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How to measure roofs DIY roof estimating

Introduction

Yes, becoming a professional roofing estimator / salesman could easily earn you well over $60,000.00 per year, with the right company. But, the main point of this DIY guide is to show you why it is important that a man who measures your roof and gives you an estimate knows how to do it correctly. This guide will also show you a few basic ways to estimate your roof from the ground by teaching you easy techinques to figure roofing squares, and estimate relative roof difficulty, which is the major factor in roof estimating.

Significance of diligent roof estimating

Let's face it, making even a relatively small mistake when performing a roofing estimate could put a huge financial hole in your wallet! For instance, being off by just a few roofing squares in the already expensive metal roofing job could cost you thousands. What is even more shocking is that there are many so called professionals in the field, who frequently make mistakes that cost consumers a lot of money. As one of many countless examples, We were recently providing a roofing estimate for the home owner who was looking to put a metal roof on his ranch type house, and we were shocked to find out that a salesman from a competing company was off by as many as seven roofing squares, when performing a roofing estimate, before us.

Roof measuring mistakes may cost you thousands

It is an undeniable truth that a Roofing project can be a great expense for the home owner. Now a metal roofing can be that same expense times three!. In metal roofing, 7 squares could easily mean seven thousands of dollars that the homeowner would over pay, have we not told him of the true size of his roof. This goes to show how easy a homeowner can be mislead by the unscrupulous quote on quote professionals.

Learning Objectives

This easy 4 step "do it yourself roof estimation guide" will show you how to figure out the number of roofing squares on your house, and teach you some basic pricing considerations for the common roof types.

Knowledge is power

Keep in mind that the purpose of this post is to arm you with the leverage of knowing what your roof estimate should be close to. (As in ballpark figure)
Knowing your roofing coverage size and scope of difficulty involved in re-roofing will insure that you are not taken advantage of by some dishonest contractor, or taken for a ride by his smooth talking salesman.

Fears of the unkown - why you need to be prepared

After all, we all dread, being taken advantage of by somebody who knows more than us about a specific field, and may use that power against us. Especially when stakes are high such as in the case of a leaking roof, when you may be under tremendous pressure trying to figure out what contractor to hire and how much you should really pay for the new roof. It is quite easy to find yourself caught off guard, unless of course you are well prepared.

Step 1 measuring your roof

First and foremost, we need to measure the roofing coverage surface area, which is measured in roofing squares.

Understanding roofing squares:

There seems to be a lot of confusion to the simple roofing concept of what the roofing square is, but actually, it is quite simple. There is exactly 100 hundred square feet in one roofing square. For example, a 10 feet by 10 feet area will give you exactly one square of roofing surface

Taking the ground measurements:

The very first thing we need to obtain the ground level dimensions of the house, or its perimetr. We can use a measure tape to obtain the length and width of the outside house walls. Later we can multiply width times the length to figure the floor level area of the house in square feet. After performing this easy multiplication we have the number that gives us plain level area underneath the roof, in square feet. Keep in mind that we need to consider roof over hangs when taking the measurements to increase accuracy and reduce errors during calculation of the roof size.

Keep in mind that houses rarely come in perfect rectangular forms, and oftentimes buildings will have funky architectural twists. So, if your house resembles a complex geometrical figure, such as several pieces of domino laying next to each other on the table, then we can find the areas of each respective piece first, and then add the sums of their areas in order to get a total area in square feet.

As an example suppose we have a rectangular house, which is 50 feet long and 30 feet wide, after multiplying both sides we get 1,500 square feet for the area of the house.

Converting area to roofing squares

In roofing industry we like to keep things simple and work with small numbers, that is why we want to convert our big number in square feet of roofing surface to a simple number in roofing squares.

Converting of the area in sqaure feet to roofing squares is accomplished by dividing the total raw area we obtained in multiplication, by a 100. For example, if we were to divide 1500 sqare feet area by 100, then we get a surface area size of 15 squares for ground measurements.

Roofing slope adjustment by roofing pitch multiplier

Now that we have derived our 2 dimensional ground measurements, we will want to convert them to a 3 dimensional roof measurements. This is the step in which a lot mistakes can be made, especially when dealing with a complex roof. Let me show you an easy way to minimize mistakes when performing a calculation of roofing slope / steepness adjsutment in order to figure out approximate actual surface of your roof.

Determining roofing pitch known as slope or steepness of the rise of your roof

For simplicity purposes I am going to sub divide roofing slopes into three categories:

Low Slope / Pitch This type of roof would have at least a 3:12 pitch, which means that roof rises 3 feet for every 12 feet of its base horizontal length. This type of roof is considered to be walkable, and easy for performing a roof installation. Note, rof our purposes, low pitch roof will not be greater than 5:12 slope of roofing steepness. Approx. average multiplier: anywhere from 1.15 to 1.25 times the number of ground squares
Medium pitch / slope The roof of this type would fall within 6:12 - 9:12 roofing slope range. Medium sloped roofs require special equipment such as roofing jacks, and planks in order to be able to perform the roofing installation. Because intermidiate pitch / slopped roofs are considered to be non walkable, they represent a higher degree of complexity, therefore they are more expensive to install. Approximate roofing multiplier: anywhere between 1.25 to 1.4 depending on the steepness of the roofing slope and how complicated / cut up our roof is. The greater the number of dormers, valleys, and endwalls, the more cut up our roof is.
High pitch / slope Roofs in this category have slope that is greater than 9:12 roofing slope. Approximate roofing multiplier variance can range from 1.41 for a simple gable roof up to 1.7 for a high slopped and cut up roof. in some cases, roofing multiplier can be even greater. Perhaps, you could use a 1.5 multiplier value to calculate the surface of a high and slight to moderate cut up roof. The high slopped roof is, perhaps, the most difficult and dangerous roofing surface to work on. You may expect to pay a higher price for this type of roof per square of installation. High slopped roofs command the use of a special protections and fall arrest equipment.

Step 4: Multiply ground level roofing squares by roofing multiplier.

For example, lets assume that our roof has a medium pitch of 6:12, and is moderately cut up with an end wall, and 2 valleys. So we decide to use a middle of the road multiplier factor of 1.35, remember that our average values could range from 1.25 to 1.4 as per table above for medium pitched roofs.

Thus we have 30 ground squares times 1.35, which equals to approximately 40 squares of actual roofing surface coverage.

The good news is that the rest is easy! The bad news is that it may also be pretty scary, but knowledge is power!

Wow you have actually read this far! You should pat yourself on the back as the hard part is now over and the fun and scary part is awaiting us...

So now that we know the actual area of our roofing surface coverage, the rest becomes fairly easy to calculate.

The actual roof prices will largely depend upon what the contractor charges and your negotiations skills. The prices you may expect to pay will be somewhat different depending on the company you are working with...

As a some sort of general guide line; I am going to throw in some numbers with the intent to show the calculation process and not the bottom line.

Lets assume that our house has 2 existing layers of asphalt shingle that require a complete tear off, clean up, and waste removal, which will run us $150.00 for our particular house.

Now let us assume that our warrantied new roof installation will be $250.00 per square (material and labor).

Thus we have: 40 squares, times 150 = $6,000.00 for the tear off and clean up. Alright, now we just have to add up the installation cost, which is 40 times 250, equals to $10,000.00.

Finally we add both results, $6,000 + $10,000 = $16,000 for a total of our roofing estimate to be.

Having read and practiced the steps outlined in this diy roof estimating guide, and learning the practical steps of how to measure your roof, You should now have a better understanding about your own roof, be able to figure out its approximate actual size in roofing squares, and define the level of difficulty involved in the roof replacement. I firmly believe that knowing these easy skills is going to provide more benefits for you, than some roof calculator software spitting the mystical numbers at you.

Good Luck! in your roofing quest

Legal Disclaimer Note:

The roofing multiplier figures provided in this post are not meant to be interpreted as the absolute accurate measures, but rather they are just some mere guess-estimate values, that were arrived at through author's experience with estimating roofing jobs, and through using the, sometimes, necessary number allowances. There are many highly complex roofs where exact roof calculations may be difficult, or even impassible to perform. As such, all the figures above are to be used for your entertainment purposes only, and to be considered as not particularly reliable. They cannot be considered legally binding, valid, or used in the court of law.

Information on this page is for your entertainment purposes only, and is not based on scientific data, or some other authoritative source.

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