Suggestions for pit cover/support?

[slipnfall]

Hi Folks,

I have a detached 1.5 car garage with a concrete slab, and built-in car pit. It's a great feature, but due to the layout of my garage (pillars and such), it makes positioning jacks/jack stands around it difficult. It supports a single tire from a 1/2ton pickup fine, but I do more than just park in my garage.

I'm unsure on the dimensions off-hand (will get them shortly) - maybe 5' wide, ~8' long. The walls of the pit are cinder-block, with the concrete recessed to create a 'lip' just deept enough for 2x6's. Current there that's what's covering the pit.

I'm looking for some ideas on replacing one or two of the 2x6's so I can reliably place a jack or stands over the pit. I was thinking either some sort of tube steel or maybe even lagging some 2x6's together. Obviously it would take 2-3 of these to fit a jack onto.

Any thoughts? I'm unsure of the structural needs to support such weight over that span. I'd rather them not weight 1000lbs, but don't want something unsafe either.

Ideas?

Thanks! Great forum BTW.

 

[vettebrett]

ANy pictures, that would help alot.

 

[GeorgiaHybrid]

A W6x15 A992 beam is 6" deep with a 6" flange. It will hold 40,000 lbs plus if uniformly loaded. For use as a jack support I would put 1/4x2 1/2 stiffeners in the web at 12" C/C welded with 3/16 fillet weld on both side top and bottom and the same weld except make them 2 welds, 2" long each in the web.

A jacking load is a concentrated load instead of uniform and the deflection amount in the beam will depend on the location. By using the stiffeners as above, the beam should be more than adequate to carry the load unless you are jacking up an Abrams tank. If you need additional width, use two of them.

A 5-foot section would weigh 75 pounds plus another 10 pounds or so for the stiffeners and weld. The big question here is the “lip” on the pit. Are they just plain CMU block without any fill? How wide is the lip?

 

[WNYflyer]

May want to try using (2) 6" channels C6x8.2, C6x10.5 etc facing back to back with a decent gap between them. Then put a plate over the top that is of sufficient thickness to distribute the load to both channels while being wide enough to accept the base of your stands or jack. You could clamp this plate in place by placing another plate on the bottom of the channels and through bolting (countersunk ?) the top and bottom plate together (no holes in channels)to tie/clamp everything to the channels. Gives you a lot of flexibility in placement of the plate while minimizing the weight of the pieces you need to handle. A single C6x8.2 spanning say 6' can carry a single point load of about 4400# placed at its center span with minimal deflection this is assuming the C6's top flange is not restrained from moving laterally by floor plate/sheeting etc. which is a conservative assumption. Not a final design but in the ball park and an idea.

As GeorgiaHybrid said you need to be concerned with what the beam/channel/tube is bearing on at the ends. Typically you would want grout/concrete filled block vertical block cores where the beams bear.

Hope this helps.

 

[kwb]

Floor Grating is the right answer.

Here in the NW we have a place called Grating Pacific I have used for work and they have lots of offerings and I would expect that there is a similar suppilier locally to the OP.

You can get in welded steel, some stamped steel options, and even FRP options.

We had grates in paint booth floor that we frequently would have a car on jackstands on when I worked in body shop.

You will end up with a few pieces that are easy to lift when you want to get into the pit.

 

[Mr_fixit]

I had a pit purt in my first garage. It was only about 3' wide. 5' sounds pretty wide. I used 3" b y about 8" pieces of rough cut oak that would support anything I could drive on it. I left the lumber on except when I was working on cars. Then I would remove some or all pieces depending on where I need to gert access.


If yours is really 5' wide, you're going to need some type of steel I beams to jack against.

 

[GeorgiaHybrid]

kwb,

The only way that grating will work is to support it with steel beams or channels. A W4x13 beam sitting on a 1/2 thick embeded plate would leave space for some 1 1/2 type WB grating. I can check the span tables tomorrow but I'm fairly sure that it will only span 2 feet or less with the loading that a car can put on it. That is assuming something in the range of 1 1/2x1/4 bearing bars @ 1 3/16 C/C and cross bars @ 4"C/C. There is not any grating readily available that can span 5 feet. Custom grating yes, but that would cost more than the beams.

 

[slipnfall]

First off, THANKS for all the replies! I was expecting to get an email notification, but I guess I didn't have them turned on.

Now that there is some interest, I'll be sure to get some picture and dimensions.

The steel grating that I've been exposed to is *heavy*: plus it would make rolling a jack over and positioning a jack stand difficult without a smooth sheet of steel over top.

I should have added that the beams must lay flush with the floor (~1.5" thick) to avoid trip hazzards and to easily roll the jack over the existing 2x6's (I don't intend to replace them all). Something between 5.5-16.5" wide would be preferred. Am I asking for too much?? There's a local steel supplier I've been meaning to visit that sells lots of scrap, so I'm sure they would have something there... just want to be sure I know what I'm asking for.

Cheers,
Jamie

 

[kwb]

kwb,

The only way that grating will work is to support it with steel beams or channels. A W4x13 beam sitting on a 1/2 thick embeded plate would leave space for some 1 1/2 type WB grating. I can check the span tables tomorrow but I'm fairly sure that it will only span 2 feet or less with the loading that a car can put on it. That is assuming something in the range of 1 1/2x1/4 bearing bars @ 1 3/16 C/C and cross bars @ 4"C/C. There is not any grating readily available that can span 5 feet. Custom grating yes, but that would cost more than the beams.

I looked at the grating book I have at my desk at work today and it looked like they had standard panels in 1.5" thickness that would work for normal pass car loading on a 5' span.

Agreed that a beam in the center would be easy and allow for much higher loads than grating could span alone but it also adds complexity to being able to use the pit.

 

[slipnfall]

OK here's the scoop - pit is indeed only 3' wide (you would think I'm never in it, HA!) wall-to-wall. Roughly 7.5' long. The LIP, is 1.5" high, and 3.5" wide all the way around.

The concrete slab appears to be poured all the way down to the first block, with perhaps a solid cap on top the block (the concrete was obviously trowled over this area, so it's either that, OR solid slab down this far). Unsure if block is hollow or poured.

Hope this helps some - pictures are below, but I didn't grab my keys to move the truck out of the way for better shots.

Thanks!!!
Jamie

This side has a few blocks removed for a shelf area - looks to be a solid concrete 'header' over top:

 

[c39er]

My pit is 3' wide by 12' long. I have 1-1/2" tall heavy grating-don't know the specs of it. I drive over it with old heavy 40's cars all the time -never deflects/bends. Don't know that I'd jack a heavy car up over it though. Works well for me.

 

[tbob]

I want to add a pit to my garage. My floor was poured with a section blocked off. How deep is your pit and do you have a drain in the floor? I was thinking of putting a barrel(w/ holes) flled with gravel under mine

Thanks, Terry

 

[GeorgiaHybrid]

slipnfall,

With a type WB grating, 1 1/2x3/16 bearing bars @ 1 3/16 C/C and cross bars at either 2" or 4" C/C, the maximum uniform load is just over 1,000 lbs/sq ft. A concentrated load at mid span is good for 1,500 pounds.

If you go with type WD grating (bearing bars @ 15/16 C/C) the loading can be increased to 1250 lbs/sq ft for a uniform load and 1,900 pounds for a concentrated load.

As always, check with the grating supplier to verify the load capacity. With a 1 1/2 tall lip, grating is the only way you can anywhere close to what you require.

 

[slipnfall]

I want to add a pit to my garage. My floor was poured with a section blocked off. How deep is your pit and do you have a drain in the floor? I was thinking of putting a barrel(w/ holes) flled with gravel under mine Thanks, Terry

Hi Terry,

If I had to venture a guess, it's about 5.5' deep. The bottom is entirely gravel, unsure on depth. I just add/remove gravel to suit the height, and the entire floor is a 'drain' (ha!) Of course I don't drain fluids purposfully here, but if a little oil or coolant drips down, I don't really worry with it. I highly doubt my grandfather (who built the garage) had this in mind, rather a cheap way out.

From my understanding the garage is also built atop a 'french drain' - there was a toilet stall, but it's since been ripped out to house my upright 60gal.