Diy Flagstone Patio: Common Problems And How To Avoid Them

How to avoid the common problems of flagstone cutting and uneven surfaces when installing your own falgstone patio.

You can avoid problems when laying your own flagstone patio with a little up-front planning and preparation. Some problems may occur during the patio installation. Other problems develop over time. Both categories of problems are discussed here.

Getting an even surface is probably one of the most common problems with a flagstone patio. An uneven patio surface can be caused by stones of varying thicknesses, an uneven base, and settling. All three of these common problems can be avoided.

Since flagstone is a naturally occurring material, completely eliminating variation in thickness is not feasible. However, picking your own stones from the supplier's yard will minimize differences. If possible, you should select stones that are 1 to 2 inches thick. You want to avoid significant changes in thickness on a single stone as well between stones. Thinner flagstone can be used if your base is highly stable. However, thinner stone will be less durable most of the time. Stone thicker than 2 inches will be very heavy and difficult to handle. If you are picking a pallet of stone for delivery, you should try to choose a pallet with stones of consistent thickness.

An added benefit to picking and loading your own stone is that you'll know you can lift each of the pieces. Imagine having a pallet delivered to the street and finding in the middle of the stack a single piece as big as the pallet and 2 or more inches thick. Your best course of action is to get a brick set and break the stone into a few smaller pieces for handling.

While installing your patio, you can compensate for stones with varying thickness. Lay out your pattern with adjacent stones gradually changing in thickness. This will significantly reduce the amount of leveling you do. If your flagstone has significant changes in thickness or any piece is over 2 inches thick, be sure your sand base is over 2 inches thick as well. Otherwise, you won't be able to level the stones.

Having a level base to start with means less effort is required to get a level patio. To get a level base, use fill to eliminate holes and minimize slope. Roll or tamp the fill. If your soils haven't been disturbed for a few years, they should be stable and you should have little need to use fill. After rolling or tamping the fill, cover the area with about 2 inches of patio sand. The sand layer needs a light misting of water to settle it. Then rake smooth.



Settling over time may result in an evenly installed patio becoming uneven. If you live in an area with a lot of rain fall, you should consider installing a drainage system before you lay down the flagstone. This is especially important if you are going to mortar your stones in place. If your planned patio area doesn't have stable subsoil, increase the stability of the area with gravel, fill, and sand. Each layer must be well-tamped and level. If you don't mortar your flagstones in place, you can re-level an area that experiences settling using the same techniques as during the initial installation with a level, shovel, and patio sand.

Avoiding an uneven patio during the installation process is easiest using a level on each stone. Once you have your pattern in place, check for level on the diagonals of the stone. Then check the level from one stone to the next. Based on the areas to be raised and lowered, take patio sand away, add it, or move it from a high spot to a low spot. Leveling each stone as it is placed in its final position is much easier than trying to level the entire patio at once.

Laying flagstone over a concrete pad will minimize the amount of leveling you need to do. Future settling is also unlikely when using a concrete pad as a base. Only a half inch to one inch of sand is required over concrete - just enough to accommodate leveling due to varying stone thickness. You can also use thinner stone over a concrete pad without much impact on durability.

If your patio area lends itself to a free-form shape, you can avoid the need to cut straight edges on your flagstone. If your area has rigid boundaries, taking a good sketch to the supplier is vital. Selecting several flagstones with long straight edges will minimize the amount of cutting needed. Pre-cut flagstone squares are also a good solution to making cuts on flagstone later. Your supplier can likely make cuts for you for an extra charge. If you have a sketch with dimensions and are using pre-cut stones, the supplier can make necessary cuts for you right away. If you are using uncut stones, you will need to lay-out your pattern, mark the stones to be cut, and bring them back to the supplier. Making a few cuts yourself is reasonable using a sledge hammer and brick set. However, if you want to make a significant number of precise cuts yourself, you should use a diamond bladed saw.

If you don't want to plant between your flagstones, consider using mortar in the joints. This will also give you a more stable and even surface for furniture and walking. Mortar between flagstones installs easily and is durable with a few simple practices. Mix the mortar in a wheelbarrow to easily move it around the site. Only mix enough for an hour at a time - mortar can be re-moistened somewhat with a little water. Wash off smears that cling to the stone before they dry. Small dried smear areas can be cleaned with alkali soap and rinsed with vinegar to remove stains. When complete, cover the wet mortar areas with black plastic sheets. This will slow the drying process maximizing strength and durability.

Flagstone thickness and adequate base preparation are two keys to avoiding multiple common problems with flagstone patio installation. Plan well up-front and your flagstone patio will last for years.

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