Maybe I'm in over my head..

[Tommy & Megan Price]

Trying to finish up on my kid's playhouse. Putting an A frame roof on it. How do I come up with the measurements for the lengths to cut the trusses?

8' X 8' box.

[js]

length calculator.

[Tommy & Megan Price]

/\45 / \ / \ > How do I come up with the measurements for the lengths to cut the trusses?

[skeezics]

framing square. set stops at the pitch you want to use and layout half of the distance from one side of the playhouse to the other. if the play house is 8 feet then your ridge is in the middle which would be 4 feet. if you use the layout 5 times you will have 1 foot extra for overhang. the overhange wil be 6 inches on a 12 12 pitch. this is realy hard to explain for me. much easier than doing it. sorry. maybe someone here can put it into words better than i. skeez

[Secret Squirrel]

"Tommy & Megan Price" wrote in news:eDzcc.2236 $ [e-mail]:

If those are to be 45 deg angles as you've indicated, then it is a simple right triangle and you can use old pythagorus' theorem x^2 + y^2 = z^2 and to simplify it further you've drawn a perfect 345 triangle. The base will be 4 (half the width of the box) the rise will be 3 and the hypotenuse (your rafter) will be 5 ft. You'll probably want to leave a little more for overhang of course.

[Frank Ketchum]

I would put the ridge in place first by temp supports on the ends and then measure it exactly. Be sure to leave some extra for overhangs!

Frank

[Doug Miller]

[snip]

It's a simple right triangle, and he can use the Pythagorean Theorem, whether those angles are 45 degrees or not.

No, he hasn't. He specified 45-degree angles. In a 45-degree right triangle, both of the short legs are the same size. Conversely, in a 3-4-5 right triangle, the acute angles are approximately 37 and 53 degrees, not 45.

Wrong. If the angles are 45 degrees, then the rise is precisely equal to half the width of the box, or 4 feet, not 3 as you stated. And the rafter length is

4 * sqrt(2) = 4 * 1.414 or about 5 feet 7 7/8 inches, not 5 feet.

Note to the original poster: this does not allow for *any* overhang of the rafters beyond the walls. Allow approximately 1.5 inches of rafter length for every inch that you want the rafter to project from the wall (when measured horizontally). [If you want to be precise, allow 1.414 inches. 1 7/16 is pretty close to that. 1 1/2 is close enough.]

-- Regards, Doug Miller (alphageek-at-milmac-dot-com)

For a copy of my TrollFilter for NewsProxy/Nfilter, send email to autoresponder at filterinfo-at-milmac-dot-com

[Bob S.]

jezzzzus Doug...wish you'd be a little more precise in your answers so we wouldn't have to guess at things....;)

Bob S.

[J. Clarke]

Draw the whole thing up to scale using an architect's scale (one of those three-cornered ruler thingies you get at Staples for about 4 bucks--they come two ways, "architect's" and "engineer's"--the "architect's" is made for fractional inch measurements, the "engineer's" for decimal--for construction you want an "architect's") and then measure off the drawing. If you don't have a drafting set already they have a nice basic one for 30 bucks that will with the addition of a drawing board (piece of MDF of an appropriate size will be fine) and a T-square (if you've not seen one there's a picture on the Staples site that says it better than I can) get you set up to draw just about anything you're likely to want to build.

The high-tech version--download the 30 day demo of Intellicad or Ashlar-Vellum or whatever CAD program you like and draw it up then take off the dimensions.

[Secret Squirrel]

[e-mail] (Doug Miller) wrote in news:XAAcc.20165$ [e-mail]:

You're right of course. I was still half asleep this AM when I posted this.

[Jay]

Buy a Johnsons Speed Square and the little blue book.

[TeamCasa]

Best advise yet.

Dave

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[Nate B]

"Tommy & Megan Price"

As you nicely see here in this thread, the average person can't do high school math.

Fortunately, building a roof doesn't actually require such math.

Go thumb through any "How to build a shed" book at Home Depot, the library, whatever. and see how to actually build a small roof. You clearly don't know how, and are heading in the wrong direction.

- Nate

[Luigi Zanasi]

On Tue, 06 Apr 2004 15:00:09 GMT, "js" scribbled:

Alternatively, you could draw half the roof on a sheet of plywood & take off your measurements and angles from that.

Luigi Replace "nonet" with "yukonomics" for real email address

[J T]

Tue, Apr 6, 2004, 3:01pm (EDT+4) [e-mail] (Tommy=A0&=A0Megan=A0Price) mumbles: =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0/\45 =A0=A0=A0=A0=A0=A0=A0=A0/=A0=A0=A0\ =A0=A0=A0=A0/ =A0 =A0 =A0 \ =A0 =A0 =A0 =A0 =A0 =A0 =A0

[Tim Douglass]

And this method works even if your walls aren't parallel, plumb or the same height.

Tim Douglass

[Danny Boy]

At least sqrt(2) times the 4' half-base length. Add for overhang. With 45 at both ends of the base, you'll have 90 at the peak.

Dan.

[Joe Willmann]

It is too late now but here is a secret that will prevent these kinds of problem in the future.

Make your first set of rafters before you put up the walls. After all the floor will/should be the exact same size as the walls. This makes it a lot easier. You build the floor. Draw a centerline where you want the ridge line. Then lay 2x4s on their sides at the correct pitch you want but on their side. Then mark. Then cut. You can also go ahead and cut notches for the top plates. And if you want you can then build trusses using the floor. Set them to the side and when the wals are up the roof goes much faster.