SettingsSettings for this calculationUS
The installed depth of the growing medium layer.
Measure the depth of the growing medium itself, not the overall green roof assembly (which also includes drainage, filter fabric, and root barrier layers).
The total plan area of the green roof covered by growing medium.
Use the plan (horizontal) area of the green roof system, not the roof's sloped surface area.
The fully saturated (water-holding capacity) density of the specific growing medium product.
Lightweight engineered green roof media commonly range roughly 800-1,600 kg/m³ when fully saturated, versus native soil which can be much heavier — always use the exact value from the medium manufacturer's data sheet, not an assumed default.
Total saturated growing medium weight
40,500 lb
Saturated density is specific to the growing medium product used — always use the exact value from the manufacturer's data sheet, not an assumed default. This calculates the load QUANTITY only; the roof structure's actual capacity to carry this additional dead load (on top of the existing roof assembly, snow load, and live load) must be verified by a qualified structural engineer before installing a green roof.
- Load per unit area
- 37.47 psf
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Green Roof Growing Medium Saturated Load Calculator: 40,453 lb — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Total saturated weight = Medium Depth × Roof Area × Saturated Density; Load per unit area (kPa) = Medium Depth × Saturated Density × 9.81 ÷ 1000. Saturated growing medium density is product-specific (lightweight engineered green roof media commonly range roughly 800-1,600 kg/m³ when fully saturated, versus native soil which can be much heavier) — this calculator applies the density you supply from the specific medium manufacturer's data sheet. This is a load QUANTITY calculation only — the roof structure's capacity to carry this load must be verified by a qualified structural engineer.
Inputs used
- Growing Medium Depth
- 6 in
- Green Roof Area
- 1080 sq ft
- Saturated Growing Medium Density
- 74.91 pcf
Intermediate steps
- Load per unit area
- 37.47 psf
Confidence note: Saturated density is specific to the growing medium product used — always use the exact value from the manufacturer's data sheet, not an assumed default. This calculates the load QUANTITY only; the roof structure's actual capacity to carry this additional dead load (on top of the existing roof assembly, snow load, and live load) must be verified by a qualified structural engineer before installing a green roof.
What this calculation does not cover
- The medium alone, and it is not the whole roof. Drainage or reservoir board holding its own water, the filter fleece, protection mat and root barrier, the plants at maturity, and on an intensive build-up the pavers, edgings, planters, deeper soil in beds and any irrigation all bear on the same deck and none of them are in this figure. On a lightweight extensive roof the balance of the assembly commonly adds tens of kilograms per square metre over the media; on an intensive one it can exceed the media outright.
- The load per unit area above is an average, and a green roof is deliberately not loaded evenly. Mounded beds, the deeper substrate that usually runs along the parapet, a gravel border, paved access routes and any cluster of large plants or seating concentrate weight over particular bays, while the structure is checked at the worst bay rather than at the mean. A comfortable average can sit directly over a beam that is not comfortable at all.
- Saturated is the free-draining maximum, not the worst case. Saturated density is measured with the water the media retains after it has drained; if an outlet blocks or the drainage layer silts up, water ponds above the substrate and every 10 mm (0.39 in) of standing water adds another 10 kg (22 lb) per square metre with nothing to arrest it. The blocked-outlet condition, and an overflow that still works when the primary drain does not, is what keeps that case from being open-ended.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- Total saturated weight = Medium Depth × Roof Area × Saturated Density; Load per unit area (kPa) = Medium Depth × Saturated Density × 9.81 ÷ 1000. Saturated growing medium density is product-specific (lightweight engineered green roof media commonly range roughly 800-1,600 kg/m³ when fully saturated, versus native soil which can be much heavier) — this calculator applies the density you supply from the specific medium manufacturer's data sheet. This is a load QUANTITY calculation only — the roof structure's capacity to carry this load must be verified by a qualified structural engineer.
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