Building a wall for a car pit

AhhhHur

hello, im currently building a wall with 4” blocks then back filling with clay. Would you recommend to put the concrete blocks flat or would they be okay standing up? The pit is going to be around 1600mm deep. Also should i put a board and polythene behind the wall when back filling. Any help is appreciated thanks not a professional by any means ha

Dr.Tom

Built a pit years ago. Block on flat.

I also put in recessed areas both sides for strip lighting and as shelving.

AhhhHur

i think ill go with the flat blocks. Did you put anything behind the wall when filling to stop water or anything?

Cheers

Lumen

My biggest concern would be hydrostatic pressure. 1600mm is deep. Where's your water table at in winter?

Dr.Tom

https://www.boards.ie/discussion/comment/122448939#Comment_122448939

Zero waterproofing.

It let in water to a low level but not as bad as I thought it would.

Has since been filled and replaced with a 2 post lift.

whizbang

No way in hell I would get into that pit with the 4" block. They will not support the sides at that depth and with cars parked on it.

Dr_Colossus

I'd have gone with 9" cavity blocks with rebar re-enforcements vertically and horizontally tied together before infilling with concrete. Many years ago spent a summer building slatted house tanks, they were all made using large shuttering pans and mass concrete but there was significant steel work in situe first both in the floor and walls all tied together before anything was poured.

AhhhHur

If we build up the 4 inch block and then put a shutter up 4 inch off it and fill it with cement and rebar would it work ya reckon?

bfclancy2

block on flat, job done

AhhhHur

i want to just do that and make it somewhat waterproof itd make life a lot easier ha

The Continental Op

Dig a sump out in a corner that you can run a length of 6 inch drain pipe down to and if needed use it to pump out. Bottom of pipe would need some holes in it and back fill around the blockwork/concrete with something permeable like pea gravel.

LastFridayNight

the pit is outside is it? Yer mad if it is

AhhhHur

https://www.boards.ie/discussion/comment/122458734#Comment_122458734

building a concrete slab around it and building a shed.

https://www.boards.ie/discussion/comment/122458708#Comment_122458708

was thinking of running a drain pipe alright. Thanks for the suggestion ill look into the pea gravel cheers

scwazrh

https://www.boards.ie/discussion/2058362283/building-a-wall-for-a-car-pit

It will act as a sump without water proofing .But Blocks on flat ,heavy gauge polythene around the outside of the blocks and cori board up against the polythene to stop it getting pierced .Damp under concrete slab would be neeeded but bit late for that now.

AhhhHur

https://www.boards.ie/discussion/comment/122459162#Comment_122459162

would i have to take up the first layer of blocks or could i put blocks standing up beside them then start the blocks flat the whole way up? I put heavy gauge polythene under the slab in the pit hopefully it works lol

scwazrh

https://www.boards.ie/discussion/comment/122459266#Comment_122459266

On flat be better but you’ll get away with on edge for the first course.Polythene on floor needs to join with polythene for sides .You can use a water resist tape.Think of it as wrapping the complete build in a plastic bag ,any gaps and water will get through it.

AhhhHur

ill go a head with that thanks for the help. I may get a few extra blocks now🤣 thanks

Explosive_Cornflake

Here's a very comprehensive video series on a guy building a pit for farm machinery

stratowide

Built one of these maybe 25 years ago.Blocks on the flat and polythene underneath and at the sides.

Still leak proof and no cracks today.

Having been in many a pit over the years,the main problem you see is water ingress.

Put a sump in a corner with a mesh on top.

monseiur

It seems from photo that slab is too narrow, if, as it seems, the inside width is 36 inches with a 4 inch block - if you add another block to take block on flat you will end up with a pit 28 inches wide. Unless you're a midget that is much too narrow to operate in comfortably. The cheapest solution is to remove blocks make pit wider and pour a new wider slab over existing with steel reinforcement. Build walls with blocks on flat and finish off top with 9 inch steel reinforced concrete ring beam overhanging on both sides to suit width or car. Leave a 4 inch x 2 inch deep rebate in inside top of ring beam to take 9 inch x 2 inch planks to cover pit when not in use.

Also leave a duct for electric power (socket, lights etc) in pit, and steps to access, egress pit.

But before proceeding any further consider something like a 4 ton 2 post lift for €2,300.00. Just back fill pit and pour a suitable steel reinforced slab.

drury..

Get a lift

Do mechanics even fit pits these days

blackbox

I was thinking of making a pit but ended up buying a mid height lift.

Handier and safer and more useful - you can lift vehicle off its wheels.

GreeBo

Maybe I am mad, but water ingress is the least of my concerns with this pit.

At a minimum you need to add rebar and backfill behind the walls with concrete otherwise the whole thing is going to come in on top of you or somebody else, especially with a couple of ton of vehicle on top.

Watch this series for how it should be done.

https://www.youtube.com/watch?v=eneSiPSwMiU

The Continental Op

I'd also be worried about ventilation. One reason they aren't used that much anymore is that they are a health and safety nightmare. Run an engine near them and there is a potential for asphyxiating anyone using the pit, also any spilt volatile liquids tend to collect waiting for a source of ignition.

Thats without human stupidity. Friend in UK said his mate could put his Reliant Robin over the pit to do some work. The driver just rocked up wondered why he was being waved and shouted at and drove straight forward into the pit - an extreme example but it has happened.

dollylama

Put in a lift. A few hours in a pit and you'll know all about it... wet, cold feet, eyes full of crap and your back and neck stuck in an arched position