Masonry Takeoff Overview
Concrete block or CMU (short for concrete masonry unit) is widely used in crawlspace foundations and basements in the south, and as the exterior walls in coastal regions subject to high wind. In the case of CMU homes, the second floor is commonly built in wood frame for cost savings. The same wood roof trusses/rafters, sheathing and interior lumber walls are commonly used in both wood frame and CMU construction.
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You will receive editable Excel Spreadsheet Material lists with a detailed breakdown of the quantities and usage within the model. With Archidiem, you get 3-in-1 Reports automatically.
In addition, you will receive color coded markups of your PDF plans useful for auditing the areas we considered for your takeoff.
Concrete Block Construction (CMU)
CMUs are cement blocks made from a mold in a factory. Typically, a residential exterior wall is made from CMUs that measure 8″ x 8″ x 16″ and is 80 % hollow. The CMUs are laid on top of the slab or concrete footing in an interlocking staggered method and the wall is raised to its desired height. Mortar holds each block in place.
Once the CMU wall is constructed, some of the hollow block cells are filled with concrete in the cells that hold vertical rebar and other shear resisting rod or cable systems. The top of the wall consists of a “poured in place” concrete lintel that ties everything together.
CMU walls provide better sound proofing but is not as energy efficient as a wood framed home.
Concrete Block (CMU) Foundation Walls
Concrete masonry is used to construct various foundation wall types, including full basement walls, crawlspace walls, stem walls and piers. Concrete masonry is well suited for below grade applications, because of its strength, durability, economy, and resistance to fire, insects, and noise. The modular nature of concrete masonry allows floor plan and wall height changes to be easily accommodated as well. Concrete masonry can be used to provide a strong, durable, energy efficient and insect resistant foundation for all building types.
Basements allow a homeowner to significantly increase usable living, working, or storage space at a relatively low cost. Old perceptions of basements have proven outdated by state-of-the-art waterproofing, improved drainage systems, and natural lighting features such as window wells. Other potential benefits of basements include room for expansion of usable space, increased resale value, and safe haven during storms.
Historically, plain (unreinforced) concrete masonry walls have been used to effectively resist soil loads. Currently, however, reinforced walls are becoming more popular as a way to use thinner walls to resist large backfill pressures. Regardless of whether the wall is plain or reinforced, successful performance of a basement wall relies on quality construction in accordance with the structural design and the project specifications.
CMU Stemwalls for Crawlspace Walls
Unlike basements, crawlspaces are typically designed as unconditioned spaces, either vented or unvented. Although most building codes require operable louvered vents near each corner of a crawl space to reduce moisture buildup, research has shown that the use of a moisture retardant ground cover eliminates the need for vents in many locations. If the crawlspace is vented, the floor, exposed pipes and ducts are typically insulated. If unvented, either the walls or the floor above can be insulated. Unvented crawlspaces must have a floor covering to minimize moisture and, where applicable, soil gas entry. A vapor retarder (typically 6-mil polyethylene, PVC or equivalent) is good practice to minimize water migration and soil gas infiltration. A 2 ½ in. concrete mud slab is commonly used when a more durable surface is desired for access to utilities. A thicker concrete slab may be desirable, particularly if the crawlspace will be used for storage. A dampproof coating on the exterior crawlspace wall will also help prevent water entry into the crawlspace.
CMU Stemwalls for Slab on Grade
A stemwall with slab on grade supports the wall above and often also provides a brick ledge to support an exterior masonry veneer. Because the wall is exposed to soil on both sides, waterproofing or dampproofing coatings are generally not required. Stemwalls are typically insulated on the exterior of the masonry. If insulated on the interior, it is important to place insulation in the joint between the slab edge and the foundation wall to avoid thermal bridging.
CMU Foundation Piers
Foundation piers are isolated structural elements used to support the building above. Structural design ensures the piers are sized and spaced to carry the necessary building loads. Piers typically are in enclosed crawlspaces, so recommendations for moisture and soil gas resistance for crawlspaces should be followed for piers as well.
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