Retaining wall cost:what decides the price

Retaining wall cost is driven first by height, then by length, material, what sits above the wall, and the base, drainage and backfill behind it. Height matters most because a taller wall holds back far more soil and water, which brings in geogrid, deeper digging and sometimes an engineer and a permit. Gerrior Masonry of Woburn builds block, fieldstone and granite walls and prices each one after a free look at the slope.

Wall height: the biggest factor

The soil behind a wall pushes harder the taller the wall gets, and that push grows much faster than the height does. A garden wall a couple of courses high is mostly a matter of a good base and straight, level courses. As a wall gets taller:

• The base trench gets wider and deeper, and more of the first course is buried.
• Segmental block walls need geogrid, a strong mesh laid between courses that reaches back into compacted soil. The taller the wall, the more layers and the longer each one, which means more digging behind the wall.
• More drainage stone and compacted backfill go in behind it.
• Past roughly four feet, or sooner when the wall holds up a driveway or a slope, a wall may need a building permit and an engineer's design; your town's building department decides.

That is why a wall twice as tall usually costs well over twice as much. Two shorter terraced walls with a planting bed between them are sometimes a better fit than one tall wall, as long as they are set far enough apart that the upper wall doesn't load the lower one.

Length, shape and the extras

Length adds cost more predictably than height. Curves, corners, and ends that turn back into the slope add cutting and fitting. Steps built through the wall and caps along the top are separate pieces of work. In North Reading, the round-fieldstone walls around the pool have granite steps set right through them, the kind of detail that adds labor and makes the wall usable.

What the wall holds up

A wall holding back a flat lawn carries far less load than one with a driveway, a parking area, a pool deck or a steep bank above it. Engineers call that extra load a surcharge, and it calls for a stronger design: more reinforcement, a bigger base, sometimes an engineer's plan even on a shorter wall. The raised, block-faced edge of the Billerica pool deck is a wall like that. It carries the deck and everyone on it, not just soil.

Block, fieldstone, granite or something else

• Segmental block. The units are uniform and interlock, so they go up efficiently and handle height with geogrid. For a wall of any real height it is usually the most economical choice. Unilock and Techo-Bloc are among the brands we install.
• Fieldstone. Every stone is chosen and fitted to its neighbors by hand, so labor is the main cost, and how tightly the stones are fitted changes it. It is the classic New England stone wall look.
• Granite. Heavy blocks, often set with a machine, and the most durable option. Common for steps, caps and walls meant to last generations.
• Poured concrete. Needs forms and steel reinforcement, and is often what an engineer specifies for a tall structural wall. It can be faced with stone veneer for looks.
• Timber. The lowest cost at the start, but wood in wet ground rots, so it tends to be the wall you pay for twice.

The half of the wall you never see

Much of a well-built wall's cost is in work that ends up underground or behind the face: excavation and hauling away the soil, a compacted crushed-stone base, clean drainage stone and a perforated pipe behind the wall, somewhere for that pipe to drain (daylight at the end of the wall, a drain line or a dry well), compacted backfill placed in layers, and geogrid where the height calls for it. Our retaining walls page explains why each piece matters for the wall's life. For cost, the point is simple: the face you see can be the smaller half of the job.

Site conditions

• Access. Can a machine reach the wall line, and can block or stone be delivered close to it?
• Ledge and boulders. Bedrock or large rocks in the trench slow the dig and can change the design.
• Water in the slope. Wet ground or a spring coming out of the bank means more drainage.
• What is near the wall line. Trees, roots and buried utilities. Dig Safe marks the utilities before any trench is dug.
• Wetlands nearby. Work close to wetlands or a stream can need conservation commission review.
• Restoration. Putting lawn, beds and walkways back afterward.

Retaining wall repair cost: fix or rebuild?

For a wall that is tipping or bulging, the cost depends on how much of it has failed and why. If one section moved because a downspout or a blocked drain soaked the soil behind it, that section can sometimes be taken down and reset with proper drainage while the rest stays. If the whole wall was built without a base or drainage, or was built taller than its construction could carry, it usually has to come down and be rebuilt, and taking the old wall out adds to the cost. Rotted timber walls are almost always replacements. The retaining walls page covers what we look for on a failing wall.

What makes a cheap retaining wall quote cheap

• No drainage stone or pipe, with the dug-out soil pushed straight back against the wall.
• A thin base, or a first course sitting on the ground instead of buried below it.
• No geogrid on a wall tall enough to need it.
• No mention of a permit or engineering for a tall wall, or one under a driveway.
• Caps set loose instead of glued down.

A wall built that way can look the same as a good one for a season or two. Then water and frost find it.

How to compare retaining wall quotes

• Same height and length, measured the same way? Ask whether height is measured from the bottom of the base or from the ground.
• Same material, with the block line or type of stone named?
• How deep is the base, what drainage stone goes behind the wall, and where does the pipe drain?
• How many layers of geogrid, and are an engineer's design and permit included if they are needed?
• Are removing an old wall, hauling soil and restoring the yard included?
• Is the contractor insured, and what does the guarantee cover?

How Gerrior prices a retaining wall

We walk the slope with you, look at where the water goes, measure the height and length the wall needs, and talk through block, fieldstone or granite. Then we price that wall for that site. If it is likely to need an engineer or a permit, we tell you at the estimate. The visit is free. Gerrior Masonry & Landscape Construction is family-owned in Woburn, has built walls across greater Boston for over 30 years, is fully insured, and guarantees its work.

See our retaining wall services, browse landscape wall photos, or, if the wall is there to make room for a patio, read the paver patio cost guide.