Gray Granite 1.5"

Gray Granite 1.5" — Heavy-Duty Stone for Deep Drainage & Backfill

Also sold as #4 Stone (Crushed Granite) — the contractor spec name for the same material (AASHTO M43 / ASTM D448 No. 4).

Gray Granite 1.5" is the size that drainage installers, septic contractors, and excavators reach for when the project calls for serious water-moving capacity. The larger void space between stones means water flows through fast — critical for French drains, septic system bedding, and any application where the job is to get water out and away.

At a glance

What it's good for

• Deep French drains and footing drains around foundations
• Septic system pipe bedding and trenching
• Storm drain systems and dry-well construction
• Retaining wall backfill behind block and stone walls

How much do I need?

A 100' French drain trench (12" wide × 24" deep) needs about 7.4 cubic yards. Backfilling a 50' segmental retaining wall (12" deep gravel zone behind the block) takes roughly 3.7 yards. Septic pipe bedding sizes are dictated by the engineered design — your installer will give you the exact volume.

How Gray Granite 1.5" compares

• vs. Gray Granite ¾": 1.5" is the deeper-drainage size with bigger voids and faster water flow. ¾" is the driveway standard.
• vs. Rip Rap 6"–12": Rip rap is much larger — used for erosion control along shorelines, ditches, and high-energy stream banks. 1.5" sits below rip rap in scale.
• vs. Crushed Concrete 1" to minus: Crushed concrete is dense-graded with fines for compaction. 1.5" gray granite is clean for drainage. Different jobs.
• vs. Blue-Gray Granite ¾": Different color and smaller size; ¾" is finish gravel, 1.5" is drainage rock.

Frequently asked questions

What is Gray Granite 1.5" used for?
Heavy drainage, foundation backfill, large culvert bedding, septic system stone, and the transition layer between rip rap and finer drainage rock. It is reserved for deeper, higher-flow applications than the ¾" residential standard.

Is Gray Granite 1.5" the same as #4 stone?
Yes — gradationally, 1.5" gray crushed granite meets AASHTO M43 / ASTM D448 No. 4. The residential descriptor and the contractor spec name point to the same material.

Will this stone clog up?
No. Because it's clean of fines, the void space between the stones stays open and water flows freely. Wrap the trench in non-woven filter fabric to keep silt and fines from migrating in from the surrounding soil.

How deep should a French drain be?
For typical residential downspout dispersal, 18–24" deep × 12" wide works. For foundation drains around a full basement, follow the engineer's spec — usually 24"+ deep wrapped in filter fabric at the footing.

How much does a cubic yard of 1.5" gray granite weigh?
About 2,500 lbs per cubic yard, or roughly 1.25 tons.

Do you deliver drainage stone in the Boston area?
Yes — same-day and next-day bulk delivery across Suffolk, Middlesex, Norfolk, and Plymouth Counties.

Same-day and next-day bulk delivery, no minimum order. We run drainage stone routes across Plymouth, Middlesex, Norfolk, and Suffolk County.

Pair with our gray granite ¾" for the upper drainage layer or driveway top coat above, or our septic sand for Title 5 leach field installations alongside.

Order today — the heavy-duty drainage stone for jobs that need real flow capacity.

• Same-day & next-day delivery available — weekends fill fast, order early.
• Curbside or on-property drop — let us know at checkout.
• Up to 6 yds per load for dense materials (gravel, soil, rock, sand) — mulch loads carry up to 10 yds. $100 flat rate, no minimum order.
• Job site delivery available — live load tickets and signed BOLs on request.
• Questions? Call (617) 645-0987 or see full delivery info →