Roof Numbers

Why We Have Our House Numbers on Our Roof

As new residents of Pittsburgh, we use Google Maps frequently to learn about the city. When we moved here, one of the difficulties we had was that the street numbers shown on Google Maps did not always line up with the actual houses. Some houses had large enough house numbers that we could find the right place using Google Street View, but it was always difficult to identify the house we were looking for using Google Satellite View. When we purchased a house we wanted some way to differentiate our home when people searched for it on Google Maps. Our solution to this was to put our house numbers on our roof large enough that they could be clearly seen on Google Maps. As web developers, we also chose to make our house numbers a URL,, so that those looking for us could learn more about us, our house, and our community, when they saw our roof. We also feel that having a URL for our home will be useful when we sell our house.

How I Created the House Numbers

The process for putting the numbers on the roof of this house involved many steps, all of which highlight the many skills that Phil has developed over the years.

1) Researching Fonts and Colors

The first step in putting the house numbers on the roof was to research what type of lettering (fonts) had the greatest visibility from a distance. I learned that serif fonts (like this Times New Roman) were not as visible from a distance as fonts without a serif (like the Verdana this document is written in). I also learned that bold lettering was easiest to read from a distance. With research and experimentation the font I chose was Franklin Gothic Medium.  I also learned that colors like red were not as visible from a distance as black on white, and that the goal was to have the highest contrast between the background and the foreground.  Here is one of the tests I did comparing several recommended fonts:


2) Making Digital Mockups, Blurred and Viewed at Various Scales

I then laid out where the numbers would fit on the roof. I took a screen capture of a Google Map satellite image of our house as the basis for my mockup. In Photoshop, I created a separate image of how the numbers would look assembled as a text string in my chosen font. I then rotated and blurred these numbers to approximate the resolution of the Google screen capture. Finally, I pasted this digital number mockup onto the screen capture of the Google Map to approximate how the roof would look once the numbers were painted. I was able to scale this to varying sizes in Adobe Photoshop to approximate the varying zoom factors in Google Maps.  This images was created before the numbers were painted on the roof.  The actual Google photo of the numbers on the roof are less blurry than in this mockup.

3219 Joe Hammer aerial mockup

3) Measuring the Roof for the Numbers

When I was satisfied with the mockup and knew that the string of numbers would be visible enough to read from a Google satellite view, my next step was to measure the roof. A friend of mine helped me get a discount on a thirty-two foot extension ladder that I needed to climb from my backyard up onto the roof. It took me several hours to accurately measure the size of the roof and determine the location of each vent and chimney in order to plan where the numbers would fit. Like every row house on this block, this home is about fifty-three feet long and about sixteen feet wide, but I couldn’t use all of this space because I needed to fit the numbers between the knee walls and the vents coming up through the roof. I then input all of my measurements into a dimensioned Computer Aided Drafting (CAD) drawing of the roof.

3219 Roof_1 Model (4)

4) Creating the Digital Stencils

The next step was to formalize the digital mockup that I had made of the roof into data files that could be printed as full scale stencils that would allow me to paint the numbers. I typeset the short string of numbers in Adobe Illustrator and then used a feature called Trace Outline to create just the vector outline of my chosen font. From Adobe Illustrator I saved these outlines in a file format called DXF (Drawing Exchange Format) which I was then able to import into AutoCAD. In AutoCAD, I scaled and positioned these letters to fit within the obstructions I had documented when measuring my roof. I knew that a standard architectural printer would only output strips of paper three feet wide, so I separated the letter outlines into vertical strips that would each be plotted separately. This conversion required that I draw bridge strips to hold the edges of the stencils and the loose pieces of the stencil, like the center of the 9, in the correct position for when they would be taped down.


5) Creating the Paper Stencils

The output of the stencil needed to be converted into thirteen separate files that could be printed individually at full scale. I initially tried to output these files into Adobe Acrobat PDF with the idea that I would have them printed at Kinkos, since Kinkos cannot directly print AutoCAD files. The problems is that the maximum size image that can be output to a PDF file is only six feet long, and I needed strips of paper that were nine feet long. Even if Kinkos could print an AutoCAD file, the cost for printing these stencils would have been a dollar per square foot, or approximately $387.00.

I could have come up with a creative way to partition my stencil into smaller strips, but what I wanted to do was to output from AutoCAD directly to a plotter. By luck I read that there was someone giving away an old architectural sized plotter on FreeCycle at that time. I was able to pick up this old plotter for free, but I then had to find the resources to have it repaired, to purchase paper and ink, and to make this fifteen year old plotter work with my computer. It took me about a month to track down a replacement clutch assembly and get the old plotter working again.

Once the thirteen nine-foot-long paper strips had been plotted full size, I then cut them out with scissors, following the plotted outline of the numbers. It was challenging to handle the big pieces of paper and cut out the numbers.

6) Selecting the Materials

I did online research to learn what materials I could use on the roof that would have the highest visibility and be durable enough to withstand Pittsburgh winters and summers. My first idea was to paint the numbers in red on a white background. With further reading, I learned that the highest visibility numbers were not red on white as I had guessed, but numbers printed with the highest contrast to their background. I also learned that paints are not well suited for use on a roof because they do not remain flexible enough to be a good roofing material.

The solution for both visibility and durability was to use standard roofing materials to paint both the background and the numbers. For the background I used roofing silver, an aluminum based product that is generally used to reflect the summer heat off the roof. For the lettering itself, I used roofing tar, a material that is generally intended to seal seams in the roof. The black color of the roofing tar created a high contrast on the silver background. Together, the silver background with the tar lettering read as a white background with black lettering in the aerial photograph.

7) Preparing the Roof

The roof itself is a black membrane roof that had been silvered many years before. Half of this silver had been washed away in the intervening years, leaving the roof with a mottled appearance. To prepare my canvas, I carefully measured and taped off the area where I would paint the numbers. I knew from when I had measured the roof that no edge was straight or even and so I needed to establish my own baseline that I could work from. From this baseline, I taped off the nine foot by forty-three foot rectangle in which the letters would be painted. Inside this rectangle I used a brush to apply a fresh coat of roofing silver. I purchased roofing silver in only one gallon containers so I could carry them up the ladder one container at a time in my backpack.



8) Laying out the Stencils

Once the roofing silver was thoroughly dry, I laid out the paper stencils on the roof in the positions that I had planned them in the AutoCAD drawing. I carefully measured where each stencil went and then carefully taped down the inside edges of each letter. I knew that this would be needed because even roofing tar would tend to seep under the edges of the stencils, which could give the letters a rough appearance. I knew from my experience as an auto body painter that narrow masking tape could be curved around the shapes of numbers that size. It required patience to correctly position and handle these large stencils, which moved around even in a light breeze.



9) Painting the Roof

With the stencils taped down in place, I applied black roofing tar inside the shapes of the letters. Roofing tar is not intended as a painting media. The black tar was very hard to paint onto the roof using a four inch wide paint brush. It took me one long, full day to paint all of the letters onto the roof. I waited until the next day to climb back onto the roof and peel up all of the stencils. Even after having taped down the stencils, the roofing tar seeped slightly under the tape in places, although this is not visible in the satellite picture.


10) Waiting for Google Maps to Re-photograph the Roof

Before I started this roof numbering project, I researched Google Maps and found that they update their satellite photography every three years. Looking at the previous satellite images of my block, I could estimate that the photographs had been taken in the summer of of 2009. In the spring of that year, a large tree had been cut down on the property next to my home, and so I knew that the previous picture had been taken after that date. I understood that I needed to have the roof painted before June of 2012. I chose to paint the roof in the fall of 2011 to be assured that the house numbers on my roof would be fresh and visible in the updated satellite photograph.


3219 Joe Hammer RoofProject Complete.  My roof as seen from space!