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Construction Question

Started by Jeff, September 13, 2005, 05:58:20 PM

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J_T

We use to try our rafters on the outside  walls saved a lot of climing ???Then we would use one for a pattern and mark it and use it till the end . May not be clear I mean if it fitts at the footing it will fit the top if it is plumb and square 8)
Jim Holloway

Furby

Kirk, you can get all the definitions you want at Google.
Type:      define:Collar Ties             or what ever word you want.
Or we can have a nice long thread about it, and I do like this idea the best. ;)
The thing to remember is a lot of what you just asked has to do with "stick" framing.
It will differ a bit with the timber frame you have planned, and I can't even help you there.

Now if you want a hands on approach......I'll meet ya at Jeff's! How's that sound ???

Jeff

I could use, I mean Tammy can use the help. I am banned from pounding and lifting. Had my brother in law here today and we got another wall up. I measure and cut, he pounds and lifts.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

ScottAR

Birds mouth or Crows foot depending on who you ask is the notch where the rafter meets the top wall plate.  The wall plate is the horizontial boards at the top of a 2x stick built wall. 

Ridge board or ridge beam is the board that runs the length of the roof peak.  The rafters nail to it. 

A swayback roof usually has hips and dips along the peak.

Collar ties join a rafter to it's twin on the opposite side. 

I dunno about cross beams... 
Scott
"There is much that I need to do, even more that I want to do, and even less that I can do."
[Magicman]

Bibbyman

Looks like you're in pretty good hands there Jeff.

I've seen a number of carpenters lay out their rafters on the floor after they've studded up the outside walls.  Often they'd draw out the rafter and ridge pole with pencil and chalk line.  Then they'd make a pattern.  Then they'd cut a couple of rafters and "try fit" them over the pattern they've drawn.

When I was a young man I worked putting up hay for an old farmer.  He wasn't a professional carpenter but built his own home and barns, etc.  He knew I was on summer break from studying drafting in college so told me about how to read a carpenter's square and what all those numbers down the middle meant and how they could be used.  He said he was always called on to lay out gambrel roof barns in the area.  They would set him up in the shade with a pair of sawhorses and he'd mark out the parts and someone else would cut them.

When we were building onto our sawshed last weekend, Mary had picked up the square and asked how I was turning it to get the 5/12 pitch.  I showed her.  Later that day our son Chris stopped in to see what we were doing.  He picked up the square and said "Some day I'm going to figure out how to use this thing."  Mary jumps in and shows him what I'd shown her earlier in the day – except she was aligning up the 5" on the inside and the 12" on the outside of the square.  I saw what she was doing and corrected her.  She snapped "What difference does it make?. >:(  I said,  "One way's right and one way's wrong." ;D





Wood-Mizer LT40HDE25 Super 25hp 3ph with Command Control and Accuset.
Sawing since '94

logmason

That little book that comes with a rafter square shows proper layout.
The blade is the level cut, the tounge is the plumb cut. Pay attention to measuring line of rafter, this will show birds mouth depth. The calculations on the square will show rafter length per run. Don't forget to subtract half the thickness of ridge beam. Be sure to use the common scale and not the hip and valley scale.
The book that comes with a speed square shows it also, If you lost the book, buy another square , I have four  ;D

Furby

The fact is, most people have no clue how to use a framing square, and the ones most box stores carry don't come with any instructions and most don't have all the tools/rules printed or stamped on them.

SwampDonkey

There was an old gent in the neighborhood that built alot of structures, but one thing he made you understand was that he wasn't getting up on no roof he didn't build. He never trusted any one else's carpentry. :D :D :D :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

florida

Assuming your gables will face the 12 foot dimension the rafter should be 6' 8 1/2" measured along the top to the outside corner of the birdsmouth. In other words, cut your top pitch angle first then measure along the top  6' 81/2" and make a mark. Square down to the bottom of the rafter from that mark and that will give you the outside corner of the birdsmouth.
General contractor and carpenter for 50 years.
Retired now!

Larry

Are we gonna have to figure out how to cut stair risers on this thread?  I hope it's a walkout. :D :D ;D :D :D

Really cutting rafters is the next thing to rocket science on a complex roof.  After I figured out I didn't know what I was doing I bought a book called Roof Framing by Marshall Gross.  Just took a look and it has 474 pages on how to cut a rafter. ::)
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

mike_van

Larry, I had  that book or one like it, read the pages out of it.  I had to do a hip & 2 valleys to connect my addition to the main house, in the end, with all that knowledge, it still came down to just starting it,  checking measurments a few times & then just cutting a rafter.  If it's something you don't do all the time, like  roofs or stairs, boy, measure 3 or 4 times unless you want to make a lot of kindling wood.  The toughest thing I ever built was a bell tower for our grade school,  there were 4 square cuts [the ends of 4 rafters] in it, everything else was an angle or compound angle. The  hip roof was a real bear,
I had 3 western red ceder 10x10's - 30' long, light poles that got rotton at the ground. I resawed it all, built this tower
for the school.  Had some volunteers to help put it up, I was kinda proud when it all fit together that day. The roof is green metal.
I was the smartest 16 year old I ever knew.

D._Frederick

 Jeff,

"I could use, I mean Tammy can use the help. I am banned from pounding and lifting. Had my brother in law here today and we got another wall up. I measure and cut, he pounds and lifts".

How is that arm and shoulder coming along, when will you be able to use it more?


Minnesota_boy

Jeff,
One thing to remember, if you don't like the way the rafters fit the ridge beam, you own your won sawmill, you can make the peices any size you like to get the fit you want.  Nothing wrong with sawing a 2x7 if it looks better for your building.
I eat a high-fiber diet.  Lots of sawdust!

Jeff

Quote from: D._Frederick on September 14, 2005, 07:27:19 PM

How is that arm and shoulder coming along, when will you be able to use it more?


THey never got it fixed, in factthey are beginning to think I have some sort of "condition" that they aint figured out yet. My problems have progressed to both arms and elbows, and a leg. We dont know if they are related or not. THe leg is a nerve based problem, no feeling in my right foot and no reflexes. At times it extends up and into my hip. THis came on during phisical therapy for the shoulder.  THings keep getting worse and they dont knoiw why. I switched to a different dr to try to get some help.
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Kevin

When I build something like that I always like to lay it out on level ground first to get all my measurements.

dan-l-b

Hi Jeff long time no talk to.   :D

As far as laying things out we always try to draw it out on ou shed floor or blacktop drive using tapes and squares and stuff.  Usually get it close enough for "who its for" :D :D
I was down all winter with back problems.  5 MRI's couldn't give the docs enough evidence to justiy surgery.  I was in a tremendous amount of chronic pain and the docs were looking to see if I was working a disbility or WC angle.  It took a CT miligram before they could see the real damage and I was in surgery in 3 days.  That was April 1 st and thank God, I am back to work and all looks bright. 

Dan-l-b

Don P

I have no intention...or hope...of returning this body in mint condition. If I knew now what I knew then  :).

QuoteWe will be spanning the 16 foot direction.

I think I understand, crossbeams are collar ties...those are too high to be of much effect in resisting spreading forces when you have alot of snow on the roof.
I was thinking of double 2x8 purlins running parallell to the ridge about midway between the birdsmouth and ridge. supported in the gable ends under the rafters...beams running across the ceiling. These would help the double 2x8 ridge support the roof under heavy load (40 psf where you are I think?). If you wanted to cantilever a section over a small porch at the end extending those purlins, the doubled ridge, and cantilever beams off the walls would work up to about 4' out. Those beams should be very good stock. The rafters would then be doing light duty.



Main 12x16 building is brown. Double 2x8 ridge, cantilevers and purlins are red. 2x6 rafters are black. I figured each of the ridge boards at 1-3/4" thick. Plumb to plumb is 105-3/8". Is that anything close to what might work?

The right pic is the rafter layout showing what I mean by plumb to plumb. I stuck a square on it with square nuts at 6/12. In light gray is "stepping off" a foot of span at a step. Stepping works but is prone to cumulative error.

The diagonal measure of the triangle formed by the square and the board is in this case 1.118'. That is also known as the the line length ratio...go ahead multiply 94.25 (the horizontal run) x 1.118 (line length ratio)= plumb to plumb measure.

Jeff

Don, So, how are the purlans supported on the gable ends?  Are they installed under and after the rafters?
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Jeff

Don, How low would collar ties have to be in order to be effective?  My  wall hight is not a full 8 foot, it is only 88 inches. I want to get as much ceiling hight as possible
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Don P

The purlins could go after, I was thinking of bar clamping them up to a popped line across the undersides of the rafters, attach with a twisted hurricane strap, purlin to rafter, then clamp another 2x8 alongside covering the straps, then stitch the two 2x8s together. You could bevel/rip the tops to make it sit plumb and neat. Then go to the gable ends and put 2 studs under and 2 alongside and around the purlins, same with the ridge. Follow those load paths to the foundation.

Lower third of the triangle or below is usually considered good on collars, the lower the better.

Jeff

Isthere a way to estmate the ceiling hight using my width and pitch? 


What is a hurricane strap?  What is popped line? (chalk line?)
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Don P

Floor to UNDERSIDE of ridge is 132-1/4" (I put the ridge flush to the bottom of the plumb cut).  Thats a total rise of 51-1/2" above the wall top to TOP of ridge. (I assumed a 3-1/2" level seat cut on the bird,I also assumed 2x6 rafters at 5-1/2", ridge at 1-3/4x7-1/4" x 2 ply)

Hurricane tie...twisted metal simpson connector, about 4"x 1-1/2" twisted 90 degrees and punched full of holes...lets you hook things together at 90*. By code you need them at the birdsmouth to wall joint as well.

Popped line=chalk line...ever been smurfed when the line spills? :D

Jeff

Our codes dont call for hurricane straps.  Don, since I have a sawmill, couldnt I cut those purlins out of something solid and pretty, and leave them exposed acrossed the ceiling since they will be under the rafters? I can still insulate and put a ceiling on leaving the purlins exposed?
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

Furby

Actually Jeff, mine did on the addition, don't know about a shed.
They not only help against wind but also against seperation due to snow load on rafter framed roofs.

Jeff

Well, maybe they do, but I have seen a lot of garages and stuff go up around here and never seen them used. I'll find some
Just call me the midget doctor.
Forestry Forum Founder and Chief Cook and Bottle Washer.

Commercial circle sawmill sawyer in a past life for 25yrs.
Ezekiel 22:30

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