How to find surface area of a sloped roof?

[Anonymous]

Hello.

I work for a roofing company and am using AutoCadLT. Is there a tool (or extra command for AREA) to find the surface area of a pitched roof, if given the plan dimensions and the rise/run?

[imadHabash]

Hi,

does this link help . >> Click <<

Regards,

[gotphish001]

No tool that I'm aware off. You also need to get the measurements off of 2 different elevations views. If you knew all this then it might help another beginner. 

Example see image: To find the area of the roof side that I have hatched with shingles. You can't just measure the west elevation and multiply the sides. "A multiplied by C" is wrong. Because the C side really is longer because it is going away from you. It only looks that length because of your perspective. To find the area of the shingled roof you need to do "A multiplied by B" B and C are actually the same side of the rectangle but the B measurement is actually how long it is. C is just how it looks from that perspective. If you only have a floor plan then you'll need to draw some simple elevations like mine to get the roof area. The B side would just need to be drawn at whatever your slop is. Don't forget to add in any overhangs on your simple elevations as that could add an extra couple feet to the length of that side. They can still be really basic like my examples though.

[Anonymous]

Thanks but, as mentioned, all of our drawings are in plan view. Hoping for an input option for the AREA tool, where I can take total surface area, then it factors it by the rise/run I am given.

[Anonymous]

Thank you, but these inputs require more information than I am given. All I have are the perimeter roof plan measurements and the pitch. I did copy their Slope Correction Factor Chart, though

[john.vellek · Accepted solution]

Hi @Anonymous,

One way to do this is to create a block of each part of the roof from plan view. Then you can insert the block using ax or y scale factor depending on the roof pitch.  The scale can be calculated by the amount of the sloped distance vs. then plan length.

For instance here is a little chart I threw together.

Once the blocks are inserted with the scaled depth, you could then use a boundary (BO command to quickly find the perimeter and the look in the properties panel for the area.

This might be more work than its worth but it might be worth your consideration.

Please select the Accept as Solution button if my post solves your issue or answers your question.

[gotphish001]

That's a sneaky way John. At first I was thinking to make an excel sheet with some values plugged in. That's basically what you have going on with a block. 

@Anonymous I know you said you only had the plans. That is why I said you would need to draw some simple elevations like I showed to get the length of the sloped side.

I did find this with a simple google search. It will do what you want for simple roofs.  https://www.improvenet.com/r/roofing-calculator

[john.vellek]

Hi @gotphish001,

That is nice little calculator but it would (I think) only work for rectangular surfaces.  The method I suggested should accommodate roofs that are interrupted by hips and valleys.  Let's see if they OP will give it a try.

[Anonymous]

I will give this a try but it does sound bit more involved than I was hoping. I deal with 100s of roofs per week, in a wide range of shapes, sizes, hips, and valleys. The conversion chart will come in handy for hand calcs, though. Thanks!

[Anonymous]

Hi there.

We created a website with this exact purpose - to calculate the surface area of a roof.

https://roofing-area-calculator.com/

We have many roof shapes with or without dormers and it is dead easy to calculate the surface - we only need length, width and rise of the roof.

We also have other tools like shingles calculator 

https://roofing-area-calculator.com/roofing-materials#shingles-calculator

or a pitch calculator

https://roofing-area-calculator.com/roof-pitch

Everything here is free and easy to use (we hope).

Please let me know if you can see anything odd or need some more tools we might implement them.

Note - I am not a native english speaker so I might have messed up some texts and terms - please let me know.

Best regards,

Alex