Retaining walls in South Portland, Maine.
South Portland is mostly low. The city's comprehensive plan puts its average elevation at about 26 feet, with the highest natural ground, around 213 feet, up in the northwest corner. So walls here are rarely about holding back a mountainside. They are about squaring off a sloped side yard in Thornton Heights, lifting a bed above a driveway in Meetinghouse Hill, or making a level lawn out of a lot that falls toward a brook.
What a wall is built on matters more than how tall it is. The plan describes the city's geology as Presumpscot Formation silty clay and minor sand, with numerous areas of man-made fill along the coast and bedrock close to the surface in many places.
Clay, fill and frost behind the stone
Silty clay holds water and expands when it freezes, and the pressure it puts on the back of a wall is what pushes granite veneer and block walls out of line over a few winters. A wall on this ground gets a compacted crushed-stone footing, free-draining stone behind the face, and a drain at the base that daylights somewhere lower on the lot. Around the old waterfront neighborhoods, where the plan notes filled land, the footing excavation goes until it finds material that will actually carry the load.
Where ledge is shallow, it can become the wall's foundation. A natural boulder wall can be set directly on cleaned rock, and a segmental block wall can be stepped to follow it. Rock that turns up partway along a wall line is common enough in this city that the footing plan allows for it from the start, rather than treating it as a surprise halfway through the dig.
Walls near brooks and the harbor edge
Many South Portland yards back onto water that the city regulates. The Shoreland Area Overlay reaches 250 feet from the upland edge of coastal and shoreland freshwater wetlands, and the Stream Protection Overlay covers 75 feet from Trout Brook, Kimball Brook, Mill Creek, Barberry Creek, Anthoine Creek and Gambler's Arm Brook. The Shoreland Resource Protection subdistrict is stricter still, limiting uses to those compatible with resource protection.
The city also operates under Maine DEP's 2022 municipal stormwater permit, which required an erosion and sediment control ordinance. For a wall, that means silt fence and stabilized spoil piles from the first day of digging, especially where runoff heads for one of the streams the city lists as impaired.
Granite · Boulder · Block
How we handle retaining walls
Whether it is a granite veneer entry wall with lantern pillars, a terraced boulder slope or a structural block wall behind a new build, we engineer for drainage and frost so the wall you pay for once stands for decades.
See the full retaining walls service page or everything we do in South Portland, Maine.
Retaining Walls in nearby towns
- Retaining Walls in Portland
- Retaining Walls in Cape Elizabeth
- Retaining Walls in Scarborough
- Retaining Walls in Falmouth
- Retaining Walls in Westbrook
More services in South Portland
- Hardscaping in South Portland
- Landscaping in South Portland
- Landscape Design in South Portland
- Planting & Garden Beds in South Portland
- Hydroseeding, Sod & Turf in South Portland
- Lawn Aeration & Overseeding in South Portland
- Fall Cleanup & Leaf Removal in South Portland
- Commercial Mowing & Cleanups in South Portland
- Excavation & Land Clearing in South Portland
- Septic Systems in South Portland
- Tree & Shrub Services in South Portland
- Tree Removal in South Portland
Sources for the local facts on this page
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