Bill Ball

Will cracks appear before or during the car falling off the rack? I don't mean to be facetious. So, you expect there to be some small "warning" cracks sufficiently before the fasteners start pulling out. I don't know. Just asking.

dr bob

If you don't have cracks within a couple feet of the anchors you are probably OK. From the picture, I see cracks in the foreground and what look like related cracking leading back towards the column on the left. That would warrant more careful inspection, at least for me.

The failure mode of the anchors in the concrete is a cone-shaped withdrawal section under each anchor. In the thinner concrete, the top diameter might be as much as 6", as little as a couple inches depending on the strength of the concrete. Obviously all the anchors need to fail at the same time. So all will fail at the same time. No 'warning cracks', creaking or other noises that might give you enough warning to get clear before the inevitable gravity drops the car towards the first-fail side. Not good.

Kevin in Atlanta

When I sited the jacks for placement in the garage the left one was within 6 inches of a foundation crack. I then moved them back about 15-18 inches closer to the garage entrance. Now there is at least 2 feet of distance that crack. No other cracks are nearby. The left jack has two holes with the 5-6 inch depth - these are the 2 farthest away from the garage door. The other three had 3 plus inches of foundation and were the ones I used a two part cement epoxy. And also, the jacks needed no leveling or other adjustment. They are perfectly plumb. FWIW, the garage dates back to '75.

curtisr

For the Canadian GTA guys, you might wish to consider a ProPark 8 as an alternative.

When you call for better pricing they'll knock a $100 off.

Of course, you'll have to go to Vaughan and pick it up so that'll add a some $$$ to the final price. It also helps to have a shop crane handy to unload it--the heaviest piece is 700 pounds.

http://www.directlift.ca/pro-park-8.htm

MGW-Fla

Ok, here's the solution I am going with. My GC friend had his PE friend come by & take a look at my garage & floor, lift & specs, anchors & specs, etc. He agreed due to my garage floor having typically 3 1/2" slab thickness, either steel plates 2'x2'x.5", or cutting & pouring footer pads would be well advised. Steel plates were out as an option since a search found no steel supplier with smaller scrap pieces that we could purchase. So a full sheet of steel would be required to be purchased at about $1500 & the plates would still have to be cut & tapped.

We decided to use Sakrete with a 5000 psi strength since it was only a $1 a bag more than the standard Sakrete. The PE said concrete pads 3'x3'x2' depth would be more than adequate. My concern was the potential height of the water table beneath the concrete & whether I'd have the luxury of going 2' down & still stay dry enough. So he said we could make the pads wider & shallower at 4'x4'x1' depth with more than enough strength. Wide at 4'x4', but the 1' depth I felt would work without risk of any water potential. The GC works with a concrete contractor who said some of his guys might be willing to work with me on the weekends. One came by to give us his ideas & estimate last week & we all said "Lets get this going!"

I bought some Visqueen & taped off my garage to limit the dust clean up. The GC & I got the two areas to cut marked off for them. This morning they came & cut the concrete, then used a small jack hammer to bust up & out the concrete. With the concrete removed, there was yellow dirt beneath, a good start. They dug down & removed 1' of depth & it was all yellow dirt, very slightly damp, but not wet. All agreed it looked perfect, & it was very compacted.

The PE said to put 1'x1/2" rebar 4" into the sides of the cut concrete, leaving 8" in the new area to be poured. This to tie the footer pads to the existing slab. He said two per side, we opted for three. He also said to put 4'x1/2" rebar 3-4" off the bottom of the hole, tied together as a grid, with three each direction. After this was all accomplished for both holes, they had to stop for the day.

Each excavated area is 32 cu ft; We rounded up to 40 cu ft just in case. The 80 lb bags of Sakcrete are rated to do .6 cu ft. That worked out to 67 bags & we rounded up to 70. I went & purchased the Sakrete & they are to pick it up on their way over tomorrow morning to pour the new pads. The Sakrete is supposed to require 28 days to fully cure prior to drilling for the anchors.

Here are some pics of the footer holes after they were dug, with the rebar going in; and after completed awaiting concrete. I'll take some more tomorrow as the concrete goes in.

DKWalser

Very nice. That should address the concerns raised.

It's been a long time since I set concrete forms & rebar, but I'm surprised that the rebar that were drilled into the existing concrete have not been tied into your new grid. I think we always tied the bar that was drilled into the footings (or other existing concrete) into the new field of rebar. I seem to recall cutting a bunch of short pieces of bar to drop down from the drilled-in rods to the grid.

Of course, standards could have changed since I occasionally helped with such projects more than 3 decades ago. Besides, I was just a grunt working construction to pay for my education, so I never pretended to understand what the standards were. IIRC, the job I was working on was an irrigation diversion dam. The standards were likely much different than would apply to your pour. So, don't read anything into my my surprise other than a raised eyebrow. I'm just mildly curious as to why they omitted that step.

dr bob

Did you use epoxy to anchor the rebar stubs in the old concrete? Pretty important to anchor them that way or risk cracking there. Otherwise it looks like the right way to go.

Edsel Murphy, the patron saint of projects like this, guarantees that your anchors/imbeds for the lift column will end up right where the rebar is sitting. Do a little tape-measure work and adjust the rebar position if needed to avoid the interference. Otherwise you'll be hunting down a 7/8" rebar cutter bit to go through the steel. The carbide-tipped bit for the concrete will get trashed quickly trying to go through the steel. More importantly, it will drift sideways in the hole, enlarging it to the point the cinch ring on the anchor won't set correctly.


Looking very good!


For others-- There are several extended threads on MaxJax lift installation on Garagejournal.com Worth browsing if you have issues or concerns.

MGW-Fla

The GC wondered about epoxying the 12" rebar into the existing slab & the PE said not necessary. With the 4'x4'x12" footer with 5000lb psi, he said the tie in should never be an issue. And the PE has 3+ decades of home/commercial PE work & partners in a company. We did add a 3rd 12" rebar on each side instead of the two he said was needed. Regarding the hitting of the rebar when we drill for the lift anchors, that shouldn't be an issue. The lift will be in the middle of the 4'x4' pad; the 12" rebar near the surface is on the sides of the pad only 8" in from the edge; and the grid of rebar is 8-9" from the surface(3-4" from the bottom). I'm gonna use the 5 1/4" Wejit epoxy anchors I got from GES instead of the smaller tension anchors they supply with the lift. But we did discuss that issue.

They are finished now & I am happy with it; The main concrete guy is coming back later today to finish trowel the surface & to make sure its complete. Used 52 of the 80lb bags of Sakrete, so I'll return the remaining 18. I'll post some of the pics from today a little later. Started to etch the nick names of our current 928 & 968, and our former '91 928 into one of the pads for posterity, but decided to forgo instead.

MGW-Fla

Here are a few pics from today. From ready to mix/pour, to pouring, to finished product. Can't wait till its ready to drill for the anchors! I can now finally see the light at the end of a very long tunnel! Woooooo Hoooooo!