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.

2020/01/05 Matt said: @Mark in Ohio,

It may seem too obvious but it looks to me like it's simply a calculation to determine the run based on number of studs, joists or rafters on 16" centre.

eg. 17 joists (16 joist cavities) would simply be 16x16" = 256"/12" = 21' 4"

6 joists (5 joist cavities) would be 5x16" = 48"/12" = 6' 8"

Reply:

Thank you Matt, that's helpful. I'll keep it in the article. Your view is consitent with Denis Hagy's explanation below and can work for stud walls or roof rafters.

Your example and Dennis' explanationare now found at FRAMING SQUARE N JOISTS RAFTERS N RUN FT-IN - blade back<

On 2019-12-14 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: [ ]

On 2019-12-14 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.

On 2019-12-12 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

On 2019-12-12 by Dennis Hagy - explains the "N-Joists" table

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 2019-10-17 by (mod) -

I'm still looking at this Mark. Remarkably even some brand new framing squares from Empire include the "The Number of Joists, Studs, Rafters N Run Ft-In Table" - as I confirmed this week at a Home Depot store; yet the framing squares are sold without any guide to their tables and Empire - the manufacturer - has not replied to our inquiry.

On 2019-09-16 by (mod) - Table of Number of Joists, Studs, Rafters N Run Ft-In Table on the back of the framing square

I've been promised to reply from the manufacturer but so far they haven't said a thing other than will get back to you. I'm still researching this topic.

On 2019-09-10 by Mark in Ohio

Thank you danjoefriedman :)

On 2019-09-10 by (mod) -

Mark,

So sorry, ill get to work on that added info. (I think its aldo in some of our references)

On 2019-09-10 by Mark in Ohio

The one reason I was reading your page was to find out how to use the "The Number of Joists, Studs, Rafters N Run Ft-In Table" on the back of the square. Unfortunately your data just says [Text in process].

On 2018-12-09 by (mod) - suggested rounding off approach on rafter lengths from the framing tables

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.

On 2018-12-09 by Mark

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 2018-03-16 by (mod) -

Buck

at HOW to PRINT InspectAPedia.com WEB PAGES - inspectapedia.com/Admin/How_to_Print_Web_Pages.php
we have suggestions on easy ways to print hard copies of InspectApedia pages or articles.

You can do that for free.

On 2018-03-15 by Buck

How can I get a paper copy of article with illustrations. Monitor is hard on eyes. Thanks

On 2018-03-07 by (mod) -

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

On 2018-03-06 by Dave X

@Dave X,

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 2017-10-13 by Jeff M.

The Number of Joists, Studs, Rafters N Run Ft-In Table on a Framing Square Blade Back

Does any one know how this area on framing square works

On 2017-08-15 by RogerBethune

How to utilize square for side cut of hip & Jack rafters, assuming, on hip @ 45 degree, angle @ top ,square on 12/12 , then plumb side cut, are different pitches, not on 12/12 @ top mark for plumb lines, ects?

On 2016-11-08 by (mod) -

Casey: I'm not sure which "that" you're asking about.

But generally, the rafter length can be measured along the top or bottom of the rafter as long as both rafter ends are cut plumb.
However the true rafter "run" length is the unsupported length between the ridge and the beginning of the point of bearing on the top plate. That would be a shorter distance than when we include the top plate and shorter than when we include the rafter tail that extends out past the house wall to form the roof overhang.

On 2016-11-08 by Casey

Is that the distance from the two farthest points?

Reader Question: What does the number 27 have to do with a framing square?

2016/04/23 Jim said:

What dose the number 27 have to do with a framing square

Reply: nothing

Jim,

Somehow I smell a trick question from someone's homework or from a carpentry quiz. Arm-waving aside, I don't know. I've looked through our framing square articles, books, and on the framing square itself to look for something special about 27 and framing squares - to no avail.

While 27 feet is used as a rafter length in some texts to calculate run length, and while 27 appears ALMOST as a whole number in some framing square tables, that's about it.

Perhaps if you can give me some details about the origin of your question I can have better success.

At the end of this article atReferences or Citations you'll find more texts and articles on using a framing square and written by other experts.

...

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

Or see these

Building & Roof Measurement Articles

• 6-8-10 RULE to SQUARE UP ANY STRUCTURE
• ANGLE FINDER LEVEL
• ARCTANGENT CALCULATES ROOF / STAIR ANGLE
• CALCULATE RISE & RUN from SLOPE
• DECK LEVEL PLUMB SQUARE-UP 6-8-10 RULE
• FOLDING RULER ROOF SLOPE CALIBRATION
• FRAMING SQUARE USER'S GUIDE
  • FRAMING SQUARE PARTS DEFINED
  • FRAMING SQUARE TABLES LIST
  • FRAMING SQUARE RAFTER LENGTHS
  • FRAMING SQUARE for BIRDS MOUTH CUT
  • FRAMING SQUARE OCTAGON TABLE
  • FRAMING SQUARE BACK TABLES
  • FRAMING SQUARE BRACE TABLE
  • FRAMING SQUARE N JOISTS RAFTERS N RUN FT-IN
  • FRAMING SQUARE ESSEX BOARD MEASURE
  • FRAMING SQUARE DIVISION WARNINGS
  • FRAMING SQUARE COLOR & MATERIALS
  • FRAMING SQUARE DETERMINES ROOF SLOPE
  • FRAMING SQUARE for STAIR BUILDING
  • FRAMING SQUARE-UP 6-8-10 RULE
  • FRAMING SQUARE TRUING PROCEDURE
  • FRAMING SQUARE HOW-TO MANUALS
• FRAMING TRIANGLES & CALCULATIONS
• FROGS HEAD SLOPE MEASUREMENT
• HOPPUS MEASURER
• ROOF FRAMING TIES & BEAMS
• ROOF MEASUREMENTS
• ROOF SLOPE CALCULATIONS
• ROOF SLOPE TABLE, TYPES, WALKABILITY
• STAIR RISE & RUN CALCULATIONS

Suggested citation for this web page

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

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to BUILDING ROOFING

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Citations & References

In addition to any citations in the article above, a full list is available on request.

---

ADVERTISEMENT

---