I'm trying to create a level, sturdy space outdoors, where I can ultimately set up a heavy workbench with various tools. This needs to be 2.5m wide, and 1.0-1.2m deep, giving sufficient area to both place the heavy workbench and to move around it on solid and steady footing. I can however only put up a temporary structure in the garden space.

Plan A has been to fill the area with self-levelling concrete at 10cm deep. This would make for a 500kg slab of concrete which, while level and sturdy, might need to be removed later.

Plan B is to use garden grids filled with gravel, on pre-tamped-and-levelled ground, or use prefab 1x1 foot slabs from the hardware store, fitting them together (though I don't like their bevelled edges as they will cause me to trip at some stage when I am focused on something more important and/or hazardous). I would then need to level across several of these "tiles", so hopefully a long spirit level would work. But Plan B means the surface is trivial enough to remove.

Having never levelled before: Is it likely I'll get a level surface just using unbonded garden grids or small concrete slabs, put together? I'd think their being individual would cause them to slowly settle in different ways, over time, even after serious initial tamping, thus creating an uneven surface.

  • Why are you asking for temporary solutions? If you would tell us what the constraints are that you are working with we'd be better able to help. I am very good with install of pavers, cmu walls. Just a bit more detail I think and we'd be able to understand more clearly. Thanks. And grins, what the heck is 'self leveling concrete'? Better hold the lime to keep the concrete more liquid, i guess. The forms dictate your floor/area level. Forms wouldn't hamper being able to haul the concrete away. Rebar and welded wire will not be able to be used as that makes concrete very tuf to remove.
    – stormy
    Jan 26, 2017 at 5:14

1 Answer 1


I am hearing that you have checked the regulations and want to push the boundaries and if you get caught be able to easily remove all your work.

First and foremost you NEVER want a level ground in the out of doors. You have to know where every drop of water that lands on your property will travel to. I AM an expert with grading and drainage. I taught that class in an accredited Landscape Architecture Program, University of Idaho.

What is the percentage of non-permeable surface you are allowed on your property? What slopes are you dealing with? How close to your home's foundation will you be augmenting?

Gravel is a wonderful surface, I kid you not. Crushed gravel, not pea gravel compacted is way cool but still has very little permeability. I got a feeling you've looked into this, excellent, but tell me how much permeability you've already used up and how much more you want to add. You can do this without permits but if your neighbors aren't great friends, they will turn you in for anything you do. Thus worrying about taking up concrete or pavers or slabs or even deck would explain your worries. There are a few ways around these rules but I'd have to know lots more information. Or I could give you options that would allow you to sleep at night.

The reason they do this is sort of obvious. Such as making perfectly level surfaces out of doors is just wrong. If your property doesn't allow for water to get back into the water table because you've got it all concreted or covered with impermeable surfaces, you are only allowing water to gather and gouge and run amok through your city or residential area. If everyone did what they wanted with their property we'd be in big trouble. Be nice if the city would educate WHY the rules are in place!

Here is the answer to a perfectly level out of doors workspace; The ground below the gravel is SLOPED. Above that the gravel is compacted to level and the 2 inches of sand is compacted to level...try to make at least a 1% slope for your pavers. I need to learn to draw on this internet. Using just words is tough. The area you need is not that big of a deal. Don't mess with grids all you need are the cmu concrete modular units in paver sizes (2X7X9 inches) with their plastic edging. Hard plastic you pound into the soil with huge spikes...not railroad spikes but this stuff holds your pavers in solidly. No spaces in between pavers! They should be 2 inches thick no thinner. This makes a CMU paver. 4" compacted gravel (5/8 minus at the most) with 2" mason sand compacted then laying your pavers using the edging. Wonderful surface. Just be aware, most municipalities have rules for impermeable surfaces.

I love concrete. But pavers are far far more superior! Look for 'Roman Cobble'. 4" of gravel, 2" of sand, make the subsoil with a slope, edge with 2X6 pressure treated lumber and you will LOVE this surface! Don't use any other color than dove gray with a small percentage of dark gray for your pavers. It is up to you but there is not another color for concrete pavers or walls or any structure in the garden that works as well as dove gray. Perhaps a bright blue painted something or other but you want your hardscape to blend in...all dove gray and the plants pop out like crazy. cmu pavers and walls and firepit and water feature

  • 1
    Well, "2.5m wide, and 1.0-1.2m deep" is only 3 sqm, that's 32.3 sq ft. You could fit five of them in a parking spot (9 ft by 18 ft). I wholly agree about the importance of drainage but the area to be surfaced is so small that it is unlikely to reach any of the critical thresholds unless the property is already dangerously near them.
    – Dan D.
    Jan 26, 2017 at 2:03
  • My point was to get you to look at the rules and covenants. Buildings and Code are very big sticklers for maintaining percentage of permeable surfaces. What makes sense and what is 'legal' are too often two separate entities. And it is impossible to know anything about your particular drainage system.
    – stormy
    Jan 26, 2017 at 5:06
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    1. Spot on, need to be able to quickly remove work in the (improbable) instance that such is requested. 2. Per regulations, I'm not in the USA. 3. This is a tiny fraction of a 30x10+ metre grass yard. 4. Drainage is very good, this whole area is river sand and the water table is about 70-80 cm down. There have to be torrential rains over weeks for water to actually reach the surface in the proposed location. As it is, we've been in drought conditions for some time. You really needn't worry about drainage here, it's a non-issue.
    – Engineer
    Jan 26, 2017 at 6:03
  • I love gravel. I'd form the area with pt 2X4 or wider to level this area. Stakes, SCREWS with enough depth for 4" of gravel. After installing the forms, I'd level your area with a shovel to keep a decent floor, add LANDSCAPE FABRIC on top of the subsoil. Then install your gravel. If you are able to get 3/8 minus versus 5/8 minus do it. Much easier on bare feet and wheel barrow wheels and it still allows percolation to a certain extent. Main thing is to use a rented compactor as you are installing your 4" of gravel. Seriously wonderful surface for what you are trying to do.
    – stormy
    Jan 26, 2017 at 20:10
  • I've come back to this as I'm looking at building my shed. I still think this is a useful and interesting answer, so I've +1'ed it. Unfortunately, local quarries only do a very coarse gravel, up to about 2cm on the long side of each particle, which really isn't comfortable to walk on in an environment where I'll be doing fine crafts and can't afford to trip up; the other problem with such coarse gravel is if I drop a drillbit, screw or whatever, I will never find it again. If pea-gravel were available here, I think I'd definitely go that route for the floors. As it is, I think pavers are best.
    – Engineer
    Jul 6, 2017 at 7:17

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