Bird's mouth cuts - necessary?

[winston1]

That is a form of a gable roof. You will need ceiling joists to keep walls from pushing out or trusses. If it is not an optical illusion I believe the plate height on the front wall is higher than the plate wall on the rear wall. If the span is not to great your joists could go level from front plate height to back rafters. I still would cut birdmouths. How wide and deep is your building going to be? I would guess that picture to be somewhere from 4/12 to 5/12 pitch.

 

[carpenter383]

That is a form of a gable roof. You will need ceiling joists to keep walls from pushing out or trusses. If it is not an optical illusion I believe the plate height on the front wall is higher than the plate wall on the rear wall. If the span is not to great your joists could go level from front plate height to back rafters. I still would cut birdmouths. How wide and deep is your building going to be? I would guess that picture to be somewhere from 4/12 to 5/12 pitch.

You're right that ceiling joists would be the strongest way to hold the walls togeather, but it's not a must. If he uses a strong ridge pole with cripples to support the ends of the ridge pole (puts the load on the walls), it should be fine. Also a good anchor from rafter to ridge pole is important.

 

[winston1]

You're right that ceiling joists would be the strongest way to hold the walls togeather, but it's not a must. If he uses a strong ridge pole with cripples to support the ends of the ridge pole (puts the load on the walls), it should be fine. Also a good anchor from rafter to ridge pole is important.

I agree, your right, could be done that way.

 

[/pine]

I agree you should make a quick study of the use of a framing square...be aware not all squares are the same...some have random (garbage) information rather than useful rafter tables etc....

you need to learn how a rafter is measured before you can make any seat cuts the "birdsmouth" is actually the point the seat cut makes and one of the main reasons to make them is to help keep the framework square and true...

Be sure to pick a slightly crowned board to cut your rafter pattern since most of the boards will have some crown...by using a pattern to mark all the top and seat cuts...you can use the "birdsmouth" to keep the wall straight with the ridge (birdsmouth is the exact outside edge of (wall) frame)

If you are using only 2x4 for reafters the adjacent ceiling joist or ties makes the "seat" aas there is no meat to cut one...usually a wedge is added...

 

[two_bit_score]

I want to build a woodshed that looks pretty much like a run-in shed. Some plans I've seen call for a salt box style roof using bird's mouth cuts on the rafters. Can I eliminate those cuts and use rafter ties instead?

Check Simpson's Simpson Strong-Tie - Helping to Build Stronger, Safer Structures


If it's a code compliant connector they have them.

 

[herd]

One of the reasons for the bird's mouth is so that you have more of the rafter sitting level on the top plate. Bevelling the top plate/header/load beam or whatever the rafter sits on will work esp if you run celilng joists and but up to the rafter and hard nail.

I personally would not build w/o the bird's mouth, whether gable, shed, or hip roof. The more you can adequately/accurately fasten the parts, the stronger the entire unit will be.

If you do the bird's mouth, don't cut any deeper than 1/3 of the rafter's width, it will weaken the board. I always do one inch depth, sometimes 1/2'' on largers rafters.

 

[ElDorado]

I have had great luck with rafters/birds mouths with a Swanson speed square. Included with the speed square is a little book that makes birds mouth cutting a snap. Good luck.

 

[bjr]

In my part of the world the county building inspector runs the county and he doesn't even look at a print unless he sees a state certified engineers stamp on it. The neighbors tried to get away with out a permit and their efforts are now setting in a rubble pile waiting to be hauled off. It don't matter what you want to drive a nail into I can't happen unless the inspector says it's okay. bjr

 

[brin]

In my part of the world the county building inspector runs the county and he doesn't even look at a print unless he sees a state certified engineers stamp on it. The neighbors tried to get away with out a permit and their efforts are now setting in a rubble pile waiting to be hauled off. It don't matter what you want to drive a nail into I can't happen unless the inspector says it's okay. bjr

So based on this we are all just renters ! even if we have our farms paid for we are only tenants as long as you can not do what you want to with your property especially in a rural area and on top of that we pay our rent in the form of every increasing taxes.

 

[2manyrocks]

About 20 years ago, a friend sent me an article from the newspaper in Seattle that tried to explain how much extra a building lot cost because of all the regulations. At the time, it was several thousand dollars. No telling how much now.

I've sort of been curious what the concern is about making the bird's mouth cut. Once you get the hang of it, it's not difficult. Structurally, the metal plate connectors are much more resistant to pullout and uplift.