Q. I am planning to add a paver patio to my house. What is the best way to build the base? Can I install pavers over concrete?
A. I assume you mean interlocking concrete pavers, which are used for many patios, driveways and sidewalks because of their durability and good looks. A base for paving bricks can be constructed in the same way. I can give you an outline of the proper way to install a base, which can help you decide if you want to do the project yourself or hire a pro.
If you decide to try DIY, your paver dealer should be able to provide more specific directions. The dealer should also be able to supply or give sources for the special gravel and sand for the best installation.
The first step is to excavate the soil in the patio area to a depth of 7 to 9 inches. Make the excavation about a foot larger than the finished patio size, to hold an edge that will hold the pavers in place. The edge can be a concrete curb, treated wood timbers or even special plastic edge.
When the excavation is complete, the soil on the bottom should be compacted with a machine that can be rented at some tool-rental agencies. A layer of gravel of mixed sizes, at least 4 inches thick, is then added and compacted. A 1-inch layer of sand goes on top of the gravel. A screed – a long, straight-edge board – is used to smooth the sand by pulling it across the sand.
The depth of everything you add to the excavation should be carefully calculated so that, when the pavers are added and the finished surface compacted, the patio is at the level you want.
A somewhat simpler way to install pavers is to skip the excavation and build a frame using treated wood, such as railroad ties, and use it to hold the gravel, sand and pavers in place. Pavers can be installed over concrete, usually if there is an existing concrete slab in good condition that you want to improve. Deteriorated concrete should be removed. Most concrete installers use an inch or more of sand to bed the pavers.
Q. I was told I should replace the insulation and the plastic ground cover in my crawl space. Do I really need both insulation and the ground cover?
A. Insulation and the ground cover serve different purposes, and you probably need both. The main purpose of insulation is to help keep heated or cooled air from escaping the living area. Insulation in crawl spaces is recommended in every region, including those with the warmest climates. The minimum recommended level of insulation for most of the nation is R-19, which is equivalent to about 6 inches of fiberglass.
In cold-climate areas, much thicker insulation is recommended.
To check the amount of insulation recommended in your area, visit www.energystar.gov and type “recommended levels of insulation” in the search space. The purpose of a plastic cover over the floor of a crawl space is to prevent moisture from rising from the soil and filling the space with water vapor, which can condense on cool surfaces and cause such problems as mold and rot in structural parts. This cover is especially important in crawl spaces with earth floors. Plastic at least five mils thick (five one-thousandth of an inch) is recommended. The cover should be held in place with bricks or stones and should extend up the wall about a foot (use high-quality duct tape to hold the overlap in place).