Pouring ConcreteBasic steps involved in residential concrete placement
Installing concrete is a challenging job and every concrete placement is different. Size, shape, color, finish and depth of a residential project all have to be considered when pouring concrete. Once these items are decided on, the steps to place concrete are relatively always the same in regard to layout, preparation, and concrete placement. Use this guide of nine steps in residential concrete installation to get a better understanding of what takes place before, during and after concrete is placed.
Step 1- The Sale
Once the decision is made to "go concrete", most residential homeowners solicit bids from professional concrete contractors. These bids are compared, and a choice is made based on referrals, experience, price, scheduling and curb appeal of the installer. Once an installer is picked, price and logistics worked out, a contract should be presented to the homeowner. The contract should clearly state work to be completed, expectations on finish, color, and texture, price, payment schedule and warranty / guaranty information. As a side note, I recommend that the contract also contain extra information on what to expect from your new concrete slab, and any maintenance guidelines as the concrete ages. Once the contract is signed, and pre-payments made (if any), the real work can begin. Read 8 tips for hiring a concrete contractor.
Step 2 - Site Work
Before concrete can be placed, the site needs to be prepared. The area needs to be cleared and/or cleaned. Most often earth moving equipment is used to clear the area to speed the process. All grass, rocks, trees, shrubs, and old concrete needs to be removed, exposing raw earth. A sub base of a minimum 4 inches of granular fill or road base is recommended, unless the soil is very compact and stable. The sub base fill is placed and compacted over the entire area where concrete will be placed, with special attention on the edges. Proper sub base preparation is important to allow the concrete to cure properly as well as reduce the chances for heaving from expansive soils and frost heaving. Read about proper subgrades and subbases for concrete slabs.
Step 3 - Forming
Once the sub base is prepared, forms can be set. Concrete forms are made from wood, metal or plastic, and can range in height from 4 inches to many feet. For most residential concrete projects, wood forms will be used, held in place with metal or wood stakes. The forms are attached to the stakes with screws or special nails to allow for easy removal of the forms after the concrete has cured. Forms should be in good condition, be set to provide the proper slope or grade for drainage, and form clean corners where they meet each other or other structures. Special forms and or forming methods are employed for stairs and walls. Read about concrete forms.
Step 4 - Placement
The sub base is compacted; the forms are set, now it's time for the concrete. The contractor has ordered a concrete mix that meets the requirements of the slab being placed. No matter where you live the minimum cement content for any residential concrete should be 470 lb. per yard of concrete, more for colder climates. If you live in a freeze thaw climate, a minimum of 4% of air entraining admixture should be used to help prevent scaling and spalling. Small stone can be used as aggregate in the concrete if it is going to be stamped, vs. regular ¾ inch stone for broom or smooth finish concrete slabs. The concrete will arrive in a ready mix concrete truck. The drum on the back of the truck will be spinning slowly to keep the concrete inside from settling and getting hard. The ready mix truck may be able to pull up to the site and pour right into the forms. If the site is on the other side of the house or building, the ready mix truck may pour into wheel barrows or a concrete pump to get the wet concrete to the site. The contractor and crew will pour wet concrete into the forms until they are full to the top edge. While the wet concrete is being poured, contractors will be using shovels, rakes and "come alongs" (special concrete rake) to move the concrete to make sure there are no voids or air pockets. Read more about placing concrete.
Step 5 - Early Finishing
Once wet concrete has been placed into the forms, a large metal or wood board is used to screed the top of the concrete. This screeding process helps compact and consolidate the concrete, and begins the smoothing and leveling of the top of the concrete. Once the surface has been screeded, the concrete is floated. This involves using a special trowel called a float. Floats can be a small hand held trowel for edges and detail work, or a large trowel called a bull float for working large areas of the concrete surface. The surface is floated to further compact the concrete, even out any depressions or high areas, and create a smooth finish on the surface. At the same time early finishing takes place, joints and edges are worked into the concrete with special hand tools. Read more about screeding concrete.
Step 6 - Troweling
If the concrete will only receive a rough broom finish, no additional finishing may be needed after the floating procedure. If the concrete will be smooth toweled or stamped, a steel trowel finish is needed. The concrete will be left to rest until the surface begins to firm up. Once firm, steel troweling is performed to create a smooth, hard and uniform finish across the concrete surface. Steel troweling can take place by having contractors "skate" across the surface on knee boards troweling small areas at a time, or with larger trowels on poles known as "fresno" or "funny trowels". Watch a fresno tool video demonstration.
Step 7 -Finish
Once all the troweling (float or steel) is complete the final finish can be applied to the concrete. The most basic type of finish is known as a "broom finish". A special broom is pulled across the concrete surface creating a rough textured surface. Other types of finishes include stamped, textured, or smooth trowel to name a few. Read about types of textured concrete finishes.
Step 8 - Curing
Once all the placement and finishing is complete, the concrete can rest and begin to cure (get hard). The curing process lasts 28 days, with the first 48 hours being the most critical. It is recommended that a liquid chemical curing and sealing compound be applied to the concrete as soon as the finishing process is complete. The curing compound helps the concrete cure slowly and evenly, which helps reduce cracks, curling, and surface discoloration. If concrete is placed in weather below 40F, curing blankets should be used to keep the concrete warm during the initial few days of the curing process. Concrete should not be placed when temperatures will drop below 20F. The colder the temperature, the longer it will take concrete to cure. You can start to use your concrete for light foot traffic 3 to 4 days after placement, and you can drive and park on your concrete 5 to 7 days after placement. Read about curing concrete.
Step 9 - Maintenance
Concrete is a durable product, and if placed, finished and cured properly should last a lifetime. While concrete is often viewed as a NO maintenance product, consider the following simple maintenance procedures to increase the service life of your concrete. A good quality sealer is always a good idea. A cure and seal may be used the same day the concrete is placed, or a high quality sealer may be applied a month after the concrete is placed. Exterior concrete sealers can last anywhere from 1 to 5 years, depending primarily on environmental conditions. Occasional soap and water cleaning is also advised to keep your concrete looking its best. Sealing and regular maintenance will also minimize the chances from staining and discoloration caused by natural or manmade contamination.
Concrete has been around for thousands of years, and remains the most popular choice for residential patios, walkways, and driveways. When you make the decision to go concrete, understanding the basic steps—from picking a contractor to general maintenance—will make the entire process run smoother for all parties involved. Read about cleaning and sealing all types of decorative concrete.