Hilly yards do not have to be unusable eyesores. Place a retaining wall at the bottom of the slope and backfill the area behind it to turn it into a garden bed or patio area. Use timbers in the retaining wall to give the wall a natural, outdoorsy look. Purchase pressure-treated timbers made specifically for ground contact. These timbers can last to 40 years if you build the retaining wall properly.
Pound a stake into the ground to mark one end of the retaining wall's front edge. Move down a few feet and pound in another stake. Use a laser level to make the stakes straight across from each other. Continue to pound stakes into the ground every 2 to 3 feet until you reach the opposite end's corner. Pound a stake into this corner.
Dig a trench using the stakes as a guide. Make the trench 12 inches deep and 16 inches wide. Take measurements periodically to make sure the trench's width and depth remain even down the entire trench.
Tamp the trench's bottom with a hand tamper. Lay a level in the trench to make sure it does not slope. Add soil back to any low areas and tamp them again.
Fill the trench with a 6-inch layer of gravel. Smooth the gravel's surface with a metal garden rake. Use the hand tamper to tamp the gravel. Lay a level on the gravel. Add gravel to any low areas and tamp them.
Measure the trench's length. Transfer this measurement to the timbers. Generally, people use 8-foot timbers because they are more manageable. So, if the retaining wall will be 21 feet long, you will need two full-length timbers and one 5-foot timber for each level. Use a circular saw to cut the necessary timbers shorter. Paint the cut ends with a wood preservative.
Drill 1/2-inch holes through the timbers for the first level. Keep the end holes about 8 inches in from either end and centre a third hole.
Set the first timber in the trench. Push it's front edge tight against the stakes. Place a level on the timber. If you have been careful to make the soil and gravel as level as possible, the timber should be level. Lay a scrap 2-by-4 board on the timber's low end and hit the board with a hammer to level the timber, if necessary. Lay the remaining timbers in the trench and level them.
Cut 3-foot lengths of 1/2-inch rebar, using a hacksaw. Insert one rebar piece into each drilled hole and pound the stake down until its top is flush with the timber's top.
Lay the second layer's timbers on top of the first layer. Stagger the timber's meeting joints. Do this by starting the cut timber on the opposite end from the first layer's cut timber. If you do not have a cut timber in the first layer, cut one timber in two and lay one half timber on each end to stagger the meeting joints. Secure the timbers in place with pressure-treated-wood screws every 8 inches.
Lay landscape fabric in the trench behind the timbers going up the slope. Lay a 4-inch perforated pipe behind the retaining wall's first two levels, on top of the fabric. Make sure one of the pipe's ends extends past the wall so it drains water away. Cover the pipe with more gravel and fold the fabric over the pipe.
Build up the timber retaining wall two more levels. If you go higher than four levels, use deadmen to help stabilise the wall. To make a deadmen, cut one timber to 2 feet long and a second timber to 4 feet long. Place the 2-foot timber on top of the 4-foot timber to form a T. Screw the two pieces together with pressure-treated wood screws. Backfill the area behind the retaining wall with soil. Center the deadmen behind the retaining wall with the bottom edge of the "T" lined up with the retaining wall's front. Level the deadmen and secure it to the retaining wall with pressure-treated wood screws. Continue to build up the retaining wall.
Drill 1/2-inch holes through the deadmen's cross timber. Place one hole on each end. Cut 1/2-inch rebar 24 inches long. Hammer the rebar into the deadmen until they are flush with the timber's surface.
Back-fill behind the timber retaining wall until the surface level is equal to or slightly lower than the retaining wall's height. Use a garden hose to moisten the soil, causing it to compact. Add more soil as necessary.