Calculator Inputs
Use conservative loads when the shed will store heavy equipment, dense materials, or seasonal items.
Formula used
The calculator converts metric dimensions to feet when needed. It then applies these planning formulas:
- Floor area = length × width.
- Floor dead load = floor thickness ÷ 12 × material density.
- Base dead load = base depth ÷ 12 × base density.
- Total service load = area × (dead load + live load + roof load) + storage + occupants + equipment.
- Effective contact area = floor area × contact percent ÷ 100.
- Ground pressure = total service load ÷ effective contact area.
- Adjusted soil bearing = allowable soil bearing × soil condition factor.
- Safety factor = adjusted soil bearing ÷ ground pressure.
- Point pressure = local point load ÷ point pad area.
How to use this calculator
- Enter shed length and width at the supported base.
- Pick the closest floor type. Adjust thickness and density.
- Add gravel, stone, or base depth if it supports the shed.
- Enter live load, stored weight, people allowance, and equipment weight.
- Set contact percent. Use 100 for a full slab. Use less for skids.
- Enter soil bearing capacity and reduce it for wet or soft ground.
- Press the calculate button. Review pressure, safety factor, and point load checks.
- Download the CSV or print the result for project records.
Example data table
| Example shed | Area | Floor setup | Live load | Soil bearing | Use case |
|---|---|---|---|---|---|
| 8 ft × 10 ft | 80 sq ft | Wood sleepers on stone | 30 psf | 1,500 psf | Garden tools |
| 10 ft × 12 ft | 120 sq ft | 4 in slab with gravel | 40 psf | 1,500 psf | Mower storage |
| 12 ft × 16 ft | 192 sq ft | Reinforced pad | 60 psf | 2,000 psf | Workshop storage |
Ground Supported Shed Floor Planning
A shed placed on ground still needs a load check. The floor may look simple. Yet the soil carries every pound. Weak soil can settle. Mowers, bins, and tools add pressure quickly.
Why contact area matters
This calculator estimates service load over the shed footprint. It also checks effective ground contact. Some sheds touch ground with full pads. Others rest on skids, sleepers, or small bearing strips. Less contact area means higher soil pressure.
Load inputs
Start with accurate outside dimensions. Measure length and width at the supported base. Enter floor thickness, density, and base depth. A concrete slab usually weighs more than a framed wood floor. Gravel also adds dead load. Walls and roof loads can be entered as an added allowance.
Live load covers people and movable storage. Use a higher value for workshops, motorcycles, lawn tractors, or dense shelving. Add known equipment weights separately. Roof snow or roof storage can also be included. The tool spreads these loads across the floor area.
Soil bearing checks
The soil bearing input is important. Firm gravel and compacted granular soil support more load. Soft clay, wet fill, and organic soil support less. The condition factor reduces the listed soil value. It helps reflect field risk. It is still only an estimate.
Ground pressure should stay below adjusted bearing capacity. A stronger result also needs a practical safety factor. The calculator shows total weight, pressure, factored pressure, and safety margin. It also checks a local point load from a jack stand, wheel, or leg pad.
Better base choices
Use the results for planning the base. If pressure is high, increase contact area. Add wider skids, thicker pads, compacted stone, or a reinforced slab. Improve drainage before placing the shed. Water weakens support and causes frost movement in cold areas.
This tool does not replace local code or engineering advice. Large sheds need permit checks. So do structures with vehicles, living space, or unusual loads. Use conservative inputs when conditions are unknown. A small design change can prevent long term settlement.
Record assumptions with each estimate. Future owners can see why the base was selected. Recheck loads after adding large machines, stacked lumber, batteries, or water tanks. Small sheds often become heavier over time. Plan drainage early.
Frequently Asked Questions
What does shed ground floor load mean?
It is the weight from the shed, floor, base, storage, people, and equipment divided by the area that actually bears on the ground.
Should I use the full floor area?
Use the full area only when the whole base contacts the ground. Use a lower contact percent for skids, runners, pads, or narrow bearing strips.
What live load should I enter?
Light garden storage may use a modest value. Workshops, mowers, motorcycles, and stacked supplies need higher values. Use conservative inputs when unsure.
Does gravel count as load?
Yes. A gravel base has weight. Enter its depth and density so the calculator includes that load in the ground pressure result.
What is the soil condition factor?
It reduces the listed soil bearing capacity for risk. Wet soil, loose fill, organic soil, or soft clay should use a lower factor.
Why is point load checked separately?
A wheel, jack, machine foot, or shelf leg can press on a small area. That local pressure may be critical even when total pressure is acceptable.
Can this replace a permit design?
No. It is a planning calculator. Check local code, manufacturer instructions, soil conditions, and engineering advice for larger or critical sheds.
What if the result fails?
Increase bearing area, improve compaction, add a stone base, use wider skids, reduce storage weight, or ask a professional to review the foundation.
Can I use meters for dimensions?
Yes. Select meters for length and width. Other load inputs remain in inch, pound, psf, and pcf units for simple construction entry.
Why include roof or snow load?
Roof and snow loads travel through the shed walls or frame into the base. Adding them gives a safer ground pressure estimate.
How do I save my result?
After calculation, use the CSV button for spreadsheet records. Use the print button to create a paper copy or saved PDF.