Concrete floors are a critical structural part of a lift, and ceilings & rafters must not interfere
Concrete floors
When properly installed the cement floor becomes an integral part of a lift. The square formed by the left and right columns and the floor form a box that really pushes the lift and vehicle up. Your vehicle’s weight load is transferred and supported by the cement floor. Steel floors may be acceptable but really nothing but concrete works properly and safely. The obvious truth here is that your concrete MUST be within specification. Any two post lift must be installed on a 4-1/2in thick cement slab of minimum 3,000ft/sq/in concrete. 3/4X5-1/2″ anchors must be at least embedded 3-12″ into the slab. the anchor must be torqued to 150ft/lbs initially. Anything else is UNACCEPTABLE. You can make it a little better, if you like.
To make a better slab: Build a solid base of clean dirt and 1 or 2 inch rock, tamp to pack your base hard before you pour the concrete. Pour your floor 5-1/2″ thick, using 3,500 psi, fiberglass reinforced concrete. Anything more for a car/medium truck shop is wasted money, it will only make the concrete supplier wealthy, it will serve NO other purpose.
How to determine if an existing floor is adequate
Determining the structural integrity of your floor is fairly simple. First, if your home, building or commercial property was built in the last 75 years by a professional builder, who obtained a building permit to construct the structure it is likely perfect. Building and fire codes are uniform across the USA so all honest people abide by them. In my 60 plus years of experience, substandard work has shown up less than 1% of the time.
Nature can cause problems of course so if you suspect a problem have an expert check it out your local building code/permit department has a list of approved inspectors, hire one of them to check your place.
Otherwise here are some bewares: A homemade slab where concrete was mixed by hand, especially by do-it-yourselfers, best be checked. A building erected by iterate contractors from out of town, often can be substandard. “Spec buildings” by “Spec Builders” are usually “fast buck” artists who are cheaters in every way. If your building was “way less money” than anybody else chances are that they “skimped” on the concrete. Looks good does not mean good regarding floors.
If your floor is below acceptable integrity
It must be repaired – upgraded – before installing a lift of any type. I have done numerous upgrades of this sort. It is a job, however, it is not as bad as other problems. This is the proper procedure to make it right:
When floor is substandard
For passenger car lifts up to 10,000 pound capacity, pour a 4”x4”x5.5” concrete pad under each column. Keyed 6” under the existing floor and tied in with rebar.
For truck lift of 15,000 or 18,000 pound capacity pour a 6”x6”x6” concrete pad under each column. Keyed 6” under the existing floor with rebar ties.
When pouring new concrete for a lift it is strongly recommended that 3,500 PSI concrete with fiberglass reinforcement be supplied. No rebar or mesh need be used in the general slab as they might interfere with drilling of anchor holes. In that case you could face incurring more expense if a coring driller is needed.
IF YOUR FLOOR IS SUSPECT
Here is the likely situation in your case. If your floor was built by a professional, experienced contractor, it will likely work fine. If the floor was done by “do it yourself-ers” it may be inadequate. You will need to know before you continue.
If it is deemed not acceptable, this is what you do. Using the manual I will send to you, find your lift model’s blueprint (dimension chart). Mark on your floor the exact spots where your 2 or 4 posts will be. Then mark the spots with a large square that is 48 inch by 48 inches with the original markings in the center of each one. You now have squares on your floor where the 2 or 4 posts will eventually be. The post plates are about 10 inches by 10 inches for 4 posts or 24 inches by 24 inches for 2 posts. Those squares you drew on the floor are 48 inches by 48 inches. This is what you must dig up.
New you saw cut those squares thru the concrete. (hire a pro to cut these or rent a concrete saw and do it yourself. It must be done correctly. Break those cut blocks out and dispose of them. Next, with shovels, dig out 6 to 8 inches from the edges of your 48in X 48in block outs. 6 inches deep will be deep enough. Optional: put 4 rods, 8 inches long, into each edge of those holes (16 altogether) near the bottom edge of the old floor. This will tie the new and old floor together.
This repair produces mushroom shaped ingots to anchor bolt your lift into. Use a ready mix concrete supplier, order 3500 psi concrete material. Finish the concrete very smooth, it’s now ready for anything.
Overhead clearance
Two post lifts are built in two configurations. Most popular is closed top, commonly known as “clear floor”. They have a structural piece known as a cross bar on top, that ties left to right columns together. Hoses and cables run through it. For each side.
The other configuration is known as an “open top”. These have a plate or cover over the cables and hoses running left to right tying those sides together. That plate is attached to the floor. These open top lifts make up 20% of what is sold usually because of low ceilings or truck work.
Closed top, clear floor, types require 12 feet clearance under rafters or ceilings. Actually, they need a few inches more than the lift structure; because a human will need to reach in there to do install and service during the life of the lift. Some of these lifts are sold with extended tops. Usually two extra feet, for special installations where extra tall vehicles are serviced. All lifts rise 72 inches. You can purchase a lift that raises an extra 6 inches if you need such a specification.
Open top lifts are fine for all service work. The floor plates are not a problem, you get used to it in a few hours. They often cost less and you will never have damages to an extended roof vehicle or a ladder rack on a truck.
If you have rafters in the way
There are ways to circumvent overhead clearance troubles.
Ceilings: Check to see if there is space above your ceiling to build a box that the top of the cars will
fit into. Something like 8ft wide by 10ft long will likely work fine. You can finish the box with drywall making it blend well with a finished room. You may need a contractor for these modifications to structures. Don’t take chances!
Open rafters are a bit easier, no less structurally critical. First, if you are doing a new build, specify
scissors trusses, above the lift. Scissors trusses will give you plenty of room to allow full rise of your lift with no danger of hitting vehicles’ roofs overhead.
Sometimes open rafters can be modified, scissors style, to allow a box like area to allow vehicles to protrude above the normal level of the bottom of your rafters. Be very smart when considering this modification. It works just dandy, but it must be done properly or your roof could cave in. Hire a professional to do this. There is NO maybe and No room for error.
The last way to deal with rafters that are too low is even more simple. IF your rafters run across your roof, in the same direction, left to right as your lift will lay left to right it’s simple. Install the lift so that the top fits up into and between the rafters. Getting the columns upright can be a challenge but it is done, somewhere, every day.
When purchasing a lift, always consider the height, from the frame to the top of the vehicles you lift, add six feet for the lift stroke or rise. That is how you determine open top, closed top or extra extended top lifts.
