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Patio Scopebook · Glossary
Hardscape glossary: the words that decide what you are paying for
Most of a hardscape bid's value sits in words homeowners skim past: base depth, bedding layer, edge restraint, geogrid, surcharge, polymeric sand. Knowing what each means lets you check whether two proposals describe the same construction. The terms below are the ones that separate a patio or wall that lasts decades from one that shifts, heaves or drains the wrong way.
12 terms you will see in patios and hardscapes proposals
- Base (aggregate base)
- The layer of compacted crushed stone under a patio, walk or driveway that carries the load and drains water. Typically 6 to 8 inches for patios and 10 to 12 inches for driveways, placed in lifts.
- Bedding layer
- The one-inch layer of coarse sand screeded flat over the base on which pavers are laid. It is never used to make up for a low base.
- Control joint
- A groove cut or tooled into a concrete slab every 8 to 12 feet to direct where the slab will crack as it shrinks and moves.
- Edge restraint
- A concrete curb, spiked plastic or aluminum edging, or mortared border along every free edge of a paver surface that stops the outer units from drifting outward.
- Efflorescence
- A white mineral haze on new concrete pavers caused by salts migrating to the surface as the concrete cures. Cosmetic, and usually weathers off within a season.
- Geogrid
- Reinforcement mesh laid between courses of a segmental retaining wall and extended back into the retained soil so the soil mass becomes part of the wall.
- Geotextile
- A woven or non-woven fabric laid between soil and base stone to keep the two from mixing, used on clay, silty or wet subgrades.
- Impervious cover
- The portion of a lot covered by surfaces that do not absorb water, such as roofs, driveways and conventional patios. Many municipalities cap it; permeable surfaces may be excluded from the count.
- Permeable interlocking concrete pavers (PICP)
- Pavers with wider joints filled with small stone over an open-graded stone reservoir, allowing rain to pass through the surface into the ground.
- Polymeric sand
- Joint sand with binders that harden when wetted, locking paver joints against washout, weeds and insects. Not used on permeable pavers.
- Segmental retaining wall (SRW)
- A dry-stacked wall of interlocking concrete units with a built-in setback, reinforced with geogrid on taller walls and drained by stone and a perforated pipe behind it.
- Surcharge
- Any load on the soil behind a retaining wall beyond level ground, such as a slope, driveway, patio or structure. A surcharge usually removes a permit exemption regardless of height.
The term list on this page defines each word on its own. This introduction explains how to put those definitions to work: reading a written proposal line by line, spotting where two contractors use different words for the same thing or the same word for different things, and turning each term into a question that gets a specific, comparable answer.
Hardscape vocabulary matters because the parts that fail are the parts you cannot see after the job is finished. A proposal that names the base material, its depth, the compaction method, the edge restraint and the drainage path gives you something to hold the contractor to. A proposal that says only patio, pavers, installed gives you very little, and Houzz's 2026 outdoor study found 41% of outdoor projects began because an existing space had deteriorated. The paver patio service page shows how these parts fit together in a finished build.
How should you use these terms when reading a proposal?
Go through each bid with a pen and mark every construction term. For each one, check that it comes with a number or a specification: a base depth in inches, an aggregate size, a paver thickness in millimeters, a wall height, a geogrid length, a drain type and outlet. Terms without numbers are placeholders, and placeholders are where cheaper bids usually save money. Write the missing figures in the margin as questions before you compare prices.
Next, line the bids up side by side on the same terms. If one proposal specifies a six-inch compacted base with concrete edge restraint and another says only prepared base with edging, the price difference probably reflects different construction rather than a better deal. HomeAdvisor's June 2026 average interlocking paver job is $3,400, and these terms decide where a bid sits around it. The hardscape cost guide shows which of those details carry the most money, and the planning tools help turn them into a consistent scope you can send to every bidder.
Which hardscape terms are most often confused?
Base and bedding are the classic pair. The base is the thick layer of compacted crushed stone that carries the load; the bedding layer is the thin screeded layer, usually about an inch of coarse sand or fine chip stone, that the pavers sit in. A bid that describes an inch of sand as the base is describing a patio with no real foundation. Similarly, geotextile and geogrid are not interchangeable: fabric separates soil from stone, while grid reinforces the soil behind a wall.
Edge restraint and edging also get blurred. Decorative edging is a visual border; edge restraint is the structural element, spiked plastic, metal or a concrete curb, that stops the pavers from spreading outward. Control joints belong to poured concrete and have no equivalent in pavers, where the joints themselves allow movement. Impervious cover and permeable pavers are linked in local rules, so check how your municipality counts them before assuming a permeable surface is exempt.
- Base versus bedding layer: inches of compacted stone versus about one inch of screeded material.
- Geotextile versus geogrid: separation fabric versus soil reinforcement in walls.
- Edging versus edge restraint: appearance versus structure.
- Polymeric sand versus plain joint sand: a binder that hardens versus loose fill that washes out more easily.
What questions do these terms unlock with a contractor?
Each term turns into one direct question. Base: what depth and material, compacted in how many lifts, and with what equipment? Edge restraint: what type, and how is it anchored? Segmental retaining wall: which block system, how tall, and does it need geogrid or engineering at that height? Surcharge: is there a driveway, slope, fence or structure above the wall that adds load? Efflorescence: how will it be handled if it appears in the first season?
The answers matter more than the vocabulary. A contractor who answers in specific numbers and names the manufacturer's installation guide is describing a repeatable process. A contractor who answers that they always do it that way, without figures, may still do good work, but you have nothing to compare or enforce. Houzz found 20% of outdoor renovators hired a stone, paver or concrete specialist, the trade most fluent in this vocabulary. The planning quiz covers many of the same questions and can help you decide which matter most for your yard.
Which terms matter most for walls, drives and drainage?
For retaining walls, the key terms are segmental retaining wall, geogrid, surcharge and drainage aggregate behind the wall. Height thresholds in local codes, often tied to the 4 feet exemption in the 2024 International Residential Code, decide when engineering and permits apply, and surcharge can trigger them sooner. For driveways, the terms are base depth, paver thickness and edge restraint, because vehicle loads punish shortcuts. For drainage, watch for slope expressed as a percentage or inches per foot, and for where the water finally goes.
Permeable interlocking concrete pavers bring their own vocabulary: open-graded base, reservoir depth, underdrain and joint aggregate. These are not optional extras; they are what makes the system work. If a proposal calls a surface permeable but prices a conventional dense-graded base, it is not a permeable system; the EPA's fact sheet puts true permeable interlocking pavers at $7 to $14 per sq ft to build. The permeable versus conventional comparison explains how the two builds and budgets differ.
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Glossary questions
What is the single most important term to check in a patio bid?
Base depth and material. Most paver failures, such as sinking, ruts and heaving, trace back to a base that was too thin, poorly compacted or built from the wrong aggregate. A bid should state the depth in inches, the type of crushed stone and how it will be compacted.
Why do contractors use different words for the same part?
Regional habit, manufacturer terminology and training all play a part. One firm says bedding sand, another setting bed, another screed layer. Ask each bidder to describe the part in terms of depth and material so you can confirm they mean the same thing before comparing prices.
Do I need to understand engineering terms for a small garden wall?
Not in depth. For a short wall with nothing heavy above it, the terms that matter are the base under the first course, drainage stone behind the block and a way for water to exit. Engineering vocabulary becomes important as walls approach the local height threshold or carry a surcharge.
Is polymeric sand always better than regular joint sand?
Not always. Polymeric sand resists washout, weeds and ants when installed correctly, but it can haze the paver surface or fail to set if it is applied wet or to a joint that is too shallow. Some permeable systems use open aggregate instead. Ask which product will be used and why, and how it will be topped up: HomeGuide prices professional sealing with re-sanding at $1.50 to $3.25 per sq ft, which includes pressure washing, so ask whether topping up the joints is part of that visit or a separate charge.
What does it mean if a bid mentions impervious cover?
It means the contractor is aware that your municipality may limit how much of the lot can be covered with surfaces that shed water. Adding a large patio or driveway can push a lot over that limit, which may require a permit review, a permeable surface or on-site stormwater management.
Where do these terms come from?
Most come from industry installation guides, such as those published by paver and wall block manufacturers and the Interlocking Concrete Pavement Institute, and from building codes. When a contractor cites a manufacturer's guide, you can read the same document and check the specified depths and materials yourself.
How can I use the glossary with the rest of this site?
Read the terms before collecting estimates, then use them to fill in the gaps on each proposal. The service pages show each term in context, and the estimate request page lists what to include so bidders price the same scope.
See the terms in context
Service guidePaver Patio InstallationPaver patio installation is the excavation, compacted stone base, bedding layer, laid pavers, edge restraint and joint fill that together create a level, drained outdoor surface.
Service guideRetaining Wall ConstructionRetaining wall construction turns a grade change into stable, usable ground with a footing, a wall of segmental block, stone, timber or poured concrete, and the drainage stone and pipe behind it.
Service guideFire Pit & Fireplace InstallFire pit and fireplace installation covers built-in wood or gas fire pits, masonry or prefabricated outdoor fireplaces, the non-combustible surface around them, gas or electrical lines and the clearances local rules require.
Service guideWalkways & DrivewaysWalkway and driveway work covers paths from the street or driveway to the door, garden paths, and vehicle surfaces in pavers, permeable pavers, concrete or stone.
Service guideOutdoor Living SpacesOutdoor living space planning coordinates patio, seating, cooking, shade, lighting, fire, paths, walls and planting into one plan that can be built at once or in phases.
Free planning tools
Free toolPatio cost calculatorSize, material tier and complexity in, a realistic budget range out.
Free toolCompare hardscape options, row by rowSide-by-side tables for the decisions that change the price most.
Free toolHardscape planning quiz9 questions that show what you already know and what to check next.
Free toolHardscape polls: how other homeowners are decidingSee what other planners chose and add your vote.
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