Last checked
May 12, 2026
We checked the page logic, support notes, and related links on this page.
Small-roof felt tool
Shed Felt Calculator
Estimate shed felt rolls and rough cost for sheds, summerhouses, and small outbuildings.
Area + buying unitsWaste-aware resultBuying checks
How to use it
Planning before buying
Use this calculator for a planning check, then confirm the final order or quote against live product data and site conditions.
Why trust it
See how the site is maintained
Read the calculator methodology and editorial policy for the standards behind these pages.
Planning summary
Quick answer
Measure each roof slope, add overlap and edge waste, then round up to full felt rolls for the shed or garden building.
Planning summary
Watch most
Common issues include ignoring overlap, failing to allow for cuts at edges and ridges, and treating every roof as if it behaves like a simple rectangle.
Planning summary
Best next move
Check whether the product is sold by effective coverage after laps or by nominal pack size, because that changes the buying count immediately.
Recently used calculators
Pick up from the calculators you used recently on this device.
Quote-ready brief
Use these actions to turn the live calculator result into a cleaner request for builders, suppliers, or merchants.
Run the calculator, then use these actions to prepare the estimate for a real quote request.
Need help deciding what to ask for? Read the quote checklist or contact the team at hello@buildcostlab.com.
Practical checks before you buy
These notes are where BuildCostLab goes beyond a generic calculator result by surfacing the assumptions, buying traps, and next decisions that usually move the real order.
Global terminology and buying units
Use this page across English-speaking markets by matching the local material name, unit, and buying format.
Also known as
shed roof felt calculatorsmall roof felt calculatorgarden building roofing calculator
Search intent
shed felt calculatorshed roof felt calculatorshed roofing felt calculator
Quick answer
Measure each roof slope, add overlap and edge waste, then round up to full felt rolls for the shed or garden building.
Regional buying note
For sheds and outbuildings, roll coverage changes quickly once side laps, ridge laps, drips, and damaged edges are included.
Unit examples
Use m2 or sq ft for roof area, then compare rolls by installed coverage after overlap rather than nominal roll coverage.
What this estimate includes
The measured coverage area, stated product yield or pack coverage, waste allowance, whole-unit rounding, and a rough material spend when a price is entered.
What it may not include
Live product instructions, substrate preparation, delivery charges, labour, and installation details that depend on the specific product system.
Key assumptions
Roofing estimates rely on covered area, lap or overlap allowances, and the fact that roof shape and pitch often increase the real material take-off above a simple plan area.
Worked example
Example: 12m2 of measured coverage with 10 percent waste becomes 13.2m2 of planned coverage. Divide by the real pack or unit yield, then round up to the next full buying unit.
How this estimate is worked out
We multiply length by width, add the waste allowance, then convert the adjusted area into whole buying units using the stated coverage per pack, roll, sheet, bag, or tin.
What assumptions sit underneath it
Roofing estimates rely on covered area, lap or overlap allowances, and the fact that roof shape and pitch often increase the real material take-off above a simple plan area.
How rounding is handled
Because most products are bought in full packs, rolls, sheets, or tins, the final answer rounds up to a real ordering total rather than stopping at the theoretical minimum.
What changes the result most
Real product yield, waste, awkward cuts, surface condition, and whole-pack rounding usually move the final order more than people expect.
When this estimate breaks
Remeasure when the product coverage is uncertain, the layout is heavily cut up, or the supplier sells in pack sizes that do not match the default assumptions.
Practical buying checks
Check batch matching, spare stock, delivery timing, and whether running short would be more expensive than buying one extra unit.
Quote-ready checklist
Use these prompts when you want to turn the estimate into a clearer builder, installer, or merchant request.
- State the measured area, product choice, waste allowance, and how the material is sold.
- Ask the supplier or installer to confirm real coverage and whether substrate condition changes the quantity.
- Check whether one spare unit is sensible for matching, touch-ups, awkward cuts, or batch consistency.
Explore this project hub
Open the full Roofing Estimating project hub to move from quick estimate to deeper guidance.
Related calculators in the same project hub
Use these linked tools when the estimate crosses into another calculator in the Roofing Estimating cluster rather than stopping at one isolated material number.
Roof Felt Calculator
Estimate roof felt rolls and rough cost for sheds, garages, and outbuildings.
Roofing Shingle Calculator
Estimate roofing shingle bundles and rough cost from roof coverage area.
Roof Batten Calculator
Estimate batten lengths, pieces, and rough cost for roof work.
Keep planning the same job
These are the strongest next calculators when this estimate is only one part of the buying or quote-prep workflow.
Next stepRoofing
Roof Felt Calculator
Estimate roof felt rolls and rough cost for sheds, garages, and outbuildings.
Next stepRoofing
Roof Batten Calculator
Estimate batten lengths, pieces, and rough cost for roof work.
Next stepRoofline
Gutter Calculator
Estimate gutter lengths, stock pieces, joints, waste allowance, and rough material cost for simple roofline runs.
Next stepExterior finishes
Wood Stain Calculator
Estimate wood stain quantities and rough cost for fences, cladding, sheds, and exterior timber.
Quick answers
These answers are designed to resolve the last practical buying questions people usually have after running the calculator.
How do I use the Shed Felt Calculator?
Enter the covered dimensions, choose a realistic waste setting, and use this calculator to turn the measured area into a practical buying quantity.
What changes the Shed Felt Calculator estimate most?
The biggest drivers are the measured area, the waste allowance, and the coverage rate or unit count used to turn that area into a buying quantity.
Should I round the result up?
Roofing jobs rarely reward under-ordering. A small overage is usually cheaper than the disruption caused by a short finish course or delayed extra delivery.
Use this estimate in a quote request
Copy the estimate, add your own notes, and send the same scope to each builder or supplier so the quotes are easier to compare.
- Confirm what the quote should include: materials only, labour only, or both.
- State access, finish level, timing, and any unknowns clearly.
- Ask each supplier or installer to price the same scope and exclusions.
You can also open the wider Roofing Estimating project hub if the quote depends on more than one material.