Whether you’re just thinking about a new concrete garage floor or ready to start planning one, you likely have many questions. You might be satisfied to call a concrete contractor and let them tell you what you need. But call several contractors and you’ll probably get different ideas and estimates. Don Mason/Getty Images
Do Your Research It pays to do some research. Understanding a home remodeling project is always a good idea, whether you do it yourself or hire someone. When searching for contractors, ask good questions and recognize when answers don’t add up. Lousy concrete slabs are common. Cracks in slabs are a big headache. Some contractors say ‘concrete always cracks.’ Don’t believe it. Good concrete slabs in garages can bear weight, withstand hot and cold weather, and last many years with little or no cracks. Some garage slabs poured over 50 years ago are still solid. If you haven’t been so lucky, note that cracks in concrete can be repaired. To know what differentiates good from not-so-good concrete slabs, here’s what you need to know. Floor Level Old habits die hard. Building codes used to require the floor of an attached garage to be four inches lower than the house floor. This was to prevent spilled gasoline, vapors, and carbon monoxide from entering the house. Today’s residential building code doesn’t have this requirement. An entire house (including the garage) can be on a concrete slab poured at one height. There are still contractors and inspectors stuck in the past who suggest or insist on a four-inch step, which costs more than a level slab. If you encounter one of these people, question their wisdom and ask for evidence that it’s a legal necessity. It could be required by local building codes, but it’s not in the International Residential Code, which most local and state codes follow. Ground Preparation The biggest threat to a concrete slab in the garage isn’t what’s on top, but what might move below. Soil or base shifting or settling can cause a cracked slab. Good ground preparation starts with removing topsoil. If the soil hasn’t been ‘disturbed’, add a minimum four-inch layer of gravel or stone.Soil that has been dug up before should be compacted. The gravel or stone also needs to be compacted. Vapor barriers, essentially thick sheets of plastic, are often not required. But you really should insist on one. Vapor barrier products manufactured specifically for use under concrete are the best choice. Vapor barriers also help keep moisture in the curing concrete, slowing the curing process and strengthening the concrete as slow-cured concrete is stronger than fast-cured. The concrete slab should be at least four inches thick. If heavy equipment will rest on it, it needs to be thicker. Building codes offer requirements for the concrete mix, which vary by region and are expressed in terms of compressive strength. More water makes for easier pouring but can make for a weaker slab. Contractors can add plasticizers to create an easier flowing mix without compromising compressive strength. If you live in a cold climate, your concrete mix should probably include air-entraining agents and fiber reinforcement for a stronger slab. Wire mesh or thick reinforcement bars (rebar) have long been a component of concrete slabs. However, with proper ground preparation, a good concrete mix, and sufficient expansion joints, it may not be necessary. If reinforcement is used, it needs to rest in the middle of the slab and be anchored well. Expansion joints are necessary along the edges of the concrete garage floor and around posts or other protrusions. The resilient material used in expansion joints absorbs expansion and reduces stress. Once the concrete has been poured, it needs to be leveled and smoothed. Expansion grooves should be cut into the wet concrete for additional crack resistance. The new slab needs to be left alone. The top surface needs to remain wet while the curing process takes place. Contractors often spray curing compound or cover it with sheeting to reduce evaporation.
To ensure a durable and well-finished concrete garage floor slab, follow these expert tips:
1. Proper Curing Process: One essential step in achieving a high-quality concrete slab is the curing process.
2. Daily Water Spray: You can also offer to spray a little water on the slab every day while it cures. This helps maintain the slab’s moisture, which is crucial for its strength and longevity.
3. Consistent Moisture: By maintaining consistent moisture, you can prevent the slab from cracking and ensure a smoother finish.