FAQs about how to use a framing square.

This article series explains how to make quick use of a framing square and its imprinted data to get some basic roof measurement data like roof pitch or slope, rafter lengths, and end cuts, stair stringer cuts, lengths of braces and other construction measurements.

Framing Square FAQs

These questions & answers about using each of the tables on a framing square were posted originally

at FRAMING SQUARE USER'S GUIDE - home . Be sure to see the details given there and in that article series.

at FRAMING SQUARE N JOISTS RAFTERS N RUN FT-IN - blade back<

Explanation of the "N-Joists" table on a Framing Square

Mod:

The numbers in the "N-Joists" table are based on 16" centers....i.e., 7 8-0 for an 8 ft. wall, end to end, 1 to start + 96" (8ft) /16" = 6, thus 7 studs required;

Try it for the other numbers:

40 52 0; 39 16" increments in 52 ft. + 1 starter = the 40 studs [or rafters]

Reading under the 4", 5", 6", 7", and 8" columns on the framing square blade back you'll see that data table continuing up to

40 52 0

On 16 inch centers the numbers provide end to end to count, i.e., 7 8-0 ....1 stud to start then 1 every 16"; 96"/16"=6 (+ the starter =7.

40 52 0 [1 to start + (52*12) / 16=39) 39 +1 = your stud or joist count if on 16" centers.

Youre Welcome. - On 2019-12-12 by Dennis Hagy -

Reply by (mod) -

Dennis,

Thank you so much for these notes.

Even the company that manufactures the squares and continues to include this table was not able to write an explanation of what the table is doing.

If you're someone who works in the field and wants to be identified and linked to you're welcome to do that just contact me using the page top or bottom CONTACT link and I can post that information

Followup by Dennis Hagy

Your welcome sir. I grew up with a carpenter step father who schooled me up on the tools of the trade. I hadn't used a framing square for several decades. As I prepared to cut some stair stringers I bought a new Empire framing square and used a search engine to find this information web page to do a self review.

As I reviewed the material the parts I had forgotten started coming back. I was surprised that the piece I commented on was a mystery. Glad to help. I'm just a hobby craftsman, but have a lot of fond memories of house builds with my step father. Thank you.

Reply by (mod) -

Thanks Dennis;

Indeed I first started pounding nails in 1947, helping my father build a dock along the Rapphannock in Virginia. And I've used framing squares for a lifetime, but this particular table, sported on Empire and other brand framing squares has eluded me. I wrote to Empire asking for help but the company - at least after nearly a year - has not responded except to say "we'll get back to you".

One can but wonder if the Empire framing square and level company, now in business for a century, has suffered by the death or retirement of anybody at the company who actually understands framing square use.

You can also contact Empire directly (maybe you'll have more luck than I did) at www.empirelevel.com/framing-squares.php 29 Empire Drive, PO Box 800, Mukwonago, WI 53149
800-558-0722 262-368-2127 Email: 29 Empire Drive, PO Box 800, Mukwonago, WI 53149 USA Tel: 800-558-0722 262-368-2127 Email: empire@empirelevel.com

I've asked the company for help a second time as of 2019/12/14 10:29 AM

The reply - to date is:

"Thank you for contacting Milwaukee Customer Experience Support Team! Your email has been received and you will receive a response within 48 hours. In the event you need immediate assistance, please reach us at 1-800-SAWDUST.

Our support business hours via phone are Monday-Friday, 7:00 a.m. to 6:30 p.m. CST.

Thank you for your business!"

from: CXHelp <cxhelp@milwaukeetool.com> via milwaukeetool.onmicrosoft.com

We'll see what happens.

[Note: as of January 5 2020 the response from Empire Level and Milwaukee Tool is shown between the following brackets: [ ]

Suggested rounding off approach on rafter lengths from the framing tables

Thanks for a great article; after 60 years as a home handyman, I finally started wondering about all those strange things etched into my framing square, and if they added the 10ths and 12ths scales just to separate us hobbyists from the pros.
And I really enjoy your method of presentation; Really? Yes, really!

I can make pretty good sense of your usage explanations, but I find some of your rounding-off habits very puzzling.

In the section on calculating rafter length, under "Allow for Ridge Board Thickness", for example, you come up with a length including overhang, of 259.56" and you say you'd round it down to 258"! I assume you meant you'd round down to 259", but that is still off by over 1/2" which sounds crazy to me. Heaven forbid someone ELSE finishes cutting rafters for you!

Then in "Final Adjustments", you subtract 3/4" for 1/2 the ridge beam from your overall (which I notice you calculated using the full 259.56", NOT rounded down to 258" or 259").

But if I subtract 3/4" from the run BEFORE calculating the rafter length, I come up with (12'-(.75"/12")) x 21.63, or 258.21" rather than 258.81", a difference of 5/8", which still seems to me like enough to cause trouble, even if you don't do the other rounding you mentioned. I would certainly be frustrated if I were doing the roof sheathing!

But thanks again for putting all this out there; it IS very helpful. On 2018-12-09 by Mark

On 2018-12-09 by (mod) -

Thank you so much, Mark, for your helpful critique. I will review the text to see if I can make it less confusing.

The reason that I round the way that you observed is that in calculating a total rafter length there is both a critical distance and a non-critical distance.

The critical distance is the length of the rafter that actually covers the building, that would be from the center of the ridge or the face of the Ridge board to the outer edge of the top of the exterior wall.

Past that distance is the extra length of the rafter to account for the eaves or soffit overhang.

In that case it's not at all critical whether the final distance or the projecion of the eaves is 25.59" or 24".

Therefore, the total rafter length, including the eaves projection, if it comes to an odd number, is going to get rounded up (longer) or down (shorter) to what I consider a sensible one.

Whun the framing square, rafter tale, or other calculation gives 259.59", I prefer to round the total rafter length up or down to an even number and if possible a number that wastes minimum material.

For example I wouldn't buy a 14 foot rafter if my ultimate length needed to be 145.59" or 12 foot 1.59"

In that case, because the distance is including the projection past the wall and including the eaves overhang, I would simply shorten the eaves overhang by 1.59 in and use a 12-foot rafter.

Watch out however. I would agree with you completely that when calculating the rafter length to the bird's mouth Notch for the wall top placement of the rafter, that needs to be quite accurate. There I would round to the nearest tenth of an inch.

I'm grateful that you took the time to write and I hope this explanation makes sense.

Tips for using the Octagon scale on a framing square

Oops. I got screwed up by the 1/10 vs 1/12 scale. 67' -> 13-10&1/2", 50' -> 10'4&1/2, 100' -> 20' 9".

Regarding the "what good is it" comment on the short length of the Octagon scale, you can easily scale it up to larger scales by letting each interval on the scale represent feet.

My Mayes 10440 lines its octagon scale up with the tongue, so it's largest mark on the 5 scale is the dot '67'. If you treat that mark as 67 inches, as in your text, then the half-side measurement would be 13-7/8". If you treat the '67' as 67 feet, then the mark corresponds with 13-7/8 feet, which you could transfer over to the 1/12 inch scale and read as about 13'-10&3/4".

Or, for a 50 foot wide octagonal pavilion, the half-side length would be 10'-3&1/2".

For octagon widths larger than 67', you could easily divide by two and then double the half side length.

For example, a 100' octagon has sides twice the length of a 50', so double the 50' octagon's half-side length of 10-3&1/2" to find a 20'-7" half-side length for the 100' wide octagon. Other multiples would work similarly - On 2018-03-06 by Dave X

Reply by (mod) -

THanks so much for the added comments and details, Dave. That will be helpful to other readers.

 

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Continue reading at FRAMING SQUARE TRUING PROCEDURE or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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FRAMING SQUARE USER'S GUIDE FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ROOFING

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