Drawing An Architectural Roof Plan

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If you’ve ever looked over a set of house plans, you should find several pages containing a floor plan or plans, electrical plan, exterior views or elevations, etc.

The roof plan is sometimes overlooked on some plans but it is actually a very important feature to a full set of plans. A roof plan is a view from the top of the house that shows the geometry in plan view of the roof. Drawing a roof plan isn’t all that hard if you’ve already got a grasp of basic drafting. This type of drawing is based on the floor plan and the exterior elevations of the house.

If you are using a drafting board, it’s a simple matter of placing the completed floor plan or plans under a transparent sheet of paper, tracing the perimeter exterior walls, and then measuring beyond those walls using an architectural scale to where the overhang (fascia) of the house will be. Then projecting lines from the exterior views you can determine where one part of the roof line comes together with the other roof lines in peaks and valleys.

If we were using a CAD system, we would do the same thing as using a drafting board. A line would be drawn around the parameter of the home, and then offset the distance of the overhang. You would then measure to each individual peak of the roof and draw a line representing it.

Then, if the roof has more complexity to it like valleys, crickets which are little roofs that shed water from a possible water or snow trap, and any shed roofs would be drawn using the same method. Once this drawing is completed, it can be used to draw a rafter plan showing how the roof system goes together and give us the right geometry to make sense of the roof construction.

Below is a step by step way to draw a simple roof plan using Computer Assisted Drafting (CAD):

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Above is a basic floor plan that we would use for the basis of our roof plan. Notice the lines drawn outside the perimeter of the house. With the one above, the lines are 16″ beyond the perimeter.

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With this on your screen, draw a line in the center of the porch vertically and a horizontal line in the center of the main rectangle as shown below!

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Now draw a -45 degree line on the left side of the porch intersection and a 45 degree line on the right side of the porch intersection.

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The next step is simple! Clean it up!!! Trim the line from under the porch, fillet or trim the vertical lines on the porch so that they join the main roof and join the three lines inside the porch roof to have an image as shown below.

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Looks like a roof now, doesn’t it? The next and last step is to place the full perimeter walls in the proper location under the roof. Best way to do this is turn the Floor Plan layers on and trace the perimeter while still in the roof layer. Once traced, turn the other layers back off and change your traced lines into a hidden or broken line as shown below.

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Scale this image down by half using your scale command. Then insert the Roof Plan on your Floor Plan Sheet. Label it as Roof Plan and your Scale is 1/8″=1′-0″. Place a leader on the main center line labeled peak, a leader on each side of the angled lines of the roof and label them valley, a leader on the center line of the porch roof and label it peak. Then finally place a arrow leader at the overhang and label it as 16″ overhang as shown in the images below and the task is complete!

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Some drafters make their living drawing specialty plans like the roof, electrical, plumbing, and HVAC plans by hiring themselves out to designers and architects. This saves these professionals from having to draw the extra complex items on the plans in order to spend more time designing.

Would you like to learn to draw complete House Plans using a CAD program. If you do, go to http://houseplandrafting.us/ and get more information.


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I’m your host and webmaster. I’m someone who enjoys life to it’s fullest and love programming, drafting, farming, and an ordained Baptist pastor and sheriff’s department chaplain.



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