Establishing a base for patio furniture

All patio surfaces are made with one thing in common? And that is to provide a level area to place furniture, barbeques etc

In an earlier hub I discussed in detail the types of surfaces that are more commonly used in the making of patios. In this, I would like to go into further detail on how to construct and prepare the ground for the most common type, which is a concrete slab. Although the casting of the slab doesn't have to remain with the concrete finish. You can then cover the concrete base with a tile or a stone such as in the photo below. This is actually pieces of broken stone randomly placed to form a very interesting patio surface, that would look great with the right type of patio furniture.

Although the purpose of these articles are to explain the basic principals involved, you should take great care in the planning of your chosen area, as each particular shape, and product it is made of brings along it’s own little problems. One of these common problems would have to be drainage.

Whatever type of material you choose, you must make certain that adequate drainage is provided. Failing to do so will amount to a very costly exercise to remedy the problem. Take a look at your proposed site? Generally speaking, a patio would normally be adjacent to a wall belonging to your house, and so therefore you may be able to connect into the house drains, but there are occasions when patio surfaces can find themselves a few feet away, which would leave you the problem of providing necessary drainage.

Before commencing such a project, check first with your local building codes, as they tend to vary from country to country, and state to state. It would not be logical for me to make provisions for every by law that may exist.

For the purposes of this article I’m going to use an example of a new house that has just finished completion, and the builders have long gone leaving you with a plot of soil that has never seen a landscaper.

Concrete:

A concrete base will be poured to a thickness of 4”, on top of a sub base of 2” of aggregate, or loose rock,. So you will need to remove 6” of soil with the aid of a mechanical digger, go ahead and remove the unwanted soil. If you feel strong, you can remove the soil by hand.
Once removed, you need to level the surface, either using a rake, or you can use a piece of lumbar cut to the width of your intended patio, having someone to help, you can use the timber to drag along the surface removing any highs, and filling any lows.

This would be an ideal time to put in your drainage. The slab you’re going to create can either butt directly against your house incorporating a few degree of fall, so that any water will run away from the house into a drain in the middle of the patio. Or you could insert a 4” storm drain to run the length of your house, directly seated against the wall. And the slab will incorporate a fall towards the house. Providing you seat the drains perfectly, and make sure there’s a fall along the length, in order for the water to escape, there shouldn’t be a problem. However, this is an alternative, and each site will vary. I on the other hand, prefer the former as I’ve always tried to have water running away from the building. Plus, depending on the length of your intended patio, a drain grill covering the length can look ugly, whereby choosing my preferred method; you only need to see one small grill every 12 feet in the middle of the slab.


You now need to back fill your hole with 4” of aggregate. This needs to be packed down firmly using a tool from your local hire. It consists of a gas motor with a flat 2-foot steel base that will thump the rock down, so that it’s tightly packed. This is very important. Unless you have a stable sub base, your finished surface will never be good.

You should now be 4” below your proposed height. As the concrete is to be poured, you need to make a frame in order to contain the mix. Pouring concrete is relatively simple, but you need to be prepared, and operate at a smooth efficient pace. When constructing a frame to contain the mix, you will need to allow for expansion joints along the length. If you were to cast say an 18’ slab without any expansion joints, it will eventually crack, and become uneven. Putting a joint every 6’ will allow the slab to move, and expand along with minor movements that take place in the ground. The joints only need to be 1/2" thick. See above photo.

Sounds complicated but all you do is make a frame the length and width of your patio, 4” higher than the sub base, and then split the area into 6’ sections along the length. If your patio doesn’t fall within a 6’ increment, round the figure up or down, allowing for the expansion joints (see photo) to be equally spaced. One other thing to remember is that at this stage you have the opportunity to reinforce the concrete slab with steel reinforcing rod, also refered to as rebar. This is interwoven to provide extra strength for the slab, although for a small area it's not really necessary, although it's always best to be on the safe side, and it really isn't that expensive.

You’re now ready to pour the concrete. Whether you’ve contracted a firm to deliver the ready mix, or you prefer to mix yourself on site, just pour in the mix and have someone help you spread it within the frame. Using pre cut lumbar that is long enough to cover the width, drag the timber along the top edge of your frame removing any surplus of concrete. Repeat this process until the frame is completely filled, and leveled off. It will take approximately 24 hours to cure. If you require your slab to be smooth, trowel the surface when wet with a brick trowel. If you require a rougher surface, you can go over the surface just before it dries with a yard broom that has a hard bristle. This will gently take off the top smooth surface.