No Birdsmouth????????

Started by peter nap, October 06, 2007, 02:37:10 AM

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peter nap

October 06, 2007, 02:37:10 AM Last Edit: October 06, 2007, 02:41:37 AM by peter_nap
I'm using a fairly small rafter (2X6) and a shallow pitch )3-12)

Unless the birdsmouth is perfect (and mine rarely are) I always thought that it weakened the roof at that point.

I was thinking about cutting the plate on a 14.5 degree angle (3-12) and forging some 2" brackets from 1/4" stock to set the rafter in rather than cut birdsmouths.

Seems like a stronger connection,

Any thoughts?

desdawg

#1
October 06, 2007, 08:33:23 AM
The notch you cut is filled by the double top plate and provides a place for two horizontal surfaces to meet. The angle cut would create a tendancy to slide downhill. I would think using H-25's at the connection would be simpler and more effective.
I have done so much with so little for so long that today I can do almost anything with absolutely nothing.

glenn kangiser

#2
October 06, 2007, 09:48:05 AM
I think a little practice cutting the birdsmouth would be the cheapest and easiest to do.  It would be approved structurally where the brackets would need official approval if inspected.  It has been brought out that it should only go 1/3 of the way into the board and the amount left would still be sufficient for any load on the overhang.  To avoid weakening it don't overcut the birdsmouth with a circular saw.  Finish with a hand saw or reciprocating saw to avoid overcutting.

As desdawg pointed out the cut you proposed would tend to slip, weaken the top plate and likely over time could try to stretch the fastener holes and slide down hill.
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

PEG688

#3
October 06, 2007, 09:57:31 AM
Quote

 #1: a) Unless the birdsmouth is perfect

        b)   (and mine rarely are) I always thought that it weakened the roof at that point.

  #2: I was thinking about cutting the plate on a 14.5 degree angle (3-12) and forging some 2" brackets from 1/4" stock to set the rafter in rather than cut birdsmouths.

  #3: Seems like a stronger connection,

  #4: Any thoughts?

   

 #1: a) Few things are  ever "perfect".


     b) Why is that? Poor quality saw ? , dull blade, .

    Bad birds mouths would be better than a sloped top plate.

Lets work on getting those cuts looking better. By answering question  # 1: b, then we can move on.

 #2: Simpson will sell some "widget" cheaper and MTL better suited for that job , BUT birds mouths are not that hard with proper tooling and some patience.

 #3:   I agree with the "dawg"  ;D I'd recomned a H1 instead of H 2.5's in most cases though.

 #4:   You asked  ;D

 G/L PEG

When in doubt , build it stout with something you know about .

PEG688

#4
October 06, 2007, 09:58:24 AM
QuoteI think a little practice cutting the birdsmouth would be the cheapest and easiest to do.  It would be approved structurally where the brackets would need official approval if inspected.  It has been brought out that it should only go 1/3 of the way into the board and the amount left would still be sufficient for any load on the overhang.  To avoid weakening it don't overcut the birdsmouth with a circular saw.  Finish with a hand saw or reciprocating saw to avoid overcutting.

As desdawg pointed out the cut you proposed would tend to slip, weaken the top plate and likely over time could try to stretch the fastener holes and slide down hill.


Oh come on , no one , two , three etc outline , no wonder you beat me  ;D
When in doubt , build it stout with something you know about .

glenn kangiser

#5
October 06, 2007, 10:02:55 AM
How did I do PEG?   Being primarily a steel guy, I of course have to bow to you. ::)
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.

peter_nap

#6
October 06, 2007, 03:13:19 PM Last Edit: October 06, 2007, 03:34:44 PM by peter_nap
Like you said PEG,,,,I asked.

No I have a number of top quality saws and sharpen and set them myself (One of the advantages to being a knife maker)

They are one of those things I hate to do and I guess that's why I don't do them well.

Buying brackets is not nearly as enjoyable as making a swage block to stick in the hardie hole and spending a day at the forge!

Majority and experience rule though! Thanks ;)

Didn't get any work done today anyway. I bought a new rifle last night and spent the day working up loads for it.

firefox

#7
October 06, 2007, 10:29:45 PM Last Edit: October 06, 2007, 10:31:24 PM by firefox
Hi All,
   In case you are interested the Simpson widget is a VPA.
Bruce

MountainDon

#8
October 08, 2007, 08:54:52 PM
Been a way a few days.... I must make a belated comment on the birdsmouth question.

As pointed out the sloped top plate will not transfer the downward vector from the rafter to the wall as well as a horizontal will.

In my experience, such as it is, the hardest part of cutting rafters is getting over the mental block. It seems complicated, what with the somewhat esoteric chart on the framing square. But it's not too bad especially if you go into it with the mindset that at worst you'll have to re-cut a second pair as a trial, and that the first try can be used for something else. And it feels good once you've made it work!  :)
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