adding a pit help/ ideas

[rdsk8ter]

I did a search but I cannot find a good link to help my situation. I have an existing garage that I don't think I can easily re frame the rafters into being roomy for a lift (double cantilever truss system that runs side to side). What I am wondering is it hard to add a pit obviously its hard work but I do have a couple questions
1) Do I need to have and engineer design the walls or just build it like a retaining wall with rebar and cinder blocks filled.
2) Could I cut the middle of an existing slab dig down and build walls.
3) I would like to be able to stand in the pit so I'm thinking 5' deep or so would be good but what is the average height and length for a pit?
4) Im thinking folding guide rails to help prevent fall ins. Also would the top being 1/4" angle and flat plate be strong enough to drive on when closed Im not opposed to running gussets but don't want to use a engine lift to take them out of place
Has anyone here cut in a pit also I will vent the pit with an intake and exhaust fans run under the slab I'm thinking air and electrical would be good too. I am just in the dreaming stages but is there a good writeup somewhere?
Am I overlooking anything here?

 

[Aberdale]

Check to see where your water table is, and what the slope and drainage is outside the garage. If the water table is below your proposed pit floor, you are good to go. If the water table is shallow, you will need to include a sump pump and drain. And it will run a lot.

I quit using my pit 10 years ago. It is currently covered and has 12" of water in it because I got tired of the musty dampness, and got tired of the sump pump running up my electric bill.

I ended up building a new shop with 14' ceilings and installed a lift. At some point I will be filling my pit back in.

'dale

 

[bad_idea]

They stopped putting pits in a garage for a reason. Ventilation being one reason, dropping cars in it another reason, and the EPA being the final nail in the coffin.

 

[premierplayer]

and all the quick change places use them

 

[HOTFR8]

I put a pit in recently. You can get a look at it in my topic about the extensions. Sheddwellers.

Venting is very essential as it waterproofing. With your electrical wiring in the pit you should also consider it being spark resistant. If the pit is not in use a good solid covering that you can walk and drive on.

 

[Stuart in MN]

and all the quick change places use them

Oil change places don't really have pits - they have an entire lower level of the building, basically a basement with an opening in the floor above to access the bottom of the cars.

Since they're commercial buildings they have to meet NEC regulations, as the lower level is considered a hazardous area. They have separate stairways for egress, and proper ventilation and electrical wiring methods in order to deal with exhaust fumes and flammable vapors that may be present.

The NEC doesn't have any restrictions for pits in residential garages, but there may be other parts of the national fire code that prohibit them - while I haven't found any, I haven't researched it very much. Also, there may be local or state regulations, but you'll have to research that for your specific location.

The main issues are health and safety. There's the potential for dangerous or flammable fumes or vapors, and you need to be able to get out quickly - for instance, if there was a fire you wouldn't want to be trapped down there. Convenience is also an issue, as mentioned above they can be inconvenient and you may end up with a big hole in the floor you never use.

 

[bczygan]

There is no reason you can't re-frame or even raise the roof as needed.

Give us inside and outside photos and dimensions.

 

[ptschram]

I go into shops everyday that have pits anywhere from four feet deep to five or six feet deep. None of them have any ventilation either-which does concern me-bt they do have sealed lighting.

I can't wait for next spring as I will then be able to add a pit to the dead bay in my shop, next to the four-post lift. I will provide a means for ventilation as I recognize the risk.

 

[HOTFR8]

One other thing, build it so when you stand in it the floor is about your eye level.

 

[Sureshot]

I recently talked to a lift tech and installer in South Dakota and he told me lots of places were removing lifts and putting in pits.

 

[MichaelWest]

Aside from the many issues of safety, structure, etc., I have an old book on building shops that discusses it as a solution. It says to build it 30 by 60 inches with a 2 by 2 foot drain of crushed gravel at bottom. I assume you adjust depth to your height. I recall an old service station garage that had stairs so if you could get in you could get out, like the outside entry to a basement or cellar.

I think a lift is better if you have height, but I have 100-inch ceilings so it is always a thought, even with a low style lift. I consider it a lot.

 

[rdsk8ter]

I would have external venting an intake fan at one end and an exhaust vent so it pulls the air across the length. I would also run vapor proof lights to be safe. I didn't think about the water level as I don't want a sump they are irritating. Hotfr8 could you link that pit for me I can't find it. As for stairs I was thinking an access ladder but I bet the stairs would be nice.

 

[justanengineer]

I go into shops everyday that have pits anywhere from four feet deep to five or six feet deep. None of them have any ventilation either-which does concern me-bt they do have sealed lighting.

I believe the sealed lighting is simply due to potential spills and the ventilation concern is a bit overplayed. I worked in pits daily in the military and we also had the OSHA inspector walk through almost weekly, but he never said a word about a lack of ventilation. Proper vehicle chocking, crane inspection/training, and everything else imaginable - yes regularly, ventilation no, not even in our welding pit.

Personally, I love pits for speed and safety. Pull the vehicle in and try to pull the covers. If they dont move, youre parked on them. Theres no way the vehicle can fall and no time wasted ******* around with a lift.

 

[HotrodHR]

I plan on eventually putting a pit in my wife's garage (it's attached)... It'll be steel with a sliding door and seating for six... Tornado shelter!!!

My shop on the other hand has room for a lift just waiting on PO approval from my CFO!

 

[c39er]

I have 3 lifts and a pit I built 20 years ago. It's ventilated powered up and has a excellent drainage system as the water table is three feet higher than the bottom floor. Always dry as can be even here in the wet NW.
I don't really use it much except with my big truck.

 

[ed_h]

I put a pit in my garage. I dug it by hand before the floor was poured. It looks a lot like the pics in c39er's post--about the same dimensions, same rebar step rungs. I have recesses in the two long walls for electric and air receptacles. There is a 3 x 3 x 1/2 angle lip around it and I put 3-inch bridge planks across it that are strong enough to drive on.

I couldn't really put in a proper drain, so there is a "French Drain" under it--a grate in the floor that leads to a perforated five gallon bucket full of crushed rock.

I also put 3-inch ducts in that come out near the floor for ventilation.

 

[Sureshot]

Very nice setup c39er. I would put steps myself but that is nice.

 

[c39er]

Very nice setup c39er. I would put steps myself but that is nice.

If I were to do it again-yes steps would be installed.

 

[kbs2244]

After you put it in be sure to put a hoist over it.
They make a great storage place for those big clumsy things that you have to have but rarely use.

 

[gungatim]

all the quick oil change places I worked in as a teen except one had pits. most were converted old gas stations where the old in ground hoists were. no ventilation, no drainage. they were generally 7 ft deep or so, and had a wood or expanded metal floor to stand on with oil dry underneath. We worked 10 hrs a day and would maybe change 50 or 60 cars oil during a shift. cars running all the time and never had an issue with venthilation, although we went up and down after every car.

I also helped put in a pit in my FIL's barn. it is a good 6 ft. dep and 42" wide. ladder at one end and stairs at the other. again, no venthilation. water table was about 48", so we dug lower and put in a pump to keep the water out while we finished digging, then built a "bathtub" form to pur cement around, essentially floor and walls are all one piece. never had a drop of water. We ran a pipe into it so we could run air lines and electric, with a recessed shelf along one side to set oil filters and tools. if you are concerned about venthilation, put in a fan...

 

[1/2 Cup]

We have both hoists and pits at my work, the pits are used daily. Our Health and Safety procedures in the workshop are audited by Standards Australia on an annual basis. There are safe work procedures in place for all our operations in the shop including work in the pits
They have natural ventilation, and we also have a high ground water table and have no problems with seepage at all. The only issue we have is that the odd snake likes to call it home.
That said in both cases there are two points of access and egress and are not considered a confined space under the code.

 

[rdsk8ter]

Ok I think I am leaning toward the pit a bit stronger now but could use some help. How if I cut my current floor would it be best way to tie in the new concrete walls to the floor. Obviously a rebar frame but are there any good spots to read on the design process. I have figured that I can create about a 6-8 air exchange rate with some venting witch will prevent fumes from building up. Also the pit could double for storage of the engine lift and the stand etc. Ill be putting a small lift above to lift stuff out. Thank for all the help.

 

[HOTFR8]

Is it a concrete floor ? If so just cut using a concrete saw and if so cut it a bit wider and bigger so you have room to dig and build it in.

Mine was made and bricked up before we did the concrete floor.

 

[sberry]

I wouldn't want one, would fix the building first.

 

[rdsk8ter]

The costs associated with raising the roof are crazy high. I'm not really worried about fall in danger or gas build up as when its closed I should be able to have a football team line dancing on it. Pulling cars in will only be with the doors closed then I will slide them out from an access panel. I guess the biggest part is even though I will hire the concrete out I like to have a good idea on how it should be done so I know the contractor knows their stuff. I was thinking 4" thick walls but can't find a writeup on it or would filled blocks be better. I'm going to try to call the city today to fine the water table heights but that's nor a huge deal. As far as running air and electricity I'm thinking a couple lights and a 4plex outlet, air I will more then likely just run a flex line down a PVC and replace it as needed leaving around 30' in the pit. As far as means of escape what's the thoughts on a ladder on one side and a short staircase on the other? Trying to put stairs on both sides won't be as easy as it sounds.

 

[c39er]

After you put it in be sure to put a hoist over it.
They make a great storage place for those big clumsy things that you have to have but rarely use.

I took your advice.

 

[G_P]

I assume you make the pit longer than the vehicles you plan on servicing? So you can get in/out while the car is over the pit?

 

[ed_h]

For mine, I used 8" concrete blocks, with every third core filled with concrete with #4 rebar, and ladder reinforcement every other course. With that construction, you probably wouldn't have to tie it to the floor. I can't think of a good and easy way to tie the new walls to an existing floor.

For access, I have bent rebar rungs on both ends. My pit is only about 10 feet long, so I park the vehicle over the pit so that one end is open.

 

[Lippyp]

Over here you can buy prefabricated drop in fibreglass pits. Totally waterproof and they come prewired for lighting and power, dig a hole, drop liner in, backfill around with sand jobs a good 'un.

 

[BuickFarmer]

I wouldn't want one, would fix the building first.

what he said.

you'll get tired of climbing in and out for forgotten tools I gawarantee. the older you get the more you'll appreciate what I'm saying.

 

[sberry]

I am not sure what a guy would use if for other than an oil change on a modern car?.

 

[c39er]

I am not sure what a guy would use if for other than an oil change on a modern car?.

Cooling off in the heat of summer.

 

[rdsk8ter]

Honestly in thinking more for the storage then the working at this point oil changes and exhaust work will be the best from down there. Any links on the pits that are performed that has peaked my interest.

 

[HOTFR8]

Honestly in thinking more for the storage then the working at this point oil changes and exhaust work will be the best from down there. Any links on the pits that are performed that has peaked my interest.

Did you look at mine ? Link below the Sheddwellers, my shed extensions.

 

[Dragfluid]

This has been an interesting thread. Having been in the auto repair trade for 39 years, I have some input.
What repair operations do you hope to achieve with a pit? Changing oil, of course. Transmission fluid changes, too. If you have a rear wheel drive, u-joints. But not a lot else. Someone mentioned exhaust, but you're going to be cramped, depending on the system/vehicle. Removing a RWD transmission or transfer case will require a transmission jack. Not a lot of room down there for one of those, plus how to get the unit out of the pit once it's pulled? Not even the simple things like pulling a tire off can be done.
And yes, the issue of vapors settling in the pit is indeed a real one. Carbon dioxide builds up in your system and never gets lower. Until one day, your body has had enough.
Not trying to be negative here, just want to be sure that you're realistic in your expectations. The price of lifts have come down quite a bit over the years. And they all work fine. I would take a serious look at extending the studs in your current building.

 

[c39er]

A pit was a fun challenge for me to build! Highly recommend it.

 

[rdsk8ter]

Did you look at mine ? Link below the Sheddwellers, my shed extensions.

actually your build is what got me thinking hahaha I couldnt find it again

 

[volvo]

..
Your FIRST call should be to your insurance company to be sure that they will insure you with a pit! Most will not.

 

[c39er]

No insurance company will insure anything with any slight risk now days.

 

[rdsk8ter]

Yea with half of my state flooding I dont want to even give it a chance. They never asked if there was one there. I do have access to different gas detectors and I have a nifty idea to have them kick on as needed to avoid buildup of any odors, or vapors. Again I am still in the thinking stage I dont know If this will come to be but the "idea" has got me intrigued enough to do alot of research on the subject. Yes I am that guy I actually like to learn but only what peaks my mind.