Basic Patio Construction
Following some basics of construction will ensure a successful patio project.
All patios need to be built on a level surface no matter what materials you end up using. Cracks in concrete, uneven surfaces and pooling water on the patio can all be attributed to an ill prepared sub-base.
But there are differences in how your patio will be built depending on the hardscape material you choose. "It can take four to six weeks from the initial consultation to the finished patio," says Derek Archer, landscape designer for Brentwood Landscape & Design.
Typically, it takes about one week to install a basic patio, but longer for larger, more elaborate designs and to install plantings nearby. Here are some tips to basic patio construction.
Marking the Site
Using stakes and string, the patio will be outlined in the area where it will be built. The stakes are pounded into the ground at the corners of the patio then string is tied to the stakes to show the size and shape you want.
Sometimes builders use a type of eco-friendly spray paint to mark the area in the shape and size of the patio. This method is easier than the stakes and string method and works especially well on curving patios.
Once the patio site is marked, the builder will excavate the patio's footprint. For a poured concrete patio, they generally dig down about eight inches allowing for a four-inch thick base and four inches of concrete on top of it.
They will dig about six inches outside the marked lines of the patio to allow for the wood or plastic forms that will hold the concrete as it dries. For dry-laid patios made of paving stones, flagstones or bricks, the builder will use the same method but typically there are no forms to hold these materials in place. They use the edge of the dug out area as a guide.
Once the area is excavated, it's cleared of any rocks, roots and debris and smoothed out. They then tamp down the soil using a hand held tamping tool or a power driven tamping machine. They repeatedly check the level to make sure it is even. For a concrete patio, the forms are added along the edges of the patio. They are held in place with stakes to keep them upright and sturdy enough to hold the poured concrete. Next, a layer of loose gravel is poured into the excavated area.
It is spread out in the area and tamped down again to compact the base. A board laid across the sides of the area reaching across the patio area is used to help determine that the gravel is level. Sometimes, a layer of plastic sheeting is laid over the compacted gravel followed by a reinforcing metal mesh screen. Expansion joints made of 1/2-inch thick strips of asphalt-impregnated fiber are used every 15 feet or so set into the form.
These help prevent buckling as the concrete expands with temperature changes. Wet concrete is poured into the form over the sub-base between the expansion joints and smoothed out using metal or wood skimming tools and hand held trowels.
The builder will work in sections pushing the concrete into the forms making sure there are no air holes and helping the concrete to settle in the forms. Excess concrete is screed across the surface producing a level area. They then move on to the next section until the entire form is filled in, level and smooth.
For special textures, the surface may be brushed with a bristle broom or troweled to create a pattern. The concrete is allowed to slowly cure under a sheet of plastic for several days until ultimately, the plastic is removed and the patio is allowed dry.
For a dry laid patio such as one made of pavers, bricks or flagstones, builders generally follow the same marking, excavation, tamping and leveling methods as they would for a concrete patio. They build up the sub-base using layers of gravel, a finer crushed gravel and clean, washed sand free of any rocks or debris. They then lay the surface material into the area making sure to follow the pattern you agreed upon in the design process.
After the materials are laid out, they use sand or a fixing material that is poured on to the surface and brushed into the joints between the stones. Using a garden hose, they water-in the loose sand or fixing material to lock-in the stones. Typically, you can walk on the surface of the patio the same day, as there is no wait time for the patio to cure or dry.