Regardless of whether we are selected for a project or not, we want people to get the highest quality concrete work possible – we hate when good people pay good money for bad work! So we decided to take our passion for quality and create a list that any homeowner or client can use as a reference to make sure they’re getting a quality concrete project. We recommend they discuss the following key (yet often overlooked) factors with their Concrete Contractor:
1. Soil Conditions: The ground beneath the concrete being poured can have a massive impact on the longevity of the concrete poured on top of it. If the ground consists of clay or other fine particle soils, the water in the soil won’t drain quickly and the concrete slab above will be vulnerable to heaving and cracking from the increased water table and the freeze/thaw cycle. For this reason, we recommend a minimum of 2 inches of engineered soil (called “Road Base”) or gravel be placed beneath concrete slabs, especially driveways and floors.
In addition to the type of soil beneath the slab being of importance, proper grading and compaction of the soil are also important factors. A properly graded sub-grade should be free from any dramatic variations in depth. This is important because if the concrete varies in thickness from 4 inches, to 3 inches, and back to 4 inches, a thinner, weak spot is being created throughout the 3 inch thick area, which may result in cracking.
Proper compaction of the sub-grade is important because it settles and locks the soil together, which will prevent future settling, which will add to the longevity of any concrete work above the soil grade.
2. Thickness: A lot of the crummy concrete work we tear-out and replace is tied the thickness (or lack thereof) of the concrete slab. Some “Contractor” was either lazy or greedy and didn’t pour the concrete at a proper thickness and then the concrete cracks all over the place and fails; we see it all the time! 4″ Thickness if perfectly fine for most residential flatwork, except where large trucks, trailers, or RVs will be using the slab. In those areas, we recommend 6″ thick concrete. Personally, we recommend 6″ concrete for most driveways, because the 50% increase in thickness really improves the longevity and durability of the driveway but 4″ thickness doesn’t mean you’re getting a bad job. Just ensure that you’re getting what you pay for!
Tip: Checking the thickness before your contractor pours your slab can be a safe way to ensure you’re getting a good job and is relatively simple. Grab two helpers, a string line, and a tape measure. Have your two helpers hold the strings on top of the wood forms or the grade lines and then measure down from the string to the ground every 2 ft or so. Variations of 1/2 are no big deal; variations of 2 inches are a huge deal.
3. Rebar Dowels: We recommend that your contractor (who will hopefully be us!) installs rebar dowels where new concrete meets your home’s foundation, even if no other rebar is being placed in the concrete. This is important to prevent the slab from settling along your home’s foundation, which will help prevent water from draining toward your home’s foundation, which could cause seepage/flooding in basements and crawl spaces.
Tip: If you elect to have a rebar mat installed throughout your concrete, keep in mind that it will not prevent all cracking but will help resist bending forces and prevent uneven settling and concrete separation.
4. Control Joints: Control joints are cut into the concrete slab to create a weak point in the concrete’s surface and encourage cracking inside the joint, hence why it’s called a Control Joint. Control joints should be placed at a maximum of every 12′ in each direction. Control joints should also be run off any inside corners. It’s also important, especially when dealing with saw-cut control joints, that Control Joints are cut to the proper depth, which should be ¼ of the concrete slab’s thickness.
Tip: Customers should expect concrete to crack but for cracking to be confined to control joints. Sometimes, even if control joints have been properly placed, rogue cracking, cracking outside of a control joint, can still occur. Sometimes, the concrete just does whatever the heck it wants to!
5. Concrete Mix: Not all concrete is created equal. There are many different mixes available, which offer a wide range of strengths. Some Contractors will offer their customers a 5 bag, 3,500 PSI concrete mix in their bids, where as we always include 6 bag, 4,000 PSI concrete mix in our bids. Make sure you know what type of mix your contractor is offering, so you can make sure you’re comparing apples to apples when choosing your Contractor. Not all concrete suppliers are created equal, either; we recommend concrete from either Geneva Rock, Parsons-Staker, or, in some cases, Alta-View. We only use reputable concrete suppliers because we care about the quality of the product our customers are paying for, and most larger suppliers also offer a materials warranty on their product, which affords the customer another layer of protection.
Tip: Feel free to ask your contractor for a copy of their dispatch ticket to verify the type of concrete placed, the slump (water/cement ratio) the concrete was ordered at (slumps higher than 6″ lead to weaker concrete except when using a superplasticizer) and the amount of water the contractor added on the job (again, making sure the contractor didn’t add too much water and place inferior concrete).
6. Drainage: It is crucial for water that finds its way on to your concrete to drain away from your home/garage. A good standard rule is 1 inch of slope in every 4 feet. It’s also important to make sure that drains are placed at the bottom of outside entrance stairwells. Always ask your Contractor “Where is the water going to go?” It’s important to establish where water from your property is going, especially to avoid potential problems with your own home or your neighbor’s.
Tip: Pay special attention to the roof above the area of the work. Are there rain gutters? If there aren’t, the concrete will wear more quickly from water erosion where the water runs off the roof. Is there a Downspout in the area? A large volume of water will come down the Downspout and could lead to ice hazards and in winter time. This can be avoided by hooking the Downspout a non-perforated drain line and running it beneath the new concrete to an appropriate outlet.
7. Sealer: Sealers exists to prevent the surface of your concrete from being damaged by external factors, like salt, which can cause corrosion and spalling. By penetrating the porous surface of the concrete, sealers also prevent other substances from being absorbed, such as oil, paint, and gasoline, making clean-up a bit easier. An added bonus is that the sealers ability to keep foreign substances out also locks moisture in, keeping the concrete hydrated, which increases its cure strength. Sealer is not necessary for every job, or to even have an excellent job, but can add definitely add quality to a project.
Tip: Even if you don’t use salt on your driveways, keep in mind that the city uses it on most of the roads during the winter months, which can easily be tracked onto your slab by your car. Sealers should be reapplied every 2-3 years, depending on use, aesthetic (stamped concrete) and environment.
In summary, there are many factors that can contribute to a high quality concrete project. We hope that this information helps you, the consumer, to understand those factors and make sure you’re getting the quality that you deserve. Oh, and there is one more tip: Just hire Westar Construction to do your concrete work and you won’t be disappointed.