. There are also valleys and hips joined to the steel with knife plates.The house has three different roof systems. It has scissors trusses in one area, 14" TJIs in another area and the steel and 6x 14 in the last area. Once past the exterior walls all the rafter tails are the 6 x14. They tie back into the trusses or are false and attached and hung from the soffit with screws. The fascia is above the 6x14s. At the TJI part we sister 2x8 to the TJIs. The 2 x8 go past the building for the overhang. the soffit goes below the 2x8s. Fascia goes on the ends. The 6 x 14 false tails go below the soffit and are held by screws from above. The connections on this house are the difficult part. Besides the connections it is not overly difficult-just large. This house do not have the amount of valleys and hips that we typically see. The last home we were on had over 30 hips and valleys and three round dromers-one was a bay. That house was fun to frame. We were there for more than four months.Ralph, the band saw would work but I doubt the architect will allow the bottom of the rafters to have the cut in them. The roof is exposed from below.
*We were waiting a while for the timbers to come in. Now they are here and we have a few rafters up. The knife plating is slightly easier than I had thought. The kerf for the steel is cut with a large 10" Skill saw. Two cuts are made to let in the steel. The cuts are stopped just above the bottom of the rafter. The cut is then cleaned up and deepened with a chain saw.The drill holes are made first with a 1/4" bit in a drill mounted to a drill guide that has rails. After the 1/4" hole is made the countersink holes are made on each side using a 2 1/8"bit. Finally the hole is finished with a 13/16 bit.I'll be happy when this project is over. The 6 x14 rafters are back breakers.
*Hate to sound dumb, but what's a "knife plate" ?
*Ron,I thought it was pretty clear in his original post.Shall I post a link for you. They must be working you pretty hard at the truss plant.Just busting your balls,Tom
*Ron,The knife plates are pieces of steel with holes in them that fit into a kerf cut into the plumb cut of the rafter. They are not seen at all after the rafter is in place. The bolts then pass thru the rafter and the plate making the connection.
*Thanks, Daved. Your explanation was quite a bit better than that other one.................(-:
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The house that we are framing now uses knife plates to attach the rafters to a steel ridge. The ridge is a W16 x45 about 30'long tieing into another W 16 x 45. The beams are supported by a steel column, a wood post and a masonry chimney. The two roof pitches that I am working with are 8.5/12 and 6.57/12. I have no idea why the architect doesn't use whole numbers for the pitches. The rafters are 6x14 doug fir timbers at less than 4' on center. The first layer of roof sheathing is 2 x6 T&G pine. On top of the pine is a 7 1/2" super insulated roof.
The ridge beams will have 10" x 10" x 1/2" plates welded to the web at about 4' on center. The plates are all perpendicular to the beam. Each rafter will have a top plumb cut of 6.57/12 or 8.5/12.
the top of the rafter flushes out with the top of the steel beam. To attach the rafters to the ridge a vertical slot needs to be made in the cut edge of the top plumb cut. The knife plate will have two predilled 13/16 holes in it. One above the other. The top end of the rafter will be predilled and to accept the 2 bolts to make the connection. The bolt will be countersunk and the holes will be plugged.
I have done knife plate connections before by drilling holes for the length of the plate and cleaning it up with a pratzie saw or chain saw. I have also made template for the bolt holes. It is always difficult to me the connection with the bolts.
I have to make over 60 of these connections. Is there a tool that will cut the kerf in the rafters? Does anyone know of a faster and better way to do this then the method we have used before?