Why not build a wall this winter?

Are you looking for a winter project that will add a sense of solidity and style to your garden, while solving landscape problems at the same time? Consider building a stone wall to level a slope for a terrace or planting area.

Many wall-building techniques are well within the abilities of a homeowner, and the exercise will keep you warm on chilly days.

Retaining walls using natural stone can be built with or without mortar, a mix of Portland cement and sand. Walls built without mortar are called dry-stack walls.

For the homeowner, dry-stack walls have several advantages. Mortared walls require concrete footings reinforced with steel to prevent the wall from breaking up when soil settles over time. Dry-stack walls can move with changes in the soil without coming apart, so don't need rigid foundations.

Also, a dry-stack wall can be built at a more leisurely pace because you don't need to worry about mortar setting up, and it's the method I suggest for initial projects.

Visit a stone yard to choose the right stone for your wall. (Find one in the directory under "Stone — natural.") Most have demonstration areas showing a variety of stones and construction techniques.

Flat stone is easier to stack than rounded stone. Think about the size of stones, too. Smaller stones are easier to lift into place, which is important for your back.

More information

Many books provide good information about wall building. One, by Seattle author Jan Kowalczewski Whitner, is "Stonescaping: A Guide to Using Stone in Your Garden" (Storey Publishing, $18.95).

Freestanding walls: Although this article deals with retaining walls built to create changes in level, stone walls also can be freestanding. For hundreds of years, farmers have built dry-stack stone walls to separate fields, using stones cleared from the land. For more information, visit the Web site of the Dry Stone Walling Association of Great Britain at www.dswa.org.uk.

Above all, choose a color and texture that appeal to you.

Consider the height of your wall. Walls taller than 3 feet might need a permit and an `engineer's plan. Check with your local municipality for regulations. To reduce the height of a wall, consider leveling a slope by using two shorter walls stepping up the hill instead of a single taller one. Retaining walls about 14 to 20 inches tall can serve double duty as seating, which is useful when you are entertaining a crowd.

Time to start building

Building a wall is like putting together a three-dimensional puzzle.

How many stones in my wall, Phil?

There's a way to estimate how much stone to buy. Multiply the length of your planned wall by its height to calculate how many square feet of front surface, also called face feet, are in your project. Then check with the stone yard to find out how many face feet per ton the stone you're interested in will cover, since it varies with the type of stone.

First, mark out the face of the wall with stakes at each end and string running between them.

Next, create a solid base for the wall. For short walls a foot or so high, tamp the soil down where the stone will go. For a taller wall, or if the soil is wet clay, excavate a trench eight inches deep and fill it with four inches of packed gravel for a firmer foundation and to put the base of the wall below the finished soil line.

For the first course, use the largest stones to anchor the wall. While laying succeeding courses, remember the phrase, "one over two and two over one," placing a stone so that it rests on two stones beneath. This staggers the joints in the wall and increases its strength.

You might need to use a hammer and a stone chisel to take off parts of a stone to make it fit better. Use smaller pieces of rock as wedges and shims to stabilize individual stones.

As you build, taper the wall back about two to three inches for each foot of wall height, so the wall leans into the hill.

As each course goes up, fill in behind it with soil and tamp it down. In walls taller than 2 feet, backfill with gravel to provide drainage that will keep water from backing up behind the wall, particularly in clay soil.

Step back occasionally from the wall to check the overall effect. Good walls have a lively flow to the pattern. Save the flattest, widest stones to make a cap for your wall, giving it a finished look — and a comfortable seat.

Phil Wood has a degree in landscape architecture and designs and builds gardens. Send questions to thegardendesigner@seattletimes.com. Sorry, no personal replies.