the string sags, doesn't it?

[zaktark]

I'm putting 5-foot high walls topped by roof rafters + collar ties on the second floor of my framed 24 X 30 building.

The eaves are big -- they extend out about 3 feet (or 2 feet, measuring horizontally), approx.

I've got one end and about four sets of rafters erected and braced.

It seems like the line of the ridge board, and the lines of the bottom ends of the rafters, at the eves, are the three lines that the eye will go to when this is done, and tell anybody whether the building looks wonky or not.

I want to put up three temporary boards at the other end of the building, and attach three strings from one end to the other, so I can know at a glance if one of my sets of rafters is "off" for whatever reason, and also as a check that the ridge line hasn't done something wierd.

Putting those strings there, tying each end to a protruding nail, no problem. But would I ever get them tight enough that they don't sag in the middle? I don't think so.

Is there a solution or another way of going about this?

Thanks in advance for your thoughts, opinions or advice.

Zaktark

[Tom R]

I wouldn't really think your string would sag over 30', - - but to check it run your stringline, - - then get at one end and 'sight' from the near end to the far end, - - and see if your center is 'in-line', - - if it is sagging, adjust it up as necessary, - - now you've cut your string distance in half.

[zaktark]

Tom -- I appreciate the reply. I guess there's a couple words or phrases I don't understand.

What's "your stringline". Is this the string I've tied between two nails 30 feet apart?

I sight down the string I've tied there, and if the centre is sagging, I make the string tighter, yes? -- is that what you mean by "adjust it up"?

But what I really don't get is, "now you've cut your string distance in half". Obviously I'm misunderstanding something, cause I don't see how the distance is cut in half.

As you can tell, what I know about this is zero. Thanks for your patience.

Zaktark

[Tom R]

No, - - that's alright, - - I'm probably just not making it clear enough, - - yes, - - 'sight' the string that you've stretched the 30', - - nothing is straighter than your eye (line of sight), - - now, - - taking for granted you're working alone, - - when you're 'eyeing' the near point to the far point of the line, - - estimate how low your center is, - - let's say it's about 1/8", - - move your ladder to the center now and partially drive a nail 1/8" above your stringline, - - now go back and sight both ends again, - - and see if your nail is 'in-line' with your ends, - - once you determine it's in-line, - - re-run your string from the beginning point, - - to the center-nail, - - pull tight, - - go once around the nail, - - then pull tight to your end-nail. Now your string distance is cut in half, - - because it has the center nail holding it also.

In other words, - - you're basically sighting 3 nails, - - you already know where your end ones go, - - so you're just getting the middle one in a line with them.

Let me know if you do or don't understand what I mean now. I don't mind questions at all.

[zaktark]

Great, Tom. Got it this time. So simple and obvious -- once somebody tells you how to do it. This is a big help, and now I understand completely what you're suggesting. Thanks for clearing up the problem. Z.