How to Read Shop Drawings

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Shop drawings are necessary for building structures.

Shop drawings are blueprints designed for construction purposes. Shop drawing language incorporates the use of various numbers, symbols and abbreviations that make it difficult for a layperson to read. Architects, engineers and construction professionals master the language to keep shop drawing measurements and blueprints universal. Lay people can begin reading shop drawings after comprehending several important references.


Step 1

Examine the plate size and fitting. Plate sizes are indicated by a specific numerical dimension and an equal sign. For example, the top plate size is "2x2=". The numbers indicate the square inch size of each plate. The "=" sign appears next to the numbers horizontally, vertically or at an angle. The position of the "=" sign indicates how the plate physically fits on the beam. Twelve plates are typical on one truss.

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Step 2

Notice the slope. The slope is located near the middle of the drawing on the left hand side. The slope, "8/12," for example, indicates how many inches – 8 – the height of a truss will rise per 12 inches.

Step 3

Look at the height of the object. The height is located at center, on the far left side of the drawing. These dimensions are the only numbers on the drawing written vertically on the page.


Step 4

Figure out alphabetical abbreviations. Loading abbreviations, for example, are located in the bottom left hand corner of shop drawings. Four major abbreviations – TCLL, TCDL, BCLL, BCDL – are important to know. Top Chord Live Load numbers – TCLL, for example – denote the poundage per square foot of temporary weight the top joints are capable of holding. Top Chord Down Loads indicate the poundage per square foot of permanent weight top joists. BCLL and BCDL stand for Bottom Chord Live Loads and Bottom Chord Down Loads.

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