How To Square A Deck Layout With A Tape Measure

The following diagram shows the general idea of how to square a deck layout with a tape measure. There are many ways to approach this task but here is one way which will work best for most people.

In order to make sure that your calculations are correct, it is always good practice to double check them with someone else before you publish them online or print them out.

1) Determine the length of each side of the deck. You need to know both sides because you will have to divide them later.

2) Draw a line from corner to corner along the edge of the deck. Then draw another line parallel to that first one at right angles (90 degrees). That second line represents a diagonal measurement between two points on each side of the deck.

3) Now measure the distance between those two lines. If they are exactly equal, then you have a perfect square!

4) If there is any difference, then you need to round up or down accordingly. For example if the measurements were 2 feet and 4 inches, then you would round up to 3 feet and 5 inches. Remember that rounding up or down must always be done when dividing numbers by 10.

3) Now, determine the width of each side of the deck. Divide the diagonal measurement by 2 to get the width. For example, if you measured 1 foot from corner to corner and then divided that number by 2, you would get 0.75 feet. So, multiply 0.75 feet times 12 inches equals 24 inches.

(Remember that your deck is 12 x 36 inches.

5) For example, if your measurements were 4 feet and 6 inches, you would round down to 4 feet and 0 inches. If they were 16 feet and 9 inches, you would round up to 17 feet and 0 inches.

6) Now that you have the measurements, you can proceed to step 7.

7) Subtract each measurement from the diagonal number (see chart here). In this case we are using 3-4-5 Square rule. So, you can then determine that the deck measures 24 inches less than 3 feet wide, or 0.75 feet less than 3 feet)

If your answer was not 0.75 feet, then you need to round up or down (always round down for numbers less than 1 foot; always round up for numbers greater than 1 foot). For this example, since your number is 0.75, you would round down to 0.7 feet.

3-4-5 Square Ruler

Number of Inches Number of Feet 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

For example, if your measurements were 4 feet and 6 inches, you would square them (23).

If your number was greater than 0.75 feet (such as 1 foot, 2 feet, or more), then you would round up to that higher number (2 feet, 4 feet).

Here is a chart for determining your answer:

Ans. = Answer; WidthDiff = The difference between the width and the diagonal measurement

(Round Ans. down to the nearest whole foot).

WidthDiff = 1 foot Ans. = 0.75 feet WidthDiff = 2 feet Ans. = 1.5 feet WidthDiff = 3 feet Ans.

= 2.25 feet WidthDiff = 4 feet Ans. = 2.8 feet WidthDiff = 5 feet Ans. = 3.3 feet

Now that you have this information, you can determine how to place the lines on the deck. Of course, there is no single correct way to place them but here is one way which will work well:

Width of Deck – (Ans. Then, you would add them together (4+6=10) and add the original number (4) to it. In this case, it would be 10+4=14. You would then divide that number by the number of sides in your shape (in this case, 4), which gives you 2.5, which you would then round up to 3.

So, your deck would be about 3 feet by 4 feet. The last thing to do is to divide the width by 2, which would give you the average side of a 3-4-5 right triangle which would be about 1.5 feet, or 1 foot and 6 inches. So, all together, your deck would be 1 foot and 6 inches by 2 feet and 4 feet.

Now you can place the string lines on the deck for your proportions. Let’s say that you wanted a rectangular shape with a wider top than bottom. In this case, the width could be 4 feet and the length could be 8 feet. You would then divide those measurements by the 3-4-5 proportions (12 and 8). Then, you would draw the lines on the deck to make it look like a rectangle.

If you are very precise, you could place the lines exactly between each stud. In this case, you would place one line at 1 foot and 6 inches in from the edge, and another line at 2 feet and 4 feet in from the edge.

Now that you have your lines in place, you can see that your deck is a perfect rectangle that is 1 foot and 6 inches by 2 feet and 4 feet.

Of course, you don’t necessarily have to make your deck rectangular. You could come up with other proportions that look nice to you.

The lines do not have to be straight across. For example, if you wanted a trapezoid shape rather than a rectangle, you would use the same measurements (12 and 8), but place the lines at different places. If you have a shape like this:

Then you would place your lines at 1 foot and 6 inches and 1 foot and 10 inches, rather than 1 foot and 6 inches apart. (Please note that the lines do not snap to the studs; they are just guidelines).

With this shape, as well as others, you can continue to use the 3-4-5 proportions. For example, you could make the bottom of the trapezoid 10 feet by 16 feet. Using the 3-4-5 proportions, you can see that the top of the trapezoid would need to be 5 feet by 8 feet. Then, you can repeat the same process as above to place your guidelines on your deck.

Of course, this is just one example of how you could use these proportions. There are many different ways to use them, and they all give different results.

I hope that this guide has been useful to you. I think proportions are an interesting, and often times overlooked, part of deck building. Altering the proportions can completely change the look of your deck. It is one way to make your deck uniquely yours. Thanks for taking the time to read this guide.

RaeV

__Sources & references used in this article:__

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https://www.sciencedirect.com/science/article/pii/S0039914000006536 - Determination of exponential smoothing constant to minimize mean square error and mean absolute deviation (SK Paul – Global journal of research in engineering, 2011 – engineeringresearch.org)

http://www.engineeringresearch.org/index.php/GJRE/article/view/160 - Random sequential packing in square cellular structures (M Nakamura – Journal of Physics A: Mathematical and General, 1986 – iopscience.iop.org)

https://iopscience.iop.org/article/10.1088/0305-4470/19/12/020/meta - Square slot antenna with two spiral slots loaded for broadband circular polarisation (P Sadeghi, J Nourinia, C Ghobadi – Electronics Letters, 2016 – IET)

https://digital-library.theiet.org/content/journals/10.1049/el.2016.0470 - A novel UWB band notched rectangular patch antenna with square slot (S Jangid, M Kumar – 2012 Fourth International Conference on …, 2012 – ieeexplore.ieee.org)

https://ieeexplore.ieee.org/abstract/document/6375057/