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Bird's Mouth/ Heel Cuts in stick built roof framing

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#21 · (Edited)
DEAD_ONConst said:
Do you cut your rafters BEFORE or AFTER you set the RIDGE?
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Rafters are all cut first and then the front and back rafters on each corner are set nailed into the top plate and then the ridge gets lifted up and slid in between the plumb cuts of the rafters. No need to set the ridge first t all.

The rafters set the ridge height.
 
#22 ·
Everything depends.

When I am working alone...I calculate everything and set the ridge on legs then I can install the rafters, el-solo.

With a crew, its faster to raise 4 outermost rafters and hang the ridge from them, then brace and fill in.
 
#23 ·
DEAD_ONConst said:
Do you cut your rafters BEFORE or AFTER you set the RIDGE?

I ask, because I did a job, after the ridge was set, some of the rafters were notched for a 2x4 plate, which gave the correct pitch, but after I cut the rest, for a 2x6 plate, which was already there, well, you can imagine, my rafters were LOWER and at the wrong pitch.
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I just read this over again and I didn't answer you in my last post addressing that issue. I thought you were talking about new work. It sounds like you were either tying into an existing house or this was a new frame with a 2x4 wall and 2x6 wall with rafters sitting on both walls and you changed the seatcut or H.A.P cut on the rafters sitting on the 2x6 wall.

If you already had an existing ridge with rafters sitting on a 2x4 wall already and you cut your new rafters for a 2x6 wall, that could've been your problem.

Regardless of what width the wall was if you were trying to match an existing roof, your H.A.P cut should've matched the existing rafters

If your doing new work and for some reason you want to set the ridge, you have to know the exact ridge height to do so. Cutting the rafters which ever way you do them whether using a framing square or calculator is always done first regardless if you set the ridge first or after you lay out your rafter.

If you know how to figure out the exact ridge height and you set it first and then lay out your rafters(not measuring from the ridge and down) using a square or calculator and they don't fit, you either did something wrong with the framing square or calculator, or you set your ridge height wrong.

Can you explain more in detail of what happened?
 
#24 ·
Joe--

What it sounds like to me is he had a 2x4 wall and 2x6 wall and measured to the outside of each, or maybe the inside, and the cut the rafters with a full bearing seatcut.

Maybe the original had 2x4 walls and the addition had 2x6 walls, anyway the HAP's wouldn't match if he went with the full bearing technique.

For the OP, You don't always have to follow the full bearing rule. 3 1/2" of bearing on a 2x6 wall is fine. Most of the time I use less than that. I'm happy with 2" on a 2x6 rafter.

When framing roofs, all your plate heights should start with the thinnest wall, widest stock and steepest pitch. Everything else gets calculated from there.

JK
 
#26 ·
big steve said:
I do it exactly like joe described.If the walls are not perfectly level and paralell it can be a little tricky or if the rige beam has to big of a crown. I still cut em all the same and make them fit. Steve
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I always cut the crown out of the ridge board:thumbsup: I'm giving thought to useing a rim joice for the ridge on a sunroom coming up soon.
 
Discussion starter · #28 ·
Rafters and Ridges

Joe Carola said:
I just read this over again and I didn't answer you in my last post addressing that issue. I thought you were talking about new work. It sounds like you were either tying into an existing house or this was a new frame with a 2x4 wall and 2x6 wall with rafters sitting on both walls and you changed the seatcut or H.A.P cut on the rafters sitting on the 2x6 wall.

If you already had an existing ridge with rafters sitting on a 2x4 wall already and you cut your new rafters for a 2x6 wall, that could've been your problem.

Regardless of what width the wall was if you were trying to match an existing roof, your H.A.P cut should've matched the existing rafters

If your doing new work and for some reason you want to set the ridge, you have to know the exact ridge height to do so. Cutting the rafters which ever way you do them whether using a framing square or calculator is always done first regardless if you set the ridge first or after you lay out your rafter.

If you know how to figure out the exact ridge height and you set it first and then lay out your rafters(not measuring from the ridge and down) using a square or calculator and they don't fit, you either did something wrong with the framing square or calculator, or you set your ridge height wrong.

Can you explain more in detail of what happened?
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Joe, the guy who started framing this job simply used the preset marks on his speed square, you know, the diamond that marks 3-1/2" for the seatcut? Anyways, I didn't take notice of it until I went to lay the sheathing and saw that it didn't even TOUCH my rafters, as his were higher than mine. Anyways, I removed and re-cut the rafters to match mine and all was well. I discussed that issue with the HO, because he had issue with me taking some of the rafters off, and he disagreed with me. After somewhat of an argument, we both agreed that I was right demoing 4 rafters and recutting, than my 10. BTW, this was a two story Bay Window onto and larger than the original. The Ridge/Ledger board was arbitrarily nailed in place to the existing wall and the HO said "That looks like the right pitch!" Anyway..

The walls were all constructed from 2x6, and as I mentioned, the seats on the first rafters were cut for a 2x4 wall, based on the speedsquare used by the starting contractor. (I took over on this job for reasons I won't discuss here.)
 
#30 · (Edited)
DEAD_ONConst said:
Joe, the guy who started framing this job simply used the preset marks on his speed square, you know, the diamond that marks 3-1/2" for the seatcut? Anyways, I didn't take notice of it until I went to lay the sheathing and saw that it didn't even TOUCH my rafters, as his were higher than mine.
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You're loosing me here. It sounds like you came into a situation where part of a roof was framed with 4 rafters sitting on top of a 2x4 wall. Now you had to finish the roof using the same ridge height and rafter length, but your wall was a 2x6.

You cut your new rafters and nailed them up and never noticed a difference until you started sheathing.

If this is true, how come you didn't make a pattern and lay it next to the existing rafters the other guy cut and make sure they fit perfect at the birdsmouth and plumbcut at the ridge first before cutting and nailing the new rafters up?

Yiou have to do this no matter what when tying into an existing roof. You have to make sure the birdsmouth and H.A.P. cuts are exactly the same so that the top of your new rafter is exactly flush to the top of the existing rafter.

You have to make sure the length of the rafter is the same and the plumbcut is perfect with no gaps at the existing ridge when you lay it up against the existing rafter. You also have to make sure that your overhang is exactly the same as the existing rafter. I let the overhang run wild and then once I lay the new rafter up against the existing rafter, I scribe the existing overhang plumbcut and level cut onto my new rafter. Can't go wrong with a scribe.

If it was a bay shaped wall and the rafters were for a bay roof, you still have to cut a small pattern and lay it up against the existing birdsmouth and overhang to make sure you match the height and overhang. You also check the plumbcut at the existing ridge and make a pattern to fit to check the pitch.
 
Discussion starter · #31 ·
OK, The walls are 2x6!

The seats were cut 1-1/2 plumb and 3-1/2 level! "I" wasn't paying attention! I finished framing this roof, remember, it is a Bay window, so therefore has two hip rafters.

Now, in "MY" experience, knowing that I had 2x6 plates, I cut my rafters and hips with 1-1/2 x 5-1/2 birdmouths. I cut my sheathing and hauled it up the ladder and then found that the sheathing sat high/proud of "MY" rafters because "HIS" birdmouths were not cut as deep as MINE!

The pissing match between me and the HO was "I" screwed up, and therefore was in the wrong and the HO should not have to pay the extra labor to correct the situation. I fixed it anyway, NO CHARGE, and finished the job.

Mind you, I am 28' up, it is near or below 0* and with the windchill, blowing snow, and rain, IT was a SOAKING WET B!TCH! Not to mention, I was working of a 2x6 canitlevered scaffold, of sorts, nailed to the wall framing and climbing on ladders dug into ice/snow.
 
#32 ·
DEAD_ONConst said:
OK, The walls are 2x6!

The seats were cut 1-1/2 plumb and 3-1/2 level! "I" wasn't paying attention! I finished framing this roof, remember, it is a Bay window, so therefore has two hip rafters.

Now, in "MY" experience, knowing that I had 2x6 plates, I cut my rafters and hips with 1-1/2 x 5-1/2 birdmouths. I cut my sheathing and hauled it up the ladder and then found that the sheathing sat high/proud of "MY" rafters because "HIS" birdmouths were not cut as deep as MINE!

The pissing match between me and the HO was "I" screwed up, and therefore was in the wrong and the HO should not have to pay the extra labor to correct the situation. I fixed it anyway, NO CHARGE, and finished the job.

Mind you, I am 28' up, it is near or below 0* and with the windchill, blowing snow, and rain, IT was a SOAKING WET B!TCH! Not to mention, I was working of a 2x6 canitlevered scaffold, of sorts, nailed to the wall framing and climbing on ladders dug into ice/snow.
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We all make mistakes and that's all a part of learning. I know you said you were 28' up in the air with bad weather. Now you know the next time(if there is one) that you will go up 28' in the air in bad weather and check the existing roof FIRST so that you don't have to fix this problem 28' in the air.

Exposing the existing rafter at the plate and overhang is the most important part of tying into an existing house. I opened one up a bout 2 years ago where the existing rafters were 2x6's and the HAP cut was only 2 with a 5/12 pitch making the seatcut about 9-1/2". My rafters for the addition were 2x10's and the top of the rafters had to be flush with the top of the existing rafters.

I had to drop the addition walls down about 6-1/2" - 7". That was a big problem with headers and window heights.......etc.

The main thing is you found out solution and it was a good one and it worked and everyone is happy.
 
#34 · (Edited)
DEAD_ONConst said:
Do you cut your rafters BEFORE or AFTER you set the RIDGE?
Click to expand...
I calculate the ridge height, build temporary trestles, braced parallel to ridge, to carry the ridge perhaps a 1/4" lower than calculated. This way I can slightly lift the ridge board to match the rafters.

Then I cut the first two rafters calculated from plan and test them against the ridge. If all fits well, I start cutting the rest of the rafters and set another pair at the other end of the ridge. Then fill in the rest.

The ridge trestles also have a lower cross-member which holds scaffold planks for the guy setting and nailing the tops of the rafters.

By the way, this picture also shows my balloon framing technique, with let-in ledgers for the ceiling joists (which extend out to become soffit frame) and the upper beveled raftre ledger (which maintains my 18" insulation depth (R-67 ceiling). Rafters continue outward to meet joists at fascia.

These load-bearing walls are the inside of a modified Larsen Truss wall system that will have an outer cord of rough-sawn 2x3 (inner wall is r.s. 2x4), attached to studs with r.s. 1x4 gussetts 24" oc to create a 12" deep wall section for R-45 wall.
 

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#35 ·
Riversong said:
I calculate the ridge height, build temporary trestles, braced parallel to ridge, to carry the ridge perhaps a 1/4" lower than calculated. This way I can slightly lift the ridge board to match the rafters.

Then I cut the first two rafters calculated from plan and test them against the ridge. If all fits well, I start cutting the rest of the rafters and set another pair at the other end of the ridge. Then fill in the rest.

The ridge trestles also have a lower cross-member which holds scaffold planks for the guy setting and nailing the tops of the rafters.

By the way, this picture also shows my balloon framing technique, with let-in ledgers for the ceiling joists (which extend out to become soffit frame) and the upper beveled raftre ledger (which maintains my 18" insulation depth (R-67 ceiling). Rafters continue outward to meet joists at fascia.

These load-bearing walls are the inside of a modified Larsen Truss wall system that will have an outer cord of rough-sawn 2x3 (inner wall is r.s. 2x4), attached to studs with r.s. 1x4 gussetts 24" oc to create a 12" deep wall section for R-45 wall.
Click to expand...
I set ridges pretty much the same way you do. I really like the way you run the ceiling joists long. Got any more pictures?
 
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