DIY Advice Blog

Yes, that really is my garage floor pictured to the right. It’s a detached garage—one of those that looks like a little cottage in the back of a small city lot. At one time it was a poured concrete floor that was probably pretty flat and crack-free. That was likely some time in the 1930s. Now it’s a dismal collection of broken chunks and miscellaneous rocks with significant dips and bumps throughout.

So what went wrong with this garage floor? There are three factors that make or break a concrete slab—literally!

1. Base: What goes under your concrete slab is just as important as the concrete itself. The best base varies according to climate and soil conditions. It may be a 16-in. layer of special base material or 6 in. of compacted gravel. To get advice, talk to a building inspector who’s familiar with soil conditions in your area. If you’re hiring a contractor to do the job, be sure the bids describe the base in detail.

I have plain old dirt under my garage floor—strike one!

2. Thickness. Most concrete garage floors and driveways are 4 in. thick, but consider upgrading to 5 or 6 in. That extra inch or two of concrete increases the strength of the slab by about 50 percent but increases the cost of a typical driveway by only $200 to $300. Be sure to ask your contractor for a bid on a 5- or 6-in. slab.

My garage floor is not even 2 in. thick—strike two!

3. Reinforcement: There are two ways to reinforce a concrete garage floor or driveway: with rods of rebar or with wire mesh. The purpose of reinforcement is to reduce cracking and to hold the slab together if it does crack. Rebar is the better choice and for most projects costs only a few bucks more than mesh. If you hire a contractor, make sure the contract specifies whether you’re paying for mesh or rebar.

No rebar or wire mesh in my garage floor—busted!

— Mary Flanagan, Associate Editor

Here are some excellent articles to help you with new concrete projects:
- How to Estimate a Concrete Order
- How to Properly Mix Concrete
- Tips to Build a Concrete Walkway

And there’s no way your garage floor is worse than mine, but if it needs some work (not total replacement), check out these articles:
- Garage Floor Resurfacing: Fix a Pitted Garage Floor
- How to Apply Epoxy Floor Paint to Your Garage
- Removing Oil, Paint and Other Concrete Stains
- DIY Concrete Crack Repair