ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Sunday, September 1, 1996 TAG: 9609040137
SECTION: HOMES PAGE: D-1 EDITION: METRO
COLUMN: Hints for homeowners
SOURCE: STEVE ELDER
Most masonry contractors with long experience have developed their own methods of paving patios. There are many different ways of doing the job, depending on budget, site and the desired effect.
If someone tells you, ``This is the only way to do it,'' you may be talking to a person with one year's experience repeated several times as opposed to a person with several years of experience.
As the caterpillar said to Alice, ``Begin at the beginning.'' First, decide on a design for your patio. Budget permitting, I tend to recommend that this be done by a professional landscape architect or designer; this generally increases your chances of a good-looking end product. The budget will also determine what method for laying patio brick or stone will be chosen, either the less expensive flexible base or the more expensive permanent base. All the various paving techniques ultimately fall into these two main categories.
Flexible base paving means laying the paving brick or stone on a bed of sand. The durability of this method depends greatly on doing the preparatory work carefully. First, the ground should be excavated to a depth of 5 to 6 inches below the intended finish grade. Then the borders should be set. Borders can be installed in a number of ways.
One common method is pegging pressure-treated 6x6's firmly to the ground by using 2-foot lengths of half-inch rebar (iron reinforcing rod) driven through drilled holes in the 6x6's at four-foot intervals. (Do not use railroad ties. They last a long time when bedded on raised crushed stone but will rot fairly quickly when on the ground in contact with clay soil.)
Another way to set borders is to form and pour concrete curbs. Regardless of type, the border must be firmly secured, otherwise the sand base will spread over time and cause unsightly gaps and depressions in the paving.
All organic matter should be removed from the field and the dirt firmly tamped. It is advisable to put a slight grade on the dirt bed to provide subsurface drainage. This grading will help prevent low spots from collecting water, becoming soft and causing the paved surface to sink over time. Next, fill the area with 3 to 4 inches of sand and screed it to a uniform depth of 21/4 inches. Some contractors put down a layer of 30-pound roofing felt to discourage weed growth; but if you do this, make sure you have put a slight slope in the field for drainage. Then lay your brick or stone in the desired pattern. (Tip: You may wish to rent a brick saw from a tool-rental center for the weekend. It will do a much faster and cleaner job of brick-cutting than using a brick hammer.)
If you're using brick, be sure it is paving brick. Brickmaking is a 5,000-year-old art, and there are many different kinds of brick. Core brick has holes and is used for laying up brick walls. Paving brick is solid and is fired at higher temperatures for longer periods of time to give it the necessary hardness and durability required for traffic-bearing surfaces. It is commonly available in thicknesses of 15/8 or 21/4 inches. I recommend the thicker variety for flexible bed installations. Be warned that not all solid brick is paving brick.
I usually advise against the use in paving work of old brick taken from razed buildings because old brick tends to be softer and much more water absorbent, thus causing rapid deterioration. Also, I strongly recommend laying the brick tightly, without grout joints. Since a flexible bed is subjected to some frost heave from the annual freeze-thaw cycle, mortared joints between the brick will soon start to crack and look unsightly. This is also true for mortared joints between fieldstone pavers.
If you are going to lay fieldstone instead of brick, do not use felt over the sand bed, because you will have to work the irregular bottom of the stones into the sand in order to bed them properly. After doing that, grout between the stones with fine gravel. As a rule, I recommend against flexible bed fieldstone patios, because keeping weeds from growing in the gravel grouting requires high maintenance. To finish a brick patio, dump a small pile of sand on the surface and sweep it into the brick joints.
The other major paving method is to lay the brick or stone on a permanent base, which normally means a 4-inch thick concrete slab poured over a crushed stone base. ``Permanent'' in this context actually means ``immobile.'' A sand-base paving job, if done right, is also ``permanent'' in the sense of being long-lasting. The difference is that it will flex slightly with freeze/thaw cycles, whereas the concrete-base paving job will not. On a concrete base the brick can be laid with either tight joints to be sand-grouted as described above, or with spaced joints to be grouted with mortar.
The bricks or stones are usually bedded in a thin layer of mortar. On larger commercial jobs such as sectional street paving, you may have seen hot tar used as a bedding compound, but this is usually not practical for patios.
If you use a standard mortar bed, be sure to dampen the concrete bed and the bricks, particularly on hot days. Brick is porous to some extent. If it is too dry, it will leach the water out of the mortar before the chemical bond has a chance to form. (This is true of bricklaying in general.) If you plan to space the bricks and grout with mortar, try to strike the mortar joints as flush to the brick surface as possible, to give a smooth walking surface. Granted, there is some work involved in doing a paved patio; but the end product is usually worth it.
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