Garage Floor Replacement: When You Need It, How Much It Costs

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Apr 23, 2017 | Laura Firszt

Decorative Concrete Kingdom/flickr

Garage floors have a hard life. They are subject to a lot of pressure as you drive over them, as well as extremes of temperature and abuse from oil drips and substances brought in on your tires. As a result, they might end up cracking, crumbling, shifting, or (in the worst case scenario) caving in. Call a professional for consultation if you spot any signs of damage, to find out whether you need garage floor replacement or repair.

When To Replace Your Garage Floor

You may be tempted to try a repair for the concrete of your garage floor, possibly even a DIY fix using a coating such as epoxy. However, if you find that the floor has seriously cracked or crumbled, the cracks are likely to reoccur even after being patched up. Another red flag is a floor slab that has shifted or dropped.

The cause of these problems could be:

  • Incomplete prep work before the floor was originally installed, such as inadequate soil compaction or insufficient reinforcement
  • Poor concrete mix, perhaps with low quality aggregate such as iron pyrite (which has corroded over time)
  • Water damage due to either inadequate floor drainage or moisture coming from cracks in the foundation
  • Freeze-thaw cycle in winter, due to the fact that garages are often heated minimally or not at all.
  • Concrete gradually settling in place as the soil shifts
  • Salt-based snow melt brought in on car tires in winter, which gradually erodes the concrete flooring

In all the above cases, it is recommended to completely replace the floor to prevent serious problems in the future. If you are not sure how to proceed, you might want to bring in a building engineer for advice.

Cost to replace a garage floor

The base cost to install a concrete floor replacement will be approximately $6-15 per square foot. But there are a number of additional details that you’ll need to take into account, to arrive at the final price. These may include:

  • Accessibility of the garage. Your driveway may be perfectly wide enough for your car, yet too narrow for a concrete truck, requiring transportation of the concrete mix by wheelbarrow.

  • Condition of your existing floor. If the floor is a total write-off, your concrete contractor will recommend tearing it out before you proceed with the repour. Demolition, removal, and haulage of the rubble will tend to add significantly to the cost of your project.

  • Desired thickness of concrete (usually 4 to 6 inches)

  • Type of reinforcement to be used

  • Leveling of the soil if necessary

  • Additional requirements as per your regional building code -- for example, raised edges or Styrofoam installation under the concrete. Check with your local building authority before planning the project.

  • Underfloor heating for a garage that will double as living or working space, like a home office, workshop, or exercise room

Steps in the replacement process

  1. Empty the garage. Find alternative parking for your vehicles and storage for any appliances and other belongings normally kept in the garage. (This is a great opportunity to declutter.)
  2. Demolish and remove the current flooring.
  3. Excavate deeper to reach solid ground.
  4. Repair the foundation or reinforce as necessary.
  5. Install a geotextile membrane.
  6. Set up a drain for the garage.
  7. Fill in the area with gravel (3/4”) and compact.
  8. Put in place a vapor barrier.
  9. Install wire mesh or fiber mesh as reinforcement.
  10. Pour concrete for the new floor.
  11. Allow the concrete floor to cure properly before moving your car(s), bicycles, etc., as well as stored items, back into the garage.
  12. Enjoy your new garage floor.

Laura Firszt writes for networx.com.

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