Do You Need New Concrete? The 4-Inch Rule for 2-Post and 4-Post Lifts
It is the nightmare scenario: You spend $4,000 on a new car lift, spend a Saturday installing it, raise your prized car into the air-and then hear the sickening sound of concrete cracking.
The fear of your floor failing is real, but it is also easily avoidable if you follow one simple rule.
Most residential garages in the US are poured with standard “3,000 PSI” concrete at a depth of 3.5 to 4 inches. For a regular car, this is plenty. But when you start applying the heavy forces of a commercial-grade lift, that 4-inch mark becomes the difference between a safe shop and a disaster.
In this guide, we will give you the definitive “Go/No-Go” numbers for installing a lift in a standard garage, and tell you exactly what to do if your floor is too thin.
The Concrete Traffic Light: Which Lift Can You Install?
Before you drill a single hole, you must know if your floor can handle the stress. We have simplified the complex ALI (Automotive Lift Institute) standards into a simple “Traffic Light” system.
Find your concrete depth below to see which lifts are safe for your garage.
GREEN ZONE
Concrete Specs
4.25″+ Depth
3,000 PSI (Cured)
Safe to Install?
Your floor is strong enough for heavy-duty anchoring.
Recommended Lift
2-Post Lifts (For Repair)
4-Post Lifts (For Storage)
YELLOW ZONE
Concrete Specs
3″ – 4″ Depth
Unknown PSI
Safe to Install?
Do NOT install a standard 2-Post lift here. The anchors may pull out under load.
Recommended Lift
4-Post Lifts (Safe)
(These don’t require anchors)
RED ZONE
Concrete Specs
< 3″ Depth
Asphalt / Pavers
New Pour (<28 Days)
Safe to Install?
Drilling is dangerous. Anchors will fail immediately.
Recommended Lift
Portable Lifts
Free-Standing 4-Post
⚠️ Critical Warning: Post-Tension Slabs
Do you see a stamp on your garage floor that says “Post-Tension”? If so, DO NOT DRILL. Cutting a tension cable can snap through the concrete and cause serious injury. You must use a free-standing 4-post lift or hire a professional to X-ray the slab first.
Why the Difference? (The Physics of Falling)
You might wonder: “Why is a 4-Post lift safe on thin concrete, but a 2-Post lift isn’t?”
It comes down to Leverage vs. Compression.
2-Post Lifts (The “Tipping” Force)
Imagine holding a sledgehammer with your arm fully extended. It feels heavy, right? That is what a 2-post lift does to your floor. The car is balanced in the middle, creating massive tension that tries to rip the bolts out of the ground. If the concrete is less than 4 inches thick, the anchors will fail, and the lift will fall.
4-Post Lifts (The “Table” Force)
A 4-post lift works like a table. The weight pushes straight down (compression) into the floor. Concrete is incredibly strong under compression. Even a thin 3-inch slab can easily support the weight of a stacked Ferrari and SUV because the force is spread out, not pulling up.
The $5 “Drill Test” (How to Know for Sure)
Don’t have the blueprints for your house? You can test your slab depth in 5 minutes.
Buy a Masonry Bit: Get a standard 6-inch masonry drill bit ($5 at Home Depot).
Pick a Spot: Choose a discreet spot in the garage (away from the edge/wall).
Drill: Wrap a piece of tape around the drill bit at the 4.25-inch mark.
The Verdict:
If you hit dirt before the tape hits the floor: You have Thin Concrete. (Buy a 4-Post).
If you hit the tape and are still drilling concrete: You are Safe. (Buy a 2-Post).
“My Concrete Failed the Test.” What Are My Options?
If you did the drill test and hit dirt at 3 inches, don’t panic. You do not need to rip up your entire garage floor. You have three distinct paths forward:
Option 1
The “Switch to Storage” Strategy
(The Easiest Fix)
If your heart was set on a 2-Post lift but your concrete is too thin, the safest move is to switch to a 4-Post Lift.
Why: As mentioned above, 4-Post lifts generally do not require anchor bolts for stability (though they are recommended). They rely on surface area and compression.
Verdict: This is the only safe way to lift a heavy vehicle on 3-inch concrete without construction work.
Option 2
Cut and Pour
(The “Pad” Method)
If your heart was set on a 2-Post lift but your concrete is too thin, the safest move is to switch to a 4-Post Lift.
The Fix: You cut two 4ft x 4ft squares out of your existing floor. Dig down 12 inches. Pour new, high-strength (3,000+ PSI) concrete with rebar reinforcement.
Verdict: This is the only safe way to lift a heavy vehicle on 3-inch concrete without construction work.
Wait Time: You must wait 28 days for the new concrete to cure before installing anchors.
Option 3
The Scissor Lift
(The Low-Profile Fix)
If you just need to do wheel and brake work, a portable Scissor Lift or QuickJack frames generally spreads the load out over a wider frame than a 2-post lift.
Verdict: Great for maintenance, but useless for parking/storage.
3 Deadly Myths About Concrete & Lifts
Myth #1: “My Epoxy Floor Makes the Slab Stronger.”
False. Epoxy is a cosmetic skin. It adds zero structural integrity. In fact, when installing a lift on epoxy, you must be careful not to crack the coating.
Pro Tip: Drill your anchor holes through the epoxy. Do not try to “glue” the lift down.
Myth #2: “I’ll Just Use Longer Bolts.”
False. If your slab is only 3 inches thick, buying 7-inch anchors won’t help—you’ll just be anchoring into the dirt beneath the garage. The holding power comes from the friction against the concrete. If there isn’t enough concrete to grab, the length of the bolt is irrelevant.
Myth #3: “I Can Install on Asphalt if it’s Thick Enough.”
FALSE. Never, under any circumstances, install a car lift on asphalt. Asphalt is a liquid (a very slow-moving one). Over time, the bolts will loosen, and the lift will topple. Concrete is mandatory.
Frequently Asked Questions (FAQ)
Q: Can I install a lift near a crack in the floor?
A: Industry standard is to stay at least 6 inches away from any significant crack or expansion joint. If your preferred spot is right on a crack, move the lift or use the “Cut and Pour” method.
Q: How long does new concrete need to cure before installing a lift?
A: 28 Days. Do not rush this. Concrete may look dry in 3 days, but it hasn’t reached its full PSI strength until the 28-day mark. Anchors will pull out of “green” (uncured) concrete.
Q: What is the minimum PSI for a BendPak lift?
A: Most BendPak 2-post lifts require a minimum of 3,000 PSI. Most residential builds meet this spec, but older homes (pre-1990) should be tested.
Conclusion: Safety First, Lift Second
A car lift is likely the heaviest piece of equipment you will ever own. It holds a 5,000-lb vehicle over your head. This is not the place to “hope for the best.”
Still not sure about your floor? Take a photo of your garage setup and email us at support@carliftlab.com. We can help you look for signs of post-tension slabs or structural issues before you buy.