InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
How to use a framing square and its etched-on tables to figure out roof slope & rafter lengths, rafter cuts, brace lengths & cuts, stair stringer layout & cuts and other construction & framing layouts & saw cuts.
A carpenter's framing square includes some tables stamped right into the tool itself. This article 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.
Roof measurement methods: these articles explain various methods for measuring all roof data: roof slope or pitch, rise, run, area, and other features. This article series gives clear examples just about every possible way to figure out any or all roof dimensions and measurements expressing the roof area, width, length, slope, rise, run, and unit rise in inches per foot.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
Definitions of Parts of the Framing Square
[Click to enlarge any image]
The standard two-foot framing square is an L-shaped tool that is used to mark angles for cuts used in building framing, particularly roof rafters, stair stringers, and many other cuts or angles other than 90°.
On both the long and short arms of the framing square are marked various framing tables giving rafter lengths, roof slopes and the proper angle of cuts for various roofing connections such as a rafter end abutting the ridbe board, the birds' mouth cut at the rafter segment that rests atop a wall plate, hip and valley rafter cuts and other information.
Other tables include conversions of inches of rise/run to slope in degrees, conversion of fractions of an inch (1/32, 1/16, 1/8 etc. ) to decimal fractions, conversion of inches to decimal fractions of a foot, numbers of joists, studs, rafters, and even pilot hole size recommendations for wood screws.
Definition of the Parts of a Framing Square: blade, tongue, heel, front, back
The parts and faces of the framing square labelled in the framing square photograph above, and are referred to as follows:
The framing square blade or body: this is the wider and longer arm of the "L", normally 2" in width and 24" long.
The framing square tongue: this is the shorter and more narrow arm of the "L", normally 1 1/2 " in width and 16" long.
The framing square heel: is the point where the two arms of the framing square meet. In our framing square photo above the framing square heel is indicated by the yellow arrow. Below we take a closer look at the heel face and the back of the heel of the framing square.
The framing square face or front is the side of the square you will see if you look at the square while holding its longer arm, the tongue, horizontally with the shorter arm, the tongue to your right and pointing down.
When held in this position, the wider longer blade or body arm is pointing to my left and shows me a table of common rafter lengths per foot of tun, hip or valley rafter lengths per foot run. Below our photo shows the front or face view of a framing square.
On the face of the framing square blade you'll find rafter framing tables.
Below our photo shows the front or face side of the heel of a framing square. You'll see that the manufacturer's name (Empire) and the framing square model number (e1190) appear on the framing square's heel face.
We will discuss the inch-divisions shown on the heel face of the framing square in just a bit further along in this article.
The framing square back is the side of the framing square that you will see if you look at the square while holding its longer arm, the tongue horizontally with the shorter arm, the tongue, to your left and pointing down, as Fala is demonstrating in the framing square back photo below.
When held in this position the wider longer blade or body arm is pointing to my right, showing at least three different tables
List of the Various Tables Found on a Framing Square
Here we'll list all of the tables found on a decent quality framing square, then we'll explain how each of them is used.
Tables Found on the Front of a Framing Square Blade
Seen from the top edge of the framing square blade then moving downwards, on the front of the blade when you hold the framing square with the tongue or shorter arm to your right and pointing down you'll see inches marked in 16ths on the blade top edge, then the tables we give below, and finally inches marked in 8ths on the bottom edge of the blade.
Common Rafter Length per Foot of Run - this is the top line in the rafter length tables
Hip or Valley Rafter Length per Foot of Run
Diff in Length of Jacks 16 Inch Centers
DIff in length of Jacks 24 Inch Centers
Side Cut Length of Jack Rafters
Side Cut of Hip Rafter or Valley Rafter
Table Found on the Front of a Framing Square Tongue
When you hold the framing square with the tongue or shorter arm to your right and pointing down, on the outer edge of the framing square tongue are inches marked in 8ths, then the table I cite below, and finally inches marked in 16ths on the inner edge of the tongue.
The Octagon Scale in multiples of 5 (located in the middle of the tongue)
Tables Found on the Back of a Framing Square Blade
Number of Joists, Studs, or Rafters N Run Ft-In
Convert inches to decimal fractions of a foot
Change inches of rise per foot into degrees of slope
Wood screw pilot hole size recommendations
Conversion table of common measurement rule fractions in 32nds, 16ths, & 8ths into decimal fractions
[Older Framing Squares]: on older steel framing squares the back of the blade contained the Essex Board Measure, a table that allowed the user to estimate the number of board feet in a quantity of lumber of given dimensions, where one board foot is defined as a piece of lumber that is 1" thick x 12" wide x 12" long.
See HOPPUS MEASURER for the history of board feet.
Tables Found on the Back of a Framing Square Tongue
Tongue back: Brace Triangle Table, also referred to as the Diagonal Table or the Brace Rule
Details of Use of Each Table on the Face of a Framing Square
Rafter Length Tables on the Front of the Framing Square Blade
[Click to enlarge any image]
Our sketch above illustrates the concepts of run (horizontal distance) and rise (vertical distance) along the length of a rafter. Normally roof slopes are expressed as inches of rise per foot of run.
To use the rafter length tables on the framing square blade front you need first to understand the type of rafter you are cutting. For a common rafter, or for each of the other rafter types, these tables give the length of the rafter per foot of horizontal run.
Above we see the key to the lines in the rafter length table.
This key is at the left end of the front of the framing square blade. Below the number 18 we see a column of numbers.
Each number gives the length of a rafter type for a particular roof slope rise expressed as inches of rise per foot of run. In the photo above, under the inch number 18 (read as 18" of rise per foot of horizontal run) we see 21.63.
That tells us that for a common rafter on an 18/12 sloped roof, the rafter length will be 21.63" per horizontal foot of run.
Let's look at a 6/12 roof for some rafter lengths
Above my pencil is pointing to the 6-inch mark. Using the rafter length table below, this significes that we are looking at rafter lengths for the various types of rafters on a 6/12 slope roof.
A common rafter will be 13.42" long per foot of horizontal run on a 6/12 slope roof.
A hip or valley rafter will be 18" long per foot of horizontal run on a 6/12 slope roof.
The difference in length of sequential jack rafters spaced 16" o.c. will be 17.88" long on a 6/12 slope roof.
The difference in length of sequential jack rafters if spaced 24" o.c. will be 26.81" long on a 6/12 slope roof.
The side cut length of jack rafters will be 10.75" on a 6/12 slope roof.
The side cut length of hip or valley rafters will be 11.32" long on a 6/12 slope roof.
Finally let's look at a common rafter length for a very low slope roof
Here is another example of common rafter length for a very low slope roof. In the top line of the rafter table shown above near the heel of a framing square, look under the 3-inch mark where you find the 3" on the top edge of the framing square blade.
There in the top of the column of numbers you'll see 12.37. This tells us that the length of a common rafter for 12" of run will be 12.37" long if the roof rise is 3" in 12.
Octagon Scale on the Front of the Framing Square Tongue - multiples of 5 on the octagon scale
The octagon scale on the front of the tongue of some framing squares (including the Empire Level framing square illustrated here) is used to lay out an eight sided shape or figure. You will recognize this scale, if it's on your framing square, by noticing that it counts up in multiples of 5 with dots between the octagon scale markings.
Our photo below shows the unit-5 octagon scale on an Empire Level framing square.
Both entire homes and more-often towers or turrets are sometimes framed in an octagon shape while other structures use octoganally-shaped timbers and beams that were cut out of square stock. Interestingly Empire's own "Rafter Book" is silent on using the octagon scale. We did find an explanation of using the octagon scale at free-ed.net from which we excerpt and paraphrase below. See REFERENCES for the full citation.
To use the octagon scale to lay out an octagon we start working from a rectangle whose equal sides are of length L.
Measure to the center of each side of the rectangle and place a center-mark there.
[Click to enlarge any image]
Draw a straight line through each pair of opposing center marks on your rectangle so that you have a cross dividing the large retangle into four smaller squares.
To use the octagon scale on the framing square to cut stock into an octagon, use a pair of dividers whose ends are set apart a distance equal to the number of dots on the octagon scale that corresponds to the original length of the side of your starting rectangle. One leg of the dividers is placed on the starting line on the octagon scale and the other leg of the dividers is placed on the nth dot that corresponds to the original rectangle side length.
The dividers are then used to lay out their spread distance on each side of the rectangle to give the cut points or marking points of an octagon as follow:
Place one point of the dividers on the end of the center line at the edge of the rectangle.
The other point of the dividers will mark the first octagon cut line.
Repeat this process for each of the other ends of the center lines of the rectangle to mark all of the other cut points of the octagon on the end of your timber or stock.
Repeat this entire process, steps 1-4 above, on the other end of the square stock
Draw lines along the sides of your square stock connecting the corresponding octagon cut marks that you made on the stock ends.
Because the octagon scale on the framing square does not extend past 16" (the length of the gongue), what good is it? It's used to mark the cut lines on square stock that you want to trim into an octagonal shape. Examples of octagonal stock appear as decorative posts and beams.
Details About Tables on the Back of a Framing Square
The Number of Joists, Studs, Rafters N Run Ft-In Table on a Framing Square Blade Back
[Text in process]
Convert Inches to Decimal Fractions of a Foot
This framing square table converts inch measurements into decimal fractions of a foot.
1/2" = .04 ft.
6" = .50 ft.
12" = 1.0 ft.
Change of Inches of Rise per Foot into Degrees of Slope on a Framing Square Blade Back
This table provided on the back of the framing square blade helps you convert inches of rise to slope expressed in degrees.
6" of rise per foot of run = 26.50 degrees of slope
10" of rise per foot of run = 40 degrees ofslope
18" of rise per foot of run = 56.25 degrees of slope
24" of rise per foot of run = 63.50 degrees of slope
Convert Inch Fractions (32nds, 16ths, 8ths, 4ths) to Decimal Fractions
The table below, found near the end of the back of our framing square blade converts all of the common inch-fractions into decimal fractions.
1/32" = 0.31"
1/16" = 0.62"
5/8" = 0.625"
Table of Wood Screw Pilot Hole Sizes on the Framing Square Blade Back
Making use of the last bit of free space on the back of the framing square blade, Empire includes a table of recommended pilot hole diameter for wood screws of various sizes.
For example, in the table shown above, if you are using a #10 wood screw the pilot hole should be 0.109"
The Brace Triangle Table on a Framing Square Tongue-Back - The Diagonal Scale
On the back of the framing square tongue you'll find a brace measuring table giving the lengths of common braces in sets of three numbers, two equal numbers and a third fractional number stamped to the right of the equal number pair.
For example, looking at the back of the tongue of your framing square find at the triplet 33 33 46.67. The "67" appears as a superscript in a smaller character size to the right of the "46".
This scale is used for knee bracing or for post bracing in timber framing, and is also referred to as the Diagonal Scale on the Framing Square because the scale is telling us the length of the diagonal of a right triangle whose short arms are of equal length, for example 33" in the example I give below.
This brace measurement number triplet tells us that for a 33" brace the hypotenuse of that trianglular member will be 46.67" long on its outer or longer side. Now I know that no carpenter has a tape that measures in hundredths of inches. A rough carpenter will round these decimal fractions off to something she can understand.
The framing square engineers considered this problem and gave us a pretty good solution - the Conversion Table of Inch Fractions in 32nds, 16ths, & 8ths into Decimal Frctions on a Framing Square Blade Back discussed next.
Decimal Fraction to Inches Conversion Table
We listed this inch fraction to decimal fraction conversion table earlier in this article.
A savvy carpenter will use the table given on the right end of the back side of the framing square body to find common (close enough) conversions of fractions of an inch to 8ths, 16ths, or 32ds. That table is shown just below.
Let's use the decimal to inch conversion table above to find the length of our brace hypotenuse in the 33 33 46.67 example given above.
We want to convert 46.67" to something in eights or sixteenths of an inch. Look into the table and find the decimal fraction closest to .67.
I see that the entry for 5/8" = .625" and the next bigger entry is for 11/16" = .687". Without a lot of thought I think figure that .687 is the closest number to my target of .67" so I'll measure my cut to 46 11/16". Let's see just how close this table gets us to spot-on by calculating the numbers instead of using the table above.
Whip out your cellphone, turn on its calculator and multiply the number of sixteenths in an inch (that's 16 of course) by .67 (the fraction of an inch given in the table) and you'll get 10.72 sixteenths.
That tells me that if I'm measuring my cut to the nearest 16th of an inch I'll measure out 46" and another 10 1/2 sixteenths inches or 46 10/16" plus a hair as we say in the trade.
And you can see that the table gave us 46 11/16" while the calculation gave us 46 10/16" plus a hair. In other words either approach gives us something between 46 5/8 (that's the same as 46 10/16) inches and 46 11/16 inches.
What's nice about these brace length numbers is that if you measure the hypotenuse length carefully to match the numbers in the brace table you can just slap your speed-square or try-square onto the length measurement point and with your square set at 45 degrees, mark your cut. For my example, your trianglular layout of the brace, measured on the outermost edge of the bracing member, will be 33" on the two short sides and 46" on the long side.
Special Case in the Brace Table on a Framing Square: the 3-4-5 or 6-8-10 rule for Finding a Right Angle
Below is a photograph of the back of the framing square heel.
Click to enlarge the framing square photo below and you will see
in the square's back inside corner the numbers 18 & 24 next to a large 30 (red arrow), referring to the 3-4-5 rule or as I learned it the more accurate 6-8-10 rule that give measurements of the three sides of a triangle you can use to make any pair of abutting framing members into a perfect 90 degree angle.
The 18-24-30 are simply the products of multiplying 3-4-5 by 6 to apply the rule to longer lengths.
Details of using this rule are at FRAMING TRIANGLES & CALCULATIONS
Warning About the Different Inch-Divisions on the Framing Square
Why do we care about identifying the "face" or the "back" of the framing square? Because the two arms and four sides of them contain different tables of saw cut information that some texts will identify by their location on the framing square.
Watch out: you can get fouled up by different subdivisions of the inch markings on the face and back of a framing square. Remember to check the divisions as the 12ths and 10ths below can lead you to make a measuring or saw cut mistake.
Some texts say "always make your measurements using the outside edges of the framing square so that you won't get fouled-up. That advice does not work. For example, the front outside edges of the framing square measure 16ths or 8ths of an inch, depending on which blade you use, but the back outside edges of a framing square are marked in 12ths.
Our photo above shows the inch divisions on the backof a framing square:
On the back of a framing square along the outer edges of both the blade and tongue the inches are divided into 12ths (yellow arrows).
On the back of a framing square along the inner edge of the tongue (the shorter arm) inches are divided into 10ths (green arrow).
On the back of a framing square along the inner edge of the blade, inches are divided into 16ths (white arrow).
On the front of a framing square along the outer edge of the blade (the longer arm) inches are divided into 16ths
On the front of a framing square along the inner edge of the blade inches are divided into 8ths.
On the front of a framing square along the outer edge of the tongue (the shorter arm) inches are divided into 8ths
On the front of a framing sqaure along the inner edge of the tongue inches are divided into 16ths.
Framing square color and metal - do they matter?
Early framing squares were made of hardwood and carefully trued then braced into a right angle.
Modern carpenters have used steel squares and more recently aluminum framing squares for decades.
The traditional steel framing square was black while newer framing squares are often made of aluminum. Who cares what color or metal comprise your framing square? You might.
My first framing square was made of steel and was black in color with white numbers and lines. TIn the photo of my old hand tools (above), the red arrow points to this framing square while the green arrow points to an aluminum speed square whose added thickness forms a terriffifc saw guide. More about these hand tools is at DECK BUILDING & CARPENTRY TOOLS.
My old black steel framing square was easy to read in various llighting conditions, was very resistant to gouges from my rock knife when I used the square to make cuts in drywall or to make cuts in lumber as one might do to avoid chipping up wood when cross-cutting with a power saw.
This black square also got hot as hell when left flat in bright sunlight. And as the finish wore off of this tool, if I did not use it often enough it was prone to rust.
My current framing square, made by Empire Level, is made of light blue aluminum. The numbers and lines are of the same color and are quite a bit harder to read in some light conditions. This square is also easily gouged and scarred when in use. It is a bit lighter and a bit cooler in the hot sun. I miss my old square but truth is, I had allowed the old one to get a bit rusty.
Framing square number legibility improvement tip:
As the numbers and line markings on your framing square are recessed, having been stamped into the metal of its body, you can improve the legibility of a monotonic framing square (for you carpenters that means it's all the same color), by painting the whole square surface with white latex paint.
Right after you've made a horrible white painted mess of the square's surface, wipe it off before the paint dries. You'll see that some white paint will remain in the recessed numbers and grooves of the tool. The manufacturer could have done this too, but then they'd have to charge you more for the tool.
Using the Framing Square to Build Stairs
Separately at DECK STAIR BUILDING DETAILS we explain in detail how a framing square is used to layout rise and run on the stair stringers when building stairs.
How to Obtain Roof Pitch or Slope by Using the Rafter Tables on a Framing Square
Measuring the roof slope, pitch, or rise and run is easy if you've got a tape measure and more accurate still if you've also got a level on hand.
But did you know that simple data already printed on your framing square can give key roof slope and rafter data?
[Click to enlarge any image]
A long-standing use of the framing square that is missed by many new carpenters is the rafter table imprinted right on the framing square itself. This data will tell us the required rafter length for a roof of a given pitch or slope.
The rafter table on a typical framing square gives rafter length for roof slopes with a rise anywhere between 2" to 18" per foot of run.
How to find rafter length on the framing square
How would we use our framing square to measure or to calculate the slope and rafter lengths of this historic Herefordshire U.K. home?
Find the unit rise (say inches per foot) of the roof on the top line in the framing square rafter table, e.g. a 6-inch rise per foot. Read this number along the inches scale at the top of the framing square.
Directly below the 6 (inch) mark on the framing square read the required rafter length (13.42) per foot of run for a 6-inch rise (6 in 12) roof.
To calculate the required rafter length multiply the total run length (half the building width plus the width that the roof is to overhang the house wall) by this number (13.42). For example if the building is 30 feet wide, half the building width is 15 feet. If we want a 2 foot roof overhang from the front of the building wall (ignoring the thickness of wall siding and trim), we add 15 + 2 = 17 feet of total run length.
17 ft. run x 13.42 inches (per foot for a 6 in 12 roof) = 228.14 inches of rafter length, or 19 feet.
Depending on your allowance for making the ridge board and fascia board plumb cuts, you can see that you should be able to cut these rafters out of a 20 ft. 2x piece of lumber.
How to use the framing square to get roof slope
We can reverse the usual use of a framing square (finding the rafter length) to figure out the roof dimensions (or slope). Basically, for any roof dimension or slope calculation, if we know some roof dimensions or slope we can calculate the unknown.
As we explain in detail at ROOF SLOPE CALCULATIONS, the basics of plane geometry tell us about the relationship of the lengths of sides of a right triangle:
a2 = b2 +c2
the square of the length of the hypotenuse (a) equals the squares of the lengths of the opposite sides of a right triangle (b) and (c) - which is a mathematical way of saying that if we know any two roof slope measurement numbers we can compute the third.
Given the total rafter length (measure from ridge to lower roof edge) and rafter run (half the building width plus the roof overhang past the building wall) we can figure the roof rise.
If we know the roof run and rafter length, we find the roof slope by calculation or we use the framing square table (just below) and then easily find the roof rise.
For example, using the numbers from our roof framing square table example just above:
Measured rafter run RR = 17 ft. or 17 x 12 = 204 in.
Measured rafter length RL = 19 ft. or 19 x 12 = 228 in.
RR x (number on framing square) = RL
The trick here is understanding the number on the framing square is the unit-rise per foot of run.
204 x (number on framing square) = 228
(number on framing square) = 228/204 x 12in
228 / 204 x 12 = 13.412
13.412 is the unit rise in inches per foot of our example roof run. By "run" we mean the level or horizontal distance covered by the roof.
Now find the closest number to this on the framing square top row and read the inches just above. In our photo you'll see that 13. 42 is under the 6 on the inches scale. That's our roof slope in inches per foot, or 6 in 12!
Now if we still need to calculate the total roof rise, just multiply the unit rise (6) by the number of feet of run (17) and we've got the total rise in inches (6 x 17 = 102 in.) or (102 / 12) = 8.5 ft. (the total rise is 8 ft. 6 inches).
Of course if you go
to ROOF MEASUREMENTS you'll see lots of other ways to figure the total roof rise, run, or slope.
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
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 at REFERENCES you'll find more texts and articles on using a framing square and written by other experts.
Continue reading at ROOF MEASURE by FOLDING RULE or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, 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.
Chappell, Steve, "Chappell Universal Framing Square, bringing the framing square into the 21st century", [PDF], an introduction to the Model 4560M Metric Master Framer & Model 3050M Metric Traveler framing squares, (2013), Chappell Universal Square & Rule Co., LLC.
PO Box 248, Brownfield, ME 04010
207-935-3720 Website: chappelluniversal.com, retrieved 2016/04/23, original source: https://chappellsquare.com/wordpress/wp-content/uploads/2013/05/Chappell-Square-Booklet.Metric.5.3.pdf
Excerpt from product description:
The Chappell Universal Metric Framing Square incorporates a broad number of new and unique roof
framing applications, some of which have never before been available to carpenters before now. Applying
these comprehensive tables to the framing square marks the first truly unique improvement to the framing
square in over 110 years, bringing the carpenter’s square into the 21st century.
The rafter tables on the standard framing square were developed at the turn of the last century and provide
values to determine only 5 basic pieces of information: 1) length of common rafters, 2) length of hip and
valley rafters, 3) the side cuts for the hip or valley and jacks rafters, 4) the difference in length for jack rafters
for 2 spacings, 16 and 24 inches, and 5) the side cut of hip or valley. The Chappell Universal Metric Square
provides all of this information—and more—on the first two lines of the Equal Pitch rafter table alone.
Empire Level, "Rafter Square and Framing Square Diagrams" [PDF] Empire Level, Milwaukee Electric Tool Corporation, 929 Empire Drive
PO Box 800
Mukwonago, WI 53149
Toll Free: 800-558-0722
email: firstname.lastname@example.org, retrieved 2016/04/23, original source: http://empirelevel.com/squares/17453.pdf
Falconer, John (1925). Ednie, John (editor), ed. The Steel Square. Carpentry and Joinery. Vol. V. Gresham.
Heiserman, David L., Ed., "Framing Square", [web article], Sweethaven Publishing Services, David L. Heiserman, Ed., (2015), retrieved 2016/04/26, original source: http://www.free-ed.net/free-ed/Resources/Trades/carpentry/Building01/default.asp?iNum=0902
Gochnour, Chris (February 2006). "11 Essential Measuring and Woodworking Tools". Fine Woodworking (Taunton Press) (182): 75.
Lanham, Wm. The Steel Square. Bath: E. A. Lovell.
Rogers, Jim, "The Framing Square Story", [web article], The Forestry Forum, retrieved 2016/04/23, original source: http://www.forestryforum.com/board/index.php?topic=9362.0
This artice discusses use of the framing square in timber framing applications.
Schuttner, Scott (1990). Basic Stairbuilding,. Taunton Press. ISBN 0-942391-44-6
Siegele, H.H. (1981). The Steel Square. Sterling Publishing. ISBN 0-8069-8854-1..
Spence, William P. (2000). Constructing Staircases Balustrades & Landings. Sterling Publishing. ISBN 0-8069-8101-6.
Wikipedia provided background information about some topics discussed at this website provided this citation is also found in the same article along with a " retrieved on" date.
Because Wikipedia and other website entries can be amended in real time, we cite the retrieval date of such citations and we do not assert that the information found there is always authoritative. "Steel Square", Wikipedia, retrieved 2016/04/26, original source: https://en.wikipedia.org/wiki/Steel_square
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 "How to Measure Angles with a Ruler", South Dakota School of Mines and Technology, Website: http://www.mcs.sdsmt.edu, http://www.mcs.sdsmt.edu/tkowalsk/portfolio/downloads/pub_HowToMeasureAngles.pdf retrieved 10/26/2013, copy on file.
"Choosing Roofing," Jefferson Kolle, January 1995, No. 92, Fine Homebuilding, Taunton Press, 63 S. Main St., PO Box 5506, Newton CT 06470 - 800-888-8286 - see http://www.taunton.com/FineHomebuilding/ for the magazine's website and for subscription information.
Owens Corning Corporation, One Owens Corning Parkway
Toledo, Ohio 43659
Telephone: (419) 248-8000
Fax: (419) 248-5337
http://www.owenscorning.com Owens Corning is credited as the inventor of fiberglass when Owens Illinois [O-I] researcher Dale Kleist and his colleague John Thomas stumbled onto and then realized the significance of producing glass fibers in 1932. O-I formed a joint venture with the Corning Glass Works in 1935, leading to the formation of Owens Corning Corporation in 1938. More on Owens Corning's history is at
Focus, Toledo, Ohio, Owens-Corning Fiberglas Corporation, October 1988.
"A History of Innovation," http://www.owenscorning.com, 1997.
Stewart, Thomas A., "Owens-Corning: Back from the Dead," Fortune, May 26, 1997.
International Directory of Company Histories, Vol. 20. St. James Press, 1998.
"Two-Year Wisconsin Thermal Loads for Roof Assemblies and Wood, Wood–Plastic Composite, and Fiberglass Shingles [on file as Roof_Thermal_Loads.pdf] - ",
Jerrold E. Winandy
Cherilyn A. Hatfield, US Department of Agriculture, US Forest Products Laboratory, Research Note FPL-RN-0301
ARMA - Asphalt Roofing Manufacturer's Association - http://www.asphaltroofing.org/
750 National Press Building, 529 14th Street, NW, Washington, DC 20045, Tel: 202 / 207-0917
ASTM - ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA, 19428-2959 USA The ASTM standards listed below can be purchased in fulltext directly from http://www.astm.org/
NRCA - National Roofing Contractors Association - http://www.nrca.net/, 10255 W. Higgins Road, Suite 600,
Rosemont, IL 60018-5607, Tel: (847) 299-9070 Fax: (847) 299-1183
UL - Underwriters Laboratories - http://www.ul.com/
2600 N.W. Lake Rd.
Camas, WA 98607-8542
Tel: 1.877.854.3577 / Fax: 1.360.817.6278
copy on file as /roof/Roofing_Historic_NPS .pdf Roofing for Historic buildings", Sarah M. Sweetser, Preservation Brief 4, Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_3 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals-part II, Coated Ferrous Metals: Iron, Lead, Zinc, Tin, Terne, Galvanized, Enameled Roofs", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_4 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals-part III, Slate", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_5 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals-part IV, Wood", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_5 .pdf From Asbestos to Zinc, Gutters", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
copy on file as /roof/Asbestos-to-Zinc_Metal_Roofing_NPS_2 .pdf From Asbestos to Zinc, Roofing for Historic buildings, Metals- Roofing Today", Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source:
copy on file as /exterior/NPS_Preserv_Brief_16_Subs_Mtls.pdf The Use of Substitute Materials on Historic Building Exteriors ",
Sharon C. Park, AIA, Preservation Brief 16, Technical Preservation Services, National Park Service, U.S. Department of the Interior, web search 9./29.10, original source: http://www.nps.gov/history/hps/tps/briefs/brief16.htm
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: email@example.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones