How to Install or Lay Flagstone Pavers When Building a Flagstone Patio
Flagstone is a rather generic term for large, fairly thin slabs of stone pavers used for building walkways or patios. They are available in a wide range of sizes, from around a square foot to large slabs that measure several feet in length and width and come in a range of colors.
Installing a flagstone patio is much like putting together a puzzle: the pavers are very uneven in shape and size and yet must fit together with a minimum of cracks between pavers. As the stone is difficult to cut, it is preferable to use pavers as they are purchased, without modification. A variety of sizes is thus useful as it is often impossible to fit large pieces together without leaving large areas to be filled.
In general, flagstone is set into a sand bed, leveling each piece as it is laid. Areas between pavers are then filled with additional sand and compacted. A compactor of some kind and a rubber mallet are about the only specialty tools needed, and this makes the task of installing a flagstone patio well within the capabilities of the homeowner willing to put in some effort. And it does take a good bit of work. The ground needs preparation, sand hauled to the site, and the puzzle of pavers carefully assembled.
Preparing the Area for the Patio
The patio described and used for the pictures in this article was in the corner to a sunroom addition that already had a concrete stoop in front of the door and an additional small concrete patch used to park a gas grill on. One end of the area was simply dirt (and weeds) while the rest was lawn that would need removed. As the sunroom was built on a concrete patio the door was just above the lawn and this limited the height of the finished patio as it had to fit under the door and yet drain away from the home as much as possible.
The project was very limited in funding and considerable savings were found in an old flagstone walkway that had been put into the lawn years before. These pavers were pulled up and used in the new patio, with additional pavers being purchased as needed. New pavers were to be of a very light color, with some gold running through them as well, so the old, reddish brown existing flagstone was planned to go around the edges of the patio with the new pavers to be set into the center.
Two by fours were used to line out the space for sod removal, but stakes with string or spray paint could be used as well. Sod was removed and used to re-fill the holes in the lawn where the old flagstone pavers were taken out. Additional dirt was removed to allow some 2 to 3 inches of sand to be added followed by the pavers; the top of the pavers were to be approximately level with the surrounding lawn. An additional ½" of height would have been preferable but as the patio had to fit under the doorway that would have caused the drainage to be toward the house. Even though a flagstone patio will allow water to drain through it, it is still always preferable to drain away from any structure.
A flat, square shovel was used to level the exposed soil as much as possible. The objective here is to have a very slightly sloped flat surface for the sand. A slope of about ¼" per foot is fine but much more than ½" per foot will be visible and annoying. Any imperfections where a little too much dirt is taken out should be left; it is preferable to have undisturbed soil to lay the sand on and an extra inch or so here and there can be simply filled with sand. If dirt is used to refill any holes created it must be compacted before adding sand.
The concrete was broken up with a sledgehammer and removed. Not a pleasant task, but possible as there was no rebar or steel mesh in either the stoop or the grill base.
Preparing the Site
Adding Sand to the Area
The next step in building the patio was adding the sand for the pavers to sit on. There were two types of sand to consider: play sand and "compaction" sand. The latter is preferable as it contains small stones as well as some very fine sand and compacts well.
As funds were limited, a heavy steel roller was used for compaction. This is not comparable to a plate compactor but was available for no cost rather than renting a compactor. A thin layer of around 1 inch was spread and raked smooth and then rolled several times with the roller. Water can be sprayed on lightly to aid compaction and was used prior to the final rolling.
Additional sand was added in 1 inch layers to achieve the final goal of around 2 to 3 inches, compacting each layer. As the old pavers varied a great deal in thickness and were not equal to the new pavers by any means this was done only around the edges, projecting about 2 feet into the area to be paved. After the old pavers were all installed into the area sand was added to the center portion of the patio with a better idea of how thick it should be and that area compacted with the roller.
Adding the Sand
Laying the Pavers
The old pavers were very uneven in thickness, varying from ½" thick to around 3". This required removal of sand (or addition) so that the pavers would be at the correct height. In addition, the pavers were often uneven in individual pieces; the sand must be also uneven. Each piece was set into the area, wiggled to provide an impression in the sand and the sand then added/removed to match. A time consuming process.
Several pavers were placed into the area and fit as well as possible. Only then were individual pieces actually set into the sand using the process above. This made it possible to find the best puzzle piece fit for a good sized area before going to the work to actually set the pavers. As each was set a rubber hammer is used to tap the paver into the sand. It is absolutely necessary that each and every inch of each paver be in good contact with the sand or it will wobble and likely break after time and traffic.
The hammer used was a "dead blow" hammer; a plastic/rubber hammer that is filled with lead shot and provides a much heavier blow without the additional weight. It worked very well, but a regular rubber mallet will also do well.
Particularly towards the end of the project smaller pavers were necessary to fit into the open spots. A diamond blade saw is needed to actually cut pavers, but they can be broken with moderate success by laying them over a 1" steel pipe and striking one side with the hammer. Do not use a steel hammer for this; it will only shatter the paver into a thousand pieces instead of breaking it on a semi-clean line. At best, however, any breaks will be only approximate and it is preferable not to try to break the pavers but to use them as they are. For this reason it is best to get some large as well as small pieces. Larger pieces can be nice for appearance but smaller pieces will be required as well to fill gaps and fit properly.
Finished Flagstone Patio
Costs were most reasonable: our totals were $40 for sand (purchased bulk) and $90 for flagstone pavers. This produced a patio 8X12 feet, or just about 100 square feet. The paver cost would have doubled had the old pavers not been available. We were told that it would require 1000 pounds of flagstone to cover 100 square feet, but a different employee told us 2000 pounds would be necessary. The former figure proved accurate; 550 pounds were purchased for just about 1/2 of the project with the rest being old pavers removed from the yard.
While I am pleased with the appearance, I feel that more effort might have resulted in smaller cracks between pavers. Or perhaps I'm just not a very good puzzle maker. The two different colors go well together and have made a pleasing pattern that I am happy with.
The bottom line is the $130 and two days of hard work have produced a flagstone paver patio that takes the place of a very ugly and useless area. Overall, I am very pleased.
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© 2011 Dan Harmon