Waterproofing a garage workpit

JMSE

I'm set on building a shed in the back garden complete with a car workpit. Don't anyone try to tell me I will fall into the hole someday or that I will pass out someday on the fumes and heavy gases wafting around the bottom of it. Thats because I have the hole for said pit dug out and waiting for me to fix steel and shutter it and pour the concrete. My problem is the water table is about 4' higher than the floor of this pit so I need to waterproof it. So, the options are (I think) to put in a drainage area and sump below the concrete level and install a pump to keep the surrounding water table lower, or having googled intensively on this, to use a sodium bentonite product called Voltex to seal out water totally.

Being a man of modest means and not a builder, I'm winging it on this one. Does anyone have any advice on where a man can buy this stuff or is it the wrong way to go.

hobie

What ever else you do I would consider putting in a pond liner ....... put a layer of sand on the floor of the pit ..... some old carpet also, if you have it .... now pour a sub floor concrete base on top of the liner and after this sets, position shuttering and pour the concrete walls and finished base .......

I'm assuming you can do this without the water level rising while the work is being done? .... ...... if not you need to dig a sump hole close to the wall of the pit and a foot or so deeper than the hole ..... put in a submersible to keep the water out of the hole .... do the construction work and then the sump can be filled in after the concrete has set ....

post some photos when you have finished ....

ps. if you do a good job on the sump hole (line it with a plastic pipe?) ..... you could leave it in place (just in case!!!! )

galwaytt

first of all - you're mad !!:D I hope you have very, very good house insurance...........if you do have an accident in it/with it, you're on your own.

When I lived in Kingswood, in Bristol, in 1990, a young mechanic was killed in a pit fire, so I'm telling you now, you're asking for it......................

Anyhoo - the water. You should use Grace waterproofing products - I can't remember the name of it, but they used it on my new basement, recently - go to a builder's providers and ask about - Preprufe? I think it's called........

You're still mad, though..............:D

JMSE

A pond liner! havent come across that idea before, sounds like a real prospect. Had looked at all the other PVC membranes out there and none of them come in the size required and would involve seams (a non starter) but a large one-piece pond liner might just be what I need. I've just e'mailed a company in the UK 'Fawcett Pond Liners' to see what they recommend. Are they strong enough for use with concrete?


On the insurance point, yeah I know but isnt insurance the most inhibiting damn thing in the world, and if I can get away without it especially in my own back yard, then I'll be doing just that. Pit will be covered 99.9% of the time.

Mr.Diagnostic

JMSE wrote:

Don't anyone try to tell me I will fall into the hole someday or that I will pass out someday on the fumes and heavy gases wafting around the bottom of it.

I know you said not to, but, the safety aspect is worth a mention. You should consider an extractor fan and even a plumbed in fire system along with lighting. make sure you have easy access/escape at both ends. There is a good reason that a lot of pits have been filled in.
You would be surprised how cheaply you could buy a proper lift if you search, much safer and easier to work with.

the_syco

As above: make sure you have an easy exit, in case sh|t happens.

You plan for it not to happen, because if you don't plan, it may happen.

hobie

Some good points made above about safety ...... have to say I've never thought about them being dangerous ....

A buddie of mine has one (must be at least 20 years old) ..... steps both ends ..... I can't say I've ever heard him talk about fans, Fire Extinguishers etc but he does take great care to replace the wooden planks that slot into it when not in use ..... oh, and lighting is well provided for ...... Must mention the safety issues to him ..... :rolleyes:

re the question "Are they strong enough for use with concrete?" ..... Butyl Rubber liners are certainly strong enough ...... just make sure it can't come in contact with any sharp stones etc .....

galwaytt

Mr.Diagnostic wrote:

I know you said not to, but, the safety aspect is worth a mention. You should consider an extractor fan and even a plumbed in fire system along with lighting. make sure you have easy access/escape at both ends. There is a good reason that a lot of pits have been filled in.
You would be surprised how cheaply you could buy a proper lift if you search, much safer and easier to work with.

Dead right, forgive the pun.........:eek:

Beware though, if you're fitting a light and/or fan, that it'll need to be Atex compliant..........otherwise, when you switch on that light.........whoosh! :eek: Just cause your car is parked outside, doesn't mean it's safe - petrol fumes are heavier than air, and will slink along the ground, looking for a place to hide. Park the car outside.......and your pit can still fill with fumes.

Falling into it is the least of your problems then......

Finally, a pit isn't actually half as useful as you think - you can't work on hubs or suspensions...........exhausts, maybe, change oil...........mmmm, why is it you need one, again......?? A new lift, btw, is only 2k, and a used one a lot less.......

JohnBoy

you can get fiberglass insto pits, check out practical classics mag for ads, they are a single piece and while not cheap, take a lot of the work out of it.

iei044775

I used a chemical waterproofer for my basement - worked great. It's called Krayton and have a distributor in Ireland, it's just mixed with the Redimix before pouring, not too expensive either. Check this url.

http://www.kryton-ireland.com/

JMSE

Yep I am mad in fact I'm typing right now from my padded cell in the maddest nuthouse ever. But I'm still convinved I have a backyard outside the cell door and that theres a shed in it with a big hole.....

Anyway back to the other stuff, why I want it, at this stage I cant remember, all I know is a long time ago (bout a year) I dug this big hole in the back yard and now having spent 12 months staring down into it I sure as hell am not gonna just fill it back up again coz then I think they could probably come and take me away and I'd be the one who rang them. Sure the shed I build will more likely fall down on toppa me before I fall in the bloody pit. Handy for clutches, greasing uj's, CVs, gearboxs, drivetrain stuff, diff oil, engine oil, exhausts, big end stuff, havin the crack on a Wednesday night when you'd prefer to be standin under your wagon instead of lyin there! Cant be arsed with a lift coz I want to do a restoration job inside.

Sump hole is in place but I think I'll be filling it in afterwards, to leave it there would mean installing a drainage system to filter water down around the outside of the concrete and channeled over to the sump and thats something I dont want to add to the job. Like the butyl rubber pond liner idea although at only 1mm thick it seems light for the job.

Thanks for all the replies so far!