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Concrete in Residential Construction
Section: Homeowner Hints
Conventional concrete has been an integral part of nearly all-residential construction in the United States for centuries. Poured-in-place concrete or concrete masonry unit construction is frequently used to construct the foundations and basements of all types of residential houses. Poured-in-place concrete is also commonly used to construct driveways, walks, and patios for the United States residential market. (Portland Cement Association)
Concrete Offers a Variety of Benefits
- Strong, durable and safe - concrete will never burn or rot and provides the best shelter against storms, hurricanes and tornadoes.
- Versatility - concrete can be colored, stamped, or stenciled to create a variety of textures and decorative finishes.
- Environmentally friendly - cured concrete is an inert material and can be recycled.
How to Choose a Contractor
- Find a reputable contractor with references demonstrating a good work history with successful home building projects of the quality you hope to build.
- Types of concrete contractors are:
a) Foundation Contractor - pours the foundation walls.
b) Flatwork Contractor - pours the slab or concrete floor. There are a growing number of ACI certified flatwork contractors. If possible, try to choose one who is certified.
- Ask for the contractor’s references: Was the project completed on time? Were the costs close to the estimate? Was the contractor easy to work with?
- Will the contractor supervise your house himself or rely on a superintendent?
- What type of contract does the contractor usually use? Several types of contracts include cost plus and lump sum. It is also important to find out what type of warranty the contractor has.
Considerations When Buying Concrete
- Concrete is shipped by the cubic yard. One cubic yard covers an area eight feet by ten feet if the concrete is four inches thick.
- Choose a quality supplier – Not all concrete is created equal. Are the dollars you are saving really being saved? Savings do not always guarantee quality.
- Mix Design - Mix designs vary by application based on four key factors:
- (i) Strength - The strongest mix without creating excess hydration resulting in additional shrinkage cracks is what’s desired. The strength of the mix used during different times of the year is important. Local building regulations will determine the mix strength for your home.
- (ii) Entrained air - Concrete flatwork that will be exposed to freezing and thawing cycles and application of de-icing chemicals should have entrained air.
- (iii) Slump - Measures how much water is in the concrete mix. If too high, it will facilitate more shrinkage cracks. If too low, concrete will be too stiff to place. Concrete slump should be between three and five inches.
- (iv) Aggregates - Must be clean and sound. Concrete mixes with larger coarse aggregate will shrink and crack less. Aggregate sizes will vary depending on your project.
Key Facts When Placing Concrete
- Drainage (Sub-grade) - Proper base preparation is important. A 3/4 inch processed stone base compacted properly will ensure adequate drainage and provide a smoother concrete floor.
- Compaction - Subsoil on which concrete is to be placed must be compacted uniformly and evenly so the slab won’t settle and won’t vary in thickness.
- Insulation - You can add different kinds of insulation to the exterior foundation to get any R-value desired.
- Reinforcement - Wire mesh in one way in residential slabs-on-grade when proper joint spacing and sub grade procedures are followed. Synthetic (or plastic) fibers are frequently used as they may prevent cracking before the concrete sets, especially in dry and hot weather.
- Thickness - Four inches is generally enough in residential placements.
- Addition of Water - Excessive water should not be added, as this will compromise the potential strength and durability of the concrete.
- Curing - Effective curing is absolutely essential for surface durability. Fresh concrete must be kept warm and moist until the mixing water combines chemically with the cement (hydration). That is what hardens the concrete and gives it its strength. Ask your contractor what steps he takes to cure concrete slabs.
- Surface Water Runoff - The surface of the finished slab should slope a minimum of 1/8 inch per foot. A slope of 1/4 inch per foot is preferred.
Note: All reasonable care has been taken in the preparation of this information. However, Tilcon Connecticut can accept no responsibility for inadvertent omissions or inaccuracies.
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