Can you answer some questions about replacing a garage floor?
We have an existing detached 3-car garage. One-third of it has a poured concrete floor, which is in good condition. The other two-thirds is a combination of patio stones, dirt & gravel. We would like to pour a concrete floor to meet up with the existing floor and have a number of questions. The space to be poured is approx 18 by 24 feet. Do we need a building permit? (Structure is old, no land survey available, no space between our garage and the neighbor's) How do we choose a contractor? What should we know about materials - concrete type, psi, gravel size, how much of each, screening, etc. ? What should we expect to spend on a job of this type? How long would it typically take to excavate, pour, and seal? We have had a number of quotes ranging from $3,200 (from a contractor who only does concrete work) to up to $8,200 from a general contractor. We would really appreciate some guidance. We have asked friends & family, but no one has any contractor recommendations. Help!
Expert
Maestro
Building permits are generally needed for structural changes to a building. Pouring a non-structural concrete floor likely does not require a permit, but speak to your local building department if you want to be absolutely sure. The easiest way to get a good concrete floor is to get a good contractor. Find 2 or 3 contractors known for high-quality work, with established reputations. If you've tried friends, family and neighbors with no results, try the local home builder's association. Obtain proposals and make sure that all are bidding on the same work. Compare what they plan to do, and quantity of materials they plan to use. Insist on a written contract which includes any guarantee offered. If possible, hold back some money until you're completely satisfied with the job. If you're concerned about timing, as for start dates and how long the work will take. Ask for lots of references and visit other projects the contractor has done. If possible, talk to former clients. With respect to methods and materials, a few key things to look for are:
- Is the floor slab to be reinforced or not? Reinforcing is an upgrade, but not a necessity.
- The concrete should have a minimum compressive strength of32 MPa after 28 days.
- Concrete slabs should be poured on a well-compacted layer of gravel 4" to 6" thick.
- If a surface sealer is to be applied to the concrete, a moisture barrier should be installed beneath the slab to reduce the potential for spalling.
- The concrete should have 5% to 8% air entrainment.
- The slab be sloped to drain water to the exterior.
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