Leveling concrete floor of garage

Hi there LJ!
First post. Recently started renting a garage/shed space in Sf that I m making my woodshop.

Thanks,
John

- jovol

Better check with the person you are renting from first.

-- Handcrafted by Mike Henderson - Channelview, Texas

Welcome to Ljs John
It’s pretty unusual for a renter to go to the expense to level a floor for the owner. There are a number of ways #1
buy some self-leveling concrete and read the instructions how to use it #2 use sleepers( strips of wood that are cut at an angle to counter the slant) and then apply sheet goods over the top of the sleepers,#3 hire a company that has a diamond grinder and have them grind it level.

-- https://www.artisticwoodstudio.com/videos

There’s supposed to be a slope for drainage.

And a belated welcome to Lumber Jocks Jovol!

Hi there LJ!
First post. Recently started renting a garage/shed space in Sf that I m making my woodshop.

Thanks,
John

- jovol

Better check with the person you are renting from first.

- MT_Stringer

I’ve asked my landlord and she is okay with me doing so. This is an outdoor shed/garage in well-used condition, and she is open to any rehabilitations I do. Unfortunately supply of such spaces is on the low side in SF.

Welcome to Ljs John
It s pretty unusual for a renter to go to the expense to level a floor for the owner. There are a number of ways #1
buy some self-leveling concrete and read the instructions how to use it #2 use sleepers( strips of wood that are cut at an angle to counter the slant) and then apply sheet goods over the top of the sleepers,#3 hire a company that has a diamond grinder and have them grind it level.

- a1Jim

The self-leveling route sounds doable and robust. How thick can a layer of this go? The difference in the low-side to the high-side is about four inches. With all my recent woodworking tool purchases, it would be nice to use them for this process. The only part of the wooden floor fix I’m worried about is the height delta between the floor and outside, making it hard to wheel machines in.

There s supposed to be a slope for drainage.

- waho6o9

That’s a valid point. There likely should be some sort of mild slope. However, the current floor is very uneven and “warped” (presumably sunken over the years). However, I don’t think a drastic slope for a shed that shouldn’t be draining anything is intentional.

The only part of the wooden floor fix I m worried about is the height delta between the floor and outside, making it hard to wheel machines in.

Is there room outside the door to install a ramp that will solve that problem? Seems like no matter which method you use, that end of the shop is going to be 4” higher than it is now. :-0

-- My mother said that anyone learning to cook needed a large dog to eat the mistakes. As a sculptor of wood I have always tried to keep a fireplace. (Norman Ridenour)

Good point. There is room I could add a ramp. The sleeper+plywood floor does seem the least invasive and probably cheapest route! Not to mention I could take the materials with me whenever I leave this space.

Is there special plywood to use for flooring? And what should be the thickness be?

I don’t think a thin layer of concrete will stand up to rolling machines.
It would have to be at least 2” thick, IMO.

I totally agree with Jim re: plywood.

I would definitely use 3/4 and I would check into the tongue and groove ply made for subflooring.
We have a product around here that is a waterproof strand board that is excellent and quite reasonable cost.

Good luck I think it will be a worthwhile investment and make the shop much better to work in.

-- Everything is a prototype thats why its one of a kind!!

Something like this?
T&G Oriented Strand Board 8’ x 4’ x 23/32”
http://www.homedepot.com/p/Unbranded-T-G-Oriented-Strand-Board-Common-23-32-in-x-4-ft-x-8-ft-Actual-0-703-in-x-47-75-in-x-95-75-in-920924/100054132
... this is actually way cheaper than I expected.

Would this be fine without any other layer atop it?

I would be concerned about any plywood or especially strand board laying directly on concrete. I would use pressure treated sleepers to level floor first, then a subfloor made for moisture or even 5/4 pressure treated deck boards. Also ask yourself: How many critters and bugs are going to move in under this gap in the floor ? Maybe layer of self leveling concrete will solve a lot of future problems .
Check prices on product called DRI CORE. Comes in 2’x2’ panels, made to lay direct on concrete. Can be removed easily if something goes wrong in future (like flooding)
These are just my thoughts !

-- "My mission in life - make everyone smile !"

I had this problem and solved it by ripping 2×4’s to different widths to level the finished floor and screwed them together and screwed tongue and groove plywood over it. (Not anchored to the floor) When I moved I unscrewed all of this and took the floor with me, and installed it in my new shop. I knew where the heaviest equipment would be and put the ripped 2×4’s 12” on center there.

-- No PHD just a DD214 Lubbock Texas

You might want to look into sprays and/or powders for insect control. Put them down before you add the plywood floor.

-- "I love it when a plan comes together" John "Hannibal" Smith

This can turn into a pretty big and expensive project.

You can get self leveling products for floors, but they’re not meant to be the top coat. In the areas where it is not thick, it will eventually crack and come off the floor. They are meant to level the floor before putting in the final flooring, whether it be carpet, tile or hardwood.

You could also put the self leveling material down, then build a floating floor out of plywood with some 2×4 or similar support underneath so the plywood will not lay directly on the concrete.
I would stay away from the OSB. It will work under carpet or something like that but will not stand up very well to machinery rolling around or will also separate or swell with water spills or leaking from rain.

If you’re wanting to just fill holes, you can try some concrete and mix in some concrete adhesive and apply the adhesive to the floor also. We have done it in a shop we have here but it only is good for some of the deeper holes. If it’s shallow, it won’t stand up to too much rolling around on it.

Most self leveling products like K-15 Ardex have limitations on how thick they can be applied. Also, how high a lift (single poor) can be done at a time. I believe that an aggregate will be required for anything over an inch. Self leveling products are very expensive and tempermental when it comes to application.

If you are going to do this with a cementitious product, look into using a product like Paragon Deck Mud to do the actual slope correction. Basically it is a sand and Portland cement mixture that will give you about 1” over 10 sqft for less than $5. A self leveling pour can be applied over the top of that.

-- Paul, Duvall, WA

Sometimes, I get lazy, and this would be one of those times! Instead of all the work required to level/flatten the floor, I would get a quote or two from a concrete guy to pour a floor with some reinforced steel in it.

This would be a simple job for someone who does it for a living, and they have the tools and skills to do the job right the first time.

I don’t know if a permit would be required, but you could ask someone that knows.

-- Handcrafted by Mike Henderson - Channelview, Texas

A lot of concrete floors cracked because the dirt underneath them was not compacted properly, this could
cause problems with any floor poured over the top of the old floor, as MT_Stringer suggested above, you
should ask an expert that knows more about concrete floors than us. It might cost you, but maybe not as
much as having to redo a mistake.

-- As ever, Gus-the 80 yr young apprentice carpenter