3 tab math.. what is the formula for equal tabs on a roof?

Lets just say I got a 42feet of roof and applying 3 tab and want equal tabs at both ends of the roof.
Shingle is what 39 3/8 ?
Roof is 504 (42’)inches plus 1/4 to 3/8 overhang
Using a stair step pattern so 6 measured units

Believe it or not neither the ccrm or the specs guide in canada have these kinds of formulas or guides in them. I am wondering if there is a quick way to do this.

It’s the same formula for 3 tabs as it is for metal roofing & slate roofing. I’m no tile guy but it should be the same idea. Prep your roof as in paper it all & trim it out with your edge metal. Then measure the roof from one rake to the other rake, divide it by 2 & that gives you your center point. If you want overhang on the rakes add that to the numbers. Whether I’m hanging slate, installing metal panels, or nailing on 3 tabs I always run up the center. For 3 tabs & slate, I snap all my verticals & horizontals first. Then I run a pyramid up the center with a roof mechanic to my right & left following my lead, it works out great!

Thats intresting, starting from the center, thanks for the tip.

Ya bro, starting from just one side is way too slow, & what if the roof isn’t square? Then your whole roof system would be racked. Starting on one side guys are waiting on each other, crossing over each other, tangling up air lines & more. The old timers started in the center hanging slate as well & it’s worked for them for centuries & still is. The idea of 3 tabs are based on 3 pcs of slate.

I really appreciate the advice even tho I am studying for my journeymen right now I have always bin an apprentice with out a master, and a general master is what id like to become, any other tips or advice is welcome… I am currently trying to teach myself how to be fast with a stripper, hammer and 2 inch nails… in -20 lol.

No prob bro, anything to help. Gd luck & if u nd advice it’s here.

Where are you located Tyler? The program you are doing sounds interesting.

I am in rural saskatchewan, the program is …well not really a program the way I am doing it but it breaks down like this, its a interprovential journymens examination, I am able to challenge the test because of my years in service, what it will do for me is 2 things. 1. I will be able to buy restricted materials and 2. Grant a higher wage when I go and work on crews when things are slow. Other then that its just a piece of paper. I should saytho that personally it has really opened my eyes to the vast and changing world of being a craftsmen, there is a small number of items in the books I received for studying but the internet trumps it every time. I contacted the CRA to express my disconcern for the materials provided by them and they assured me s revision is in the works. Believe me man, there is a whole lot left out lol, thats government for ya tho.

Restricted materials? Damn Canada turning communist or something?

To center Tab type shingles:

First find the center of the roof, if you are going to let 1/2" of the shingle overhang the rake (like you are supposed to) make sure to take this into account when finding the center of the roof.

Make a mark a 1/4 tab length on each side of the center line, for standard shingles this would be 3".

Snap your vertical lines (your vertical lines will be 1/2 tab length apart), then measure each vertical line from each rake to make sure that the end doesn’t fall on a cut-out.

If one or both ends fall on a cutout you won’t be able to center it perfectly, just shift both lines 2" to either the left or right.
What is important is that the vertical lines 1/2 tab apart, this is your stagger.

A roof that is 32" wide, 32’ is 384".
Overhanging shingles at the rake are 1/2" on each side or 1" total, add 1" to the total length of the roof to find the center line.
385 divided by 2 is 192 1/2", so the center of the roof is 192 1/2" from each rake.
Standard 3-tab shingles have 12" wide tabs 1/4 of 12" is 3".
Working off of the center line make measurements 1/4 tab on each side of the center line, in this case 1/4 tab is 3".
So your vertical lines in this example are (measuring from the right rake) are 189 1/2" and 195 1/2".

Now you need to measure each line to make sure a cut-out doesn’t fall right on the edge.
For standard shingles which are 36" wide with 12" tabs, if your measurement falls on a 12" or 6" increment you need to shift the shingles over, both lines the same direction.
It gets a little more complicated if your rakes are out of square and you wish to have the shingles hide it.

It’s the same concept but you first need to find the plumb center of the roof.

Lol ya communist regime just we call it conservative! ahh there still better then our options. I wish our measured units were still in imperial but now I deal with a cut out that lands on 13 1/8th but ya its the concept thats important Id just rather do math that involves divisible number like 12 and 6 . Maybe I gotta brush up on my metric system. I do appreciate yous giving me the path to follow ill have the math part sorted lickity spilt.

Just curious Tyler, but what materials can’t you buy? I’m not a Red Seal certified roofer and I can buy any roofing material I want. And if you use metric enough to allow yourself to get used to it, it’s gravy.

There is 2 hurdles basically 1. Is companys in general wont follow up with the training to install the product ie being firestone certified or gaf cert. 2. Ive bin told on multiple occasions I cant buy torch on materials. It helps credibility if you get your red seal status. I was actually shocked to be teaching journeymen and apprentices on my last job about the matetial they were installing and materials they never used before, not saying they were no good cause I learned a thing or to myself… I always do, but I find it alittle unfair that a ticket is what separates my wage from my worth. I was told by a firestone rep that theres a chance I could not buy the tpo I was asking for till I schooled him in the material knowledge and app tech then he asked his boss and said sure will sell ya what ya want lol. Now there is no substitute for time spent on the roof for exp. but I sponge tech data and guides incredibly fast and thats just cause I value what I do.

Ty, a lot of them shingle manufacturers you can take the certification tests online. Real easy too, like CertainTeed & GAF. They’ll mail you your certs, a T shirt, & hat too.

Can’t remember the last time I had to worry about a 3 tab layout…

Starting in the center is fine but I’d recommend pulling a tape off one of your rakes because as someone else said, I’ve rarely seen a roof that is square. I always liked cutting 2-3inches off the full shingle because I got caught once starting with a full tab and the roof being 2inches out…lol. Your mileage may vary.

The Certainteed book is worth reading as someone pointed out, the GAF book, not so much.

The Top 4 roofing books imo are:

Copper and Common Sense 8th addition (reverecopper.com/candcs.html)
Certainteed Shingle Applicator’s Manual 11th addition (certainteed.com/Pros/Educati … Applicator)
The Slate Roof Bible (The author is a bit neurotic imo but this is still the most comprehensive book on slating to date- amazon.com/The-Slate-Roof-Bi … 0964425815)
Cedar Shake and Shingle Bureau applicator’s guide (cedarbureau.org/cms-assets/d … ec2013.pdf)

Is there any place I can get the certaintweed book? Download I mean.

Get a copy of the ARMA Residential Roofing manual. Asphalt Roofing Manufacturers Association. That is the bible that most of the manufacturers copy one way or another.


Follow the link I provided, get their number and call them. The book is free. No downloads as far as I know.