No birdsmouth on roof rafters

[Joe Carola]

Re: No birdsmouth on roof rafters

Tim,

Nice work as usual but one question. If you frame all your rafters @ 2' o.c. then why did you frame the tray ceiling @ 16" o.c. ?

Just curious because I've never seen a stick build house with rafters @ 2' centers until I came on to theses forums and knowing that you do it and they sheetrock over the 2' centers but why the tray 16" center?


Tim,

I just looked at your picture again and it seems like 16" center because it's just in between the king commons but the rest look like 2' centers.......sorry still love ya........;-)

[FramerT]

Re: No birdsmouth on roof rafters

After seeing Joe's drawing, I see what you're talking about. I thought yellowfin was making a 'jack-rafter'cut on the bottom instead of a seat. Either way, haven't seen that trick neither.
Hi Tim, long time-no-see.

[Ian Cadell]

Re: No birdsmouth on roof rafters

Joe,
In high wind areas where a connector such as an H10 is required it is indeed a great timesaver not to have to cut the birdsmouth. The ties should be fastened to the plate at layout. There should be a mark on the rafter so that it can be lined up with the plate or tie, otherwise it can be tough to get the hips or ridges straight.
Ian

[Joe Carola]

Re: No birdsmouth on roof rafters

Ian,

So you have to nail the connector into the top plate and then set the rafter into the connector and and line up mark on the rafter even with the outside of the top plate then nail the connector into the rafter. Doesn't sound much like a time savor to me at all compared to scribing a birdmouth and cutting one. and then just setting the rafter down and nailing away and your done.

If it is required from where your from do to wind then you have to do so. I guess all your plans are drawn that way. Do you do this on every house even cathedral ceilings?

[John Harman]

Re: No birdsmouth on roof rafters

Ian,

So if I understand you, you don't cut a birdsmouth at all? How do you hold a 24' or 28' 2x12 10 pitched rafter against the ridge without it sliding away before you nail it? Has to be a PITA. The birdmouth not only makes a good place to nail into the plate, but also keeps the rafter from sliding away when its in the notch even if it's only for a couple of seconds. And when it's long like that, you're thankful for the break.

[Ian Cadell]

Re: No birdsmouth on roof rafters

John,
With long rafters against a ridge it's a pain with or without a seat cut. Generally most roofs here are hips with short ridges and rafters are usually 2x8. On jack rafters it's a one man job. Just nail the cheek cuts on layout and then straighten up the ridge when you nail to the tie. No need to worry about snug seat cuts.
Joe,
I would say that about 10% of the framing is done this way down here. It seemes to be slowly getting more popular.
Ian

[Tim Uhler]

Re: No birdsmouth on roof rafters

Tim,

Nice work as usual but one question. If you frame all your rafters @ 2' o.c. then why did you frame the tray ceiling @ 16" o.c. ?

Just curious because I've never seen a stick build house with rafters @ 2' centers until I came on to theses forums and knowing that you do it and they sheetrock over the 2' centers but why the tray 16" center?


Tim,

I just looked at your picture again and it seems like 16" center because it's just in between the king commons but the rest look like 2' centers.......sorry still love ya........;-)

Joe,

What we did with that ceiling was to layout where the "king commons" would be. We just build those ceilings like they are a hip roof. I figure the commons and hips and start cutting and then someone starts nailing. After the kings are up, we measure the distance between and divide by a number (3 or 4) and then the spacing is equal and it looks pretty.

Here is another pic that shows how it starts once we've framed in a box around the room

http://pic9.picturetrail.com/VOL293/...8/78987242.jpg

http://pic9.picturetrail.com/VOL293/...8/78987328.jpg

[YELLOWFIN]

Re: No birdsmouth on roof rafters

Guys,
Sorry for not posting sooner....I've been away for the New Year. The birdsmouth should have been cut in the rafters according to the plans. The rafters are 2x6 with a 12' span and are toe nailed to the top plate at the outside corner as this is the only spot where the rafter is bearing on. It's unfortunate that the framer did this and I by no means would approve of this method. However the situation is such that the house has been sheathed and roofed before this was discovered. Simpson does make a tie that can be used in place of a birdsmouth but it needs to be nailed to the top plate before the rafter is installed....so that is not an option. Ian is right that an H1 clip can be used and I'm checking this out with the building inspector. I've checked with Simpson and the H1 clip is the only one where they have tested for download and have data that is available. While Simpson does have other clips that are similar in design and heavier there is no download test data as all these type of clips are rated for uplift and lateral force. The download data is necessary so I can calculate the force tranfered from the roof load to the clip and evaluate it's capacity for the job.

[Ian Cadell]

Re: No birdsmouth on roof rafters

Fin,
Never thought of the download. Couldn't that be overcome by a close fitting wedge between the rafter and plate. Maybe use a dab of glue? What about the adjacent ceiling joists?? If the rafters are well nailed to them the nails alone should be enough for the load I would think.
Ian

[elijah-c]

Re: No birdsmouth on roof rafters

I was thinking the same with the wedge. If you put a wedge in then it is pretty much the same assembly that most truss manufacturers use, but without the bottom cord of the truss. If you aren't comfortable with using only glue make a plywood gusset for each side also.

[Joe Carola]

Re: No birdsmouth on roof rafters

Yellowfin and Ian,

What makes you think the H1 and the H10 will work when Simpson shows the rafters with a birdsmouth?

http://www.strongtie.com/products/connectors/h.html

[Tim Uhler]

Re: No birdsmouth on roof rafters

Elijah,

It may be a good idea too not to blast nails through the gusset and split it. It may be better to use a smaller shank nail. I don't know.

Joe,

It seems to me that uplift is not the only issue here. Code requires 1 1/2" minimum bearing for load transfer which is a 100% safety factor (according to Will's book). If the rafter doesn't now have a birdsmouth, how can it transfer the load properly? The H1 and H10 don't seem to be intended for that use, although the nails may help enough that it may work in some cases.

I just am not comfortable with this way of cutting a roof. It flies in the face of intuition.

[FramerT]

Re: No birdsmouth on roof rafters

Would anyone put bevels on your door jacks and have the header bearing on the points?? Same concept.

[Tim Uhler]

Re: No birdsmouth on roof rafters

Would anyone put bevels on your door jacks and have the header bearing on the points?? Same concept.

Tiz,

After you told me all the "cool framers cut bevels on their door jacks" I started doing it. I feel pretty cool too :-)

Good illustration. I hope you are staying warm. It's been in the mid 20's here and we may get snow this weekend.

[Andrew R.]

Re: No birdsmouth on roof rafters

A little off the topic but a lot of framers for many years are framing crawl space houses on piers cantilevering the girders 5 " past the pier and cutting the girder on a 45 degree angle, Mason comes in later and installs brick skirt and clips off almost all of brick at that area. Many times they can just spot some mortar there. Entire house ends up sitting on a point of wood. I have seen thousands of houses framed here like this. I have always hung the girder out (cut square)and false blocked the rest of the floor system. This goes on in 4 different cities and I have never seen an inspector fail it. I guess if you can do this you could not cut a birdsmouth. Worked with a guy from New York , he called them boidsmouths.