Explaining Retaining Walls

The Prossers’ wall job was the largest, most complicated project the contractor had ever tackled.

When Christine and Don Prosser moved into their Hillcrest Place home more than six years ago, they knew they were going to have to redo a large retaining wall on the left side of their property because they wanted to widen the driveway, which meant pushing into a hillside. In 2013, they hired a contractor and had the work done. But they never suspected they’d have to rebuild the entire 15-foot wall all over again this year after it began to sag and bulge.

It turns out, the first contractor took some shortcuts, the Prossers say. And while he did refund some of their money to put toward another contractor’s redo of the work, it meant more time with a mess of a backyard and more cash out of their pockets to get it done right.

This time, the Prossers took their time, asked questions and found a contractor who not only redid the failing wall, but added two additional retaining walls and a white picket fence in their backyard to create an attractive and safe terraced play space for their two children, ages 6 and 3. The wall and relatively new wooden staircase through the back of the property took their yard from a bumpy set of hills with random rocks as steps, to a structured and manicured space that makes it easy to supervise play. The job took from April through July, required 250 tons of gravel for drainage and 1,700 85-pound blocks.

The wall is 15 feet tall in some areas and six feet in others, framing two sides of the yard.

The driveway sits about 15 feet above the neighbors’ yard, so it was critical for the wall to be done safely and securely.

Randy Carretta, owner of RandScapes, created the wall system, made of interlocking beige blocks. “It took a lot of planning,” he says of the job, which is the largest and most complicated project he’s done in his 10 years of wall construction. “It was quite the process.”

Mt. Lebanon requires a permit for retaining walls of two feet or taller. For walls taller than four feet, residents must have an engineer design the wall in accordance with Mt. Lebanon’s grading ordinance. “You just can’t use blocks that you buy at Home Depot and stack them up,” says Mt. Lebanon’s Chief Inspector Joe Berkley. The permit will also clarify whether the wall needs to have a fence on top to prevent falls.

The work will require inspection at several intervals, Berkley says. The site needs to be inspected initially, then again when the wall is halfway done. If it’s higher than six feet, inspections may be done more frequently to monitor the work for the safety of both the property owner and the neighbors. “When it fails, it ends up in someone’s yard,” Berkley says.

Common materials for walls in Mt. Lebanon are natural stone, concrete block, brick-faced concrete block and landscape timbers.

Sometimes, the best answer to a retaining wall is having none at all. If the property can be graded properly and safely, it can be cheaper and easier to maintain in the long run, says Berkley.

For her part, Christine Prosser, an industrial engineer, says she wants others to learn from her mistakes. “Learn what your building permit means. Make sure your contractor knows what it means,” she says. “If you don’t know, ask.” The inspection office is a good resource to answer questions and to get helpful suggestions. For example, Berkley says he would likely recommend retaining walls adjacent to driveways be constructed from a material thick enough to stand up to de-icing materials.

Don and Christin Prosser stand behind part of a large retaining wall built along the perimeter of their Hillcrest Place back yard with their sons Logan, 6, (left) and Liam, 3. Besides creating a level play space for their boys, 250 ton of stone was used to create the walls along the rear perimeter of their yard.

Prosser suggests paying attention to detail. When you get a quote, have it broken out into labor and supplies. The labor should be similar to other contractors’ bids, but if the supplies are vastly different in price, find out what products they plan to use. Are they using the proper gravel? Are they using the right geogrid (a woven mesh that helps hold the soil in place)? Are the footers proper? Has the engineering work been calculated right and has the soil been tested?

“Ask for a detailed quote,” Carretta says. “Never just go for the first price or the lowest price. … You get what you pay for. People are more expensive for a reason.”

Good sources of info about supplies are plentiful in our region. Carretta says you can get advice at Homecraft True Value Building Center, Library Road, Option Supply, Brownsville Road and Tar Driveway Supplies, McLaughlin Run Road.

“For us, it was an expensive mistake to do again,” Christine Prosser says. “But you learn.”