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How To Figure A Hip Roof

Figuring Out The Square Footage Of Your Roof

Hip Roof Ridge Length

While it may seem difficult at first, you can divide your roof into 10 x 10 roofing squares, a standard unit of measurement used by roofers.

But first, some terminology you’ll need to know:

  • Ridge – Where two sloped roof areas meet
  • Valley – Where two sloped roof areas meet , often with a metal channel running along the fold
  • Hip Roof – Type of roof where all sides slope downwards to the walls
  • Hip End – The triangle shaped end of a hip roof

Related: Roofing 101: What Are the Different Parts of the Roof Called?

Keep The Slope And Complexity Of Your Roof In Mind

You have to keep in mind the makeup of your roof when doing the calculation for the square footage. The steepness and complexity will change the number you multiply the footprint by.

For example:

For an easy up and over, walkable gable roof, youll multiply the footprint of the roof by 1.3 to get the square footage of your roof.

For a hip roof with a low slope, you’ll multiply the footprint of the roof by 1.4 to get the square footage of your roof.

For a steep and complex roof, you’ll multiply the footprint of the roof by 1.6 to get the square footage of your roof.

The Negative Roof Measuring Method

To find the area of a roof using the negative roof measuring method you will extend the roof line past the roof to form a single rectangle. You will then subtract the rectangular areas that lie outside of the roof.

First you need to extend the roof lines to form a single rectangle.

60 x 60 = 3600 sqft extended rectangle

You then need need to find the area of the rectangles outside of the roof area. You can see in Image 1.3 that the areas outside the roof layout are sectioned off into section A and section B. We will find the areas of these sections and then subtract them from our extended rectangle.

Area of section A = 20 x 20 = 400 sqft

Area of section B = 20 x 40 = 800 sqft

The total area outside of the roof layout is 800 sqft + 400 sqft = 1200 sqft.

3600 sqft 1200 sqft = 2400 sqft

You can see that using the negative roof measurement method gives us the same result as the positive roof measurement method.

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The Operating Cost Of Your Roofing Contractor

Every roofing contractor has operating expenses to keep their business going. These operating costs will always factor into the price of any roof work that needs to be done.

Some common operating costs are:

  • Building cost and utilities, shop and truck yard
  • Advertising and promotions
  • Payroll and payroll taxes
  • Taxes

These are just some of the fixed operating costs that it takes to run a business. No matter if a roofing company does a simple repair or replaces 10 roofs, these are the costs that have to be paid every day. No matter what work you get done or what service you need, operating expenses will always factor into an estimate or final cost.

Jack Rafters 6/12 Side

Gamer Architect: Hip Roofs: Simpler than you might think.

Similarly to the hip rafter the app will also generate a zoomable plan view with all of the rafter details

– A list of every Jack Rafter Length

– The length of the common rafter

– The bevel angles if you wanted to cut the bevels on your jack rafters, this will also be one of the bevel angles on your hip rafter

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Ridge Board Length For A Hip Roof


David Ellis of Illinois asked “how do you figure the length of the ridge board in a hip roof garage?”

David, the ridge board for a common hip roof is easy to calculate. You measure the length and width of the structure to and from the actual building line.

The building line is the point from which you start to calculate the run of your common rafters to the centerline of the roof.

I also assume you’ll be using a 2x material for the ridge board.

Subtract the shorter wall length from the longer wall length< and add 1.5 inches for the length of the ridge beam or board.

Example: Let’s say I’m building a shed that measures 10 feet by 16 feet. These are the measurements of the walls once covered with my sheathing and create the actual rectangle of the roof line.

16′ – 10′ = 6 feet

6 feet plus 1.5 inches = 73.5 inches for the ridge board

You have to add the 1.5 inches because that accounts for the king rafters that connect to each end of the ridge board just like the common rafters that touch the sides of the ridge board.

Tim Carter

How To Determine Hip Ridge Length And Wall Layout

How to Determine the Length of the Ridges on a Hip Roof and How to Lay out the Wall on a Hip Roof

The walls of a hip roof are laid out from the center of the first common rafter. The first common rafter is the one on the end of the ridge. The other rafter are laid out from this one so that buildings materials like plywood can be economically utilized. Study the drawing below. Click the images to enlarge to a new window.

The ridge of a hip roof is equal to the length of the building minus twice the run plus the thickness of the rafter stock.

Layout is from the center of the first common rafter. In the example at left the run is 10′. So this is the measurement to the center of the first common rafter. Since common rafters are shortened at the top the ridge will grow by 1/2 the rafter stock thickness at both ends or 1.5″ for nominal 2x lumber.

Sometimes a roof is a little more complex. The first step to framing a complex hip roof is figuring out the length of all the ridges. For this purpose we count hip and valley rafters as ridges. Since wood has depth we must account for this thickness when laying out and cutting rafters. Studying the next drawing will help clarify. It is an example of how to figure the ridge lengths.

Shortening– typically 1/2 the 45 degree thickness of the rafter stock- 1 1/16″ for 1.5″ thick wood.

Check out our page on how to figure the overhang or tail of a hip rafterhere.

Check out our page on common rafter terminology here.

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Measurements The App Will Generate

The app will generate just about every measurement you can think of and it will also help you visualize all of the measurements by generating an image of every rafter. Let’s start with the hip rafter.

If you are cutting bevel angles on your hip rafter we will get these angles later from the jack rafter bevel angles as they will be the same. The app also show you the backing angles if you wanted to make it really fancy and bevel the top of your hip rafter.

Lets Go Over The Details

How To Calculate And Layout Hip And Valley Roof Rafters Using Math Formula And Framing Square

Now that youve seen what the app can do let me show you all of the details. First thing that you should know is that you can zoom into any of the rafters to get a closer look at all of the measurements. When you zoom in all the way, to the overhang section of any rafter you will see that there are more measurements to be found.

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Breaking It Down So It Is Understandable

I’ll show more detailed pictures of each section as we go, but above is a basic picture of a hip rafter roof from above.

Hip rafters are the diagonal rafters that span from the ridge at the top down to the corners of the roof. If the wall plates are all square/of equal lengths then the hipped rafters would form a pyramid shape like the picture above .

The hips are in red, common rafters yellow and for hips to work on a square roof like above each member is equal.

The green arrows above show every side is equal, we’ll assume 2 metres for this example. Every common rafter is the same length and each hip rafter is the same length too .

Also, the measurement shown above in green from the corner of the roof to the center of each common rafter is equal for each as well – 1 metre.

What Is A Hip And Valley Factor

The hip and valley factor is a number that is multiplied by the run, or horizontal distance covered, of a common rafter to determine the length of a hip or valley rafter. Repeat, the horizontal distance covered, not the length, of a common rafter.

For precision, the thickness of the ridge board and any eave overhang should be taken into account when determining the run.

The hip and valley factor varies according to the slope of the roof, as shown in the table below.

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How To Figure Out The Square Footage Of A Roof

Repairing or replacing your roof can be expensive, especially if you dont know how to calculate its square footage. A wrong estimate can cost you thousands of dollars and might even delay your roof repair, leaving your home exposed to the elements. The good news is you can easily estimate the square footage of your roof with a few tools and basic geometry.

How To Use The Hip Roof Framing Calculator

How to calculate hip and valley roof

The hip roof framing calculator returns the value of the main rafter, the side rafter, the length of the hip, the height of the knee wall, and the lengths of the jack rafters.

Select the following information by using the drop downs to enter values in feet and inches.

  • Span for the main rafters
  • Thickness of the ridge
  • Roof pitch for the main rafters
  • Roof pitch for the side rafters
  • Width of the cornice

Once these values are selected the calculator will automatically fire these results

  • Run of the common rafter
  • Rise of the common rafter
  • Length of the common rafters
  • Difference in HAP
  • Run of the side rafters
  • Length of the side rafters
  • Off set of the hips
  • Length of the hips

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Finding Ridge Board Length

I will walk you thru the steps I use to find the ridge length for a 12 foot by 28 foot building requiring a simple hip roof.

At this point the pitch of the roof doesn’t matter, we need to find the run of the common rafter. Measure the width of the building and mark the exact center, 12 feet divided by 2 = 6 feet. This is the center of the ridge, now lay out the thickness of the ridge. If the ridge is 1 1/2 inches thick make a mark 3/4 of an inch on either side of this line. Measure from the outside corner to the marks that represent the ridge. You should come up with 5′ 11 1/4″.

Now measure along the length of the building from both ends and mark 5′ 11 1/4″, now if you measure between these two marks you will have the length of the ridge board.

Notice how it works out, length minus width plus 1 1/2 inches.

The Specifics Of The Program

In our online calculator of the hip roof truss system we use equal angles between the base of the roof and side and end slopes. Requested to fill in certain fields primary dimensions:

  • Linear features of the building length, width, wall parameters
  • The dimensions of the roof width and length of the base, desired height, the length of overhangs
  • Data for calculating rafters of a hip roof and battens width, thickness and angles
  • The settings of sheating – OSB board, are only for soft types of roof
  • Roofing sheets and information on roofing underlayment.

Recommended Reading: Adding Eaves To Gable End

Adding And Calculating The Ridge Length

Hipped roofs are rarely square like the example above. The picture below shows the same roof, extended length ways with the addition of a ridge. It is basically a gable roof with half of the hipped roof above stuck on each end.

For that reason, we can use the same common rafters all the way around it. We’ll assume the new length of the roof below is 3.4 metres.

To calculate the length of a ridge in a hipped roof you simply subtract the width away from the length. Importantly though, you must add the thickness of the ridge back on to that measurement, so we can use the same common rafters already measured .

How to calculate the length of the above ridge:

Length – Width + Ridge thickness

The ridge in this example would be 1.35 metres long.

Calculate The Square Footage Of Your Roof

How To Frame A Hip Roof – Including A Common Rafter Review

Now that you thought about the slope and complexity of your roof, youre ready to learn how to calculate the square footage of your roof.

To get a rough estimate for your roofs square footage, youll use this equation:

For example, if you have an easy up and over, walkable gable roof and a house that measures 56 feet lengthwise and 28 feet widthwise, your calculation will look like this:

1,568′ =

x 1.3

2,038 = square feet of roof area

Using this equation wont be 100% accurate, but knowing your roofs square footage is a great jumping-off point to learn how much youll have to invest in your replacement.

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Explanations Of The Results Of Hipped Roof Calculations

After you enter the numbers, hit “Calculate” and get the following:

  • Calculation of the hip roof truss system with a detailed drawing of the whole structure in general and final data,
      • The sizes of all the rafters of a hip roof separately
      • The calculation of counter-battens and roof battens
      • Calculation of inferior purlins or wall plates in a detailed final drawing.
      • Calculation of the hipped roof area .
  • The total volume of lumber for the rafters, battens

  • Drawings of all types of rafters separately

  • The hip roof layout diagram

  • Drawings of the complete hipped framing system from different angles

  • Interactive 3D model of a hip roof for clarity.

  • The lengths of hip, jack and common rafters are given in the calculation results and drawings with overhangs .

    With our program you do not need to think about how to calculate the hipped roof area for the purchase of necessary materials, all data is available in our calculator Save to bookmark, share with friends – useful tool will be always at hand.

    Calculate hip roof online – save time and money for necessary materials purchasing, get a detailed list of all hip roof elements dimensions for your future roof construction.

    Hip Roof Area Calculator

    Hip roof is a roof with a sharp edge or edges from the ridge to the eaves where the two sides meet. Here is the online hip roof area calculator which helps you calculate the hip roof parameters such as roof rise, common and hip rafters length and roof area based on width, height of roof base and the roof pitch . Calculating the dimensions of the hip roof rise and area would be very easy and time saving using this calculator.

    Recommended Reading: Add Overhang To Side Of House

    How To Calculate Irregular Hip Rafters With The Redx Roof App

    There are several ways to calculate hip rafters and jack rafter lengths. I’ll cover the most efficient method i’ve found, which uses the RedX Roof App to automatically calculate every measurement.

    Measurements needed

    The measurements we will need to to enter into the app are as follows, We will go into details on all of these later on.

  • Roof pitch 1

  • The Bottom Run of the common rafter.

  • Jack rafter spacing

  • These 4 values are all we need to generate a 2d plan view of our corner hip That will look like the image below.


    There are many things we can customize like

    – Hip rafter thickness

    – Facia depth

    – How deep the birds mouth cut will be

    I’ll go over what all of those mean later on in the post, I just want to show you all of the other measurements the app will generate before we get into to many details.

    Sometimes You Need To Do A Quick Calculation To See If The Numbers Stack Up We Get It

    How to Determine Hip Ridge Length and Wall Layout

    Our table of roof slope factors will help you do the maths when it comes to roof areas, sheet length and hip length. Remember, these methods are for quick estimating purposes only. Accurate measurements must be taken from the actual roof frame before ordering roofing and rainwater products.

    As an example, take a typical hipped roof where all four roof sections have the same slope and all hips are of equal length.

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    Squares Rectangles And Triangles

    Nearly every roof, no matter how simple or complicated, can be broken down into squares, rectangles or triangles. You can draw lines on your diagram from the ridge to the eaves to make triangles out of the hips. This will leave you with four triangles for the hips, two rectangles for the rest of the hip roof, and another rectangle for the lean-to roof.

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    Finding The Pitch Of The Hip

    Once youve temporarily supported the ridges with a few common rafters, you can lay out the hip rafter. I do the layout on a sheet of plywood. Using one corner, I start by drawing the angle of the hip and then develop this line into a fullsized plan view of the roof corner. From this drawing I can pull exact measurements for my bevel cuts.

    Hip angle. Using the framing squares 12th scale, find the hip angle as shown in Figure 3A. Draw a diagonal line between 9 feet on the tongue of the square and 7 feet 6 inches on the blade. This gives the angle of the hip rafter.

    Unit run of the hip. In a hip roof with equal pitches, the unit run of a hip or valley rafter is 17 inches for every 12 inches of run in the main roof. For example, in an equal hip roof with an 8 / 12 pitch, the pitch of the hip rafter would be 8 / 17. But here it will be different, since the hip rafter doesnt lie at 45 degrees to the commons.

    The pitch of the unequal hip rafter can be expressed in relation to either the main roof or the secondary roof. Since you need only one set of numbers to lay out the cuts, lets work with the main roof, which has a unit rise of 8 inches.

    Unit run of hip = 15 5/8 in.

    So now we know the pitch of the hip rafter in relation to the main roof:

    Hip pitch = 8 / 15 5/8

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