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How would I be able to install trusses on the building walls in which the tails were pre-cut to length, and have them come out perfectly straight to one another, without using a string line, mainly because of wind?

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    use a laser for alignment – jsotola Feb 26 '18 at 2:29
  • @ jsotola. That would probably work, but I don't care for the setup time. – user81998 Feb 26 '18 at 6:25
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I've rarely used a dryline to set trusses. Plumb and straighten your walls, then set each truss heel to the same wall. Be sure to not rotate truss direction from one to another. Because the truss plant's jig probably isn't perfectly symmetrical, this would result in humps in the roof plane.

If you can't straighten the walls, chalk a line on the top plate from which to set heel position. If wind is a factor, use an eye from one end and have an assistant (or two) pin the line in position at midpoints and snap each way.

  • A chalk line on top of the wall is the way to go and would not be affected by the wind. My tails will be as straight as the chalk line. Brilliant! – user81998 Feb 26 '18 at 16:20
  • What's the difference in a string line and a chalk line? A string with chalk on it? – Ed Beal Feb 27 '18 at 23:39
  • I use the term dryline for a plain line used as a temporary straight indicator, whereas a chalk line is a box with a reel inside it that holds chalk. – isherwood Feb 28 '18 at 2:18
  • @ Ed beal. A string line AKA a dryline is a tool used for layouts, specifically for checking if a structure is standing straight and even. It's usually made of strong material which enables it to be pulled tightly to avoid sagging. A chalk line just needs to be pulled tight long enough between gusts to mark a line on a surface. I hope this helps. – user81998 Feb 28 '18 at 2:36
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How do you make sure you have a perfect rectangle - corner to corner will always be equal - make your measurement the third angle of a triangle.

So for all intents and purposes your question asks how to do this with out a string line and your concern is because of the wind.

A perfect rectangle will have equal length from one corner to corner measurement (South-East to North-West) as it will from the other corner to corner (South-West to North-East ). Because basically it is two right triangles joined together.

So if you start at placement with your first truss - you make one measure on one side after that it is simple. See my example picture - black lines are trusses , orange lines are wall supports and the light blue is a measurement you make - whether you want to use a single pre-measured string or tape measure - you are not doing this by dragging a line across the roof .. and this is easy enough with a laser line as well (maybe easier).

You can place the first truss and measure where to put the second truss and cut a line at that point - or use the Pythagorean Equation A² + B² = C².

A² = Truss length. B² = center on center truss to truss. C² = my little blue lines distance corner to corner.

A laser will work fine and you will not have any huge setup time - this is easier than you think.

[If the math is too much use the scientific calculator on your computer.]

Trusses Measure for Parallel

Truss one Step 1 and 2 Truss Steps 3 and 4 Truss Step 5 Trusses not aligned properly

  • @ Ken. I'm lost with most of your answer. You said: "So if you start at placement with your first truss - you make one measure on one side after that it is simple." Make one measurement from where to where? You said: "orange lines are wall supports and the light blue is a measurement you make" What is a wall support? A measurement of what? You said: "You can place the first truss and measure where to put the second truss and cut a line at that point I have no idea what you mean by "cut a line. – user81998 Feb 26 '18 at 8:12
  • @JimWatson orange lines = the building walls. Place your first truss. You have a set distance truss to truss so measure that distance at only one end. By making sure your trusses are parallel in this manner - you are also making sure they align one to the other. If the truss is pushed one direction or the other your distance would be off and instead of being a rectangle you would have a parallelogram (looking from above) - the distances would not match. the first truss needs to be correct - after that all should be straight forward. I will edit my post with pictures. – Ken Feb 26 '18 at 8:49
  • @ Ken. Thank you for taking the time to answer my question, It would only work if the walls were perfectly square which is not likely considering that the walls would also have to be perfectly plumb. The slightest variation would throw off everything. aiso, the walls would have to be perfectly straight. Measuring diagonally is not very accurate to get the end result of having the ends of the tails in a straight line if you consider that to be off a tiny bit will be compounded when you measure the distance the tail projects from the outside edge of the wall. Thanks again! – user81998 Feb 26 '18 at 10:13
  • @Jimwatson You can measure from tail to tail however the fact that the walls are not square - your trusses would need to be in a parallelogram so to speak so you are correct your measurement would be off. In your scenario the only easy way I know of to do what you want to do is with a laser line or a string line. Maybe a jig setup but I think that would be way too much work. I know they make jigs for spacing but not sure on the pre-cut tail alignment. – Ken Feb 26 '18 at 10:50
  • @ Ken. Once again I'm befuddled by your answer. What does spacing, AKA as layout have to do with tail alignment? Remember, I said that the walls might not be perfectly straight and/or have waned edges on the top plates. What would a jig do better than I can by measuring how much a tail projects from the outside of the wall? Remember, I said that the walls might not be perfectly straight and/or have waned edges on the top plates. I can't use a stringline because as I said in my question I'm concerned about the wind. – user81998 Feb 26 '18 at 11:26

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