A house plan is a construction document that guides a number of different construction efforts through every phase of building. Dimensions throughout the drawing need to be as accurate as possible to ensure every part of the home is constructed properly. Many home designers use dimension techniques that speed the design process but can cause considerable construction errors. You should avoid three dimension techniques commonly found in online plan purchases:
4" wall thickness - Most American homes are built with common 2x4 lumber. "2x4" denotes a "nominal" dimension - i.e. the name 2x4 relates to the size of the lumber (2"x4") when cut freshly from a tree. By the time the timber is dried and cut for resale, the "actual" size of a 2x4 is 1-" x 3-". To ease the design process and calculate dimensions without fractions, many designers assume walls to be 4" wide, not the actual 3-". A " may seem insignificant but those small increments can create problems at the job site. Builders always refer to the frustrating practice of "chasing fractions". Dimensions that are not accurate on the drawings force contractors to make up for the error at the job site. Even worse, if each contactor does not accommodate for these errors in the same way, critical construction issues can quickly arise. Be sure your plan uses exact thicknesses for all exterior and interior walls.
"Fractionless" dimensions - Many designers pride themselves in designing a home with even measurements - i.e. measurements without fractions. But, as mentioned above, most building materials are not evenly sized. A 2x4 does not measure 2" x 4" but rather 1-1/2" x 3-1/2". To be sure the house is built as accurately as possible, all drawing dimensions should be made as accurately as possible. Why design a space to a dimension that cannot be achieved at the job site? The only cost savings is to the designer. Moreover, many prefabricated components - bathtubs, shower stalls, fireplaces, etc. - are not manufactured on even inches. The design of the spaces accommodating these items should be dimensioned precisely. Drawings using fractionless dimensions cause contractors to "chase the fraction" at the job site (see above discussion of 4 inch wall thickness). Some contractors may even resort to "dimensioning from the drawing." This highly inaccurate practice forces a construction worker to use a ruler and calculate the dimensions of the home from a scaled drawing (usually " = 1'-0"). In this process, a measurement off by only a 1/16" can cause an inaccuracy of 3 or more inches in your home. These three inches can cause structural issues, alignment issues and may cause your home to fail final inspection. The following is an example typical of a home built with poorly dimensioned house plans. By code, the distance between the center of a toilet and a wall must be 17" or more. If this distance is less than that, you will be forced to move the toilet or the wall. In any case, you will be paying for a lot of unnecessary costs for something that could be easily avoided. Demand that your house plans are accurately dimensioned using "real" measurements of building materials.
Center line Dimensions - Many designers dimension their drawings "on-center". That means that every dimension starts and stops at the center of each wall. This tactic is done to make the designers' job much easier but can play havoc when the house is built. Understanding the practice of building homes will quickly show you why "on-center" dimensioning should be avoided as it can easily increase the cost of your home. After the subfloor is installed, framers will layout the wall positions by measuring and marking the placement of each wall. He refers to the construction documents for "on-center" measurements. The framer hooks one end of a tape measure over the exterior edge of the subfloor and places a mark at the center of the first interior wall. Since this marks the center of the wall, two more marks are required to for the inside and outside of the wall. The tape is repositioned and two marks are placed 1-3/4" to the left and 1-3/4" to the right. These represent of the wall thickness (3-1/2"). To complete this single measurement, 3 separate marks and a repositioning of the tape measure are required.
Using "edge-to-edge" dimensions - "Edge-to-edge" dimensions requires only two marks. Each distance is measured from one edge of a wall to the other edge of the wall. In fact, depending on the size of the house and the length of the tape measure, all measurements could be made without ever moving the tapes' initial position. Time is money and these seemingly minor details about a home plan dimensions can create tremendous costs during construction. For maximum cost savings, be sure your home plans use edge-to-edge dimensions that are exact and accurate - if it measures 3-1/2" it should be dimensioned at 3-1/2".
For more information about home plans, including a free 20-page publication titled "10 Things You Should Know Before Buying a Home Plan," visit http://www.avidhomestudios.com
Contact:
Craig Sherrett, Director of Sales & Marketing
AVID Home Studios, LLC
888.280.2843
http://www.avidhomestudios.com
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