Building an Extension Calculators

Scaffolding Calculator

Scaffolding requirements and hire costs for the build.

Skip Size Guide

Choose the right skip size for construction waste.

Van Payload Calculator

Check your van can carry the material weights involved.

Foundation Calculator

Foundation depth, width and concrete volume for strip or trench fill.

Concrete Volume Calculator

Concrete volume for foundations, oversite slab and paths.

Concrete Mix Calculator

Cement, sand and aggregate quantities for site-mixed concrete.

Rebar Calculator

Reinforcement bar quantities for reinforced foundations.

Lintel Sizing Calculator

Correct lintel sizes for window and door openings.

Padstone Sizing Calculator

Padstone dimensions for steel beam bearings.

Brick Calculator

Facing bricks for the outer leaf of cavity walls.

Block Calculator

Concrete blocks for the inner leaf and below-ground work.

Mortar Calculator

Sand and cement for bricklaying and blockwork mortar.

Roof Area Calculator

Calculate actual roof area from plan dimensions and pitch.

Roof Tile Calculator

Tile quantities for pitched roof extensions.

Felt and Batten Calculator

Roofing felt and batten quantities.

Ridge Tile Calculator

Ridge tiles and mortar for the roof ridge.

Soffit and Fascia Calculator

Soffit boards and fascia lengths.

Gutter Sizing Calculator

Gutters and downpipes for the extension roof.

Lead Flashing Calculator

Lead flashing for abutments where the extension meets the house.

Flat Roof Membrane Calculator

Membrane and insulation for flat roof extensions.

U-Value Calculator

Check wall, floor and roof U-values meet Part L.

Insulation Thickness Calculator

Determine insulation depth for walls, floors and roof.

Cavity Wall Insulation Calculator

Cavity wall insulation quantities for the new walls.

Heat Loss Calculator

Heat loss for the new rooms to size the heating system.

Cable Sizing Calculator

Cable sizes for new circuits from the consumer unit.

Socket Spacing Calculator

Plan socket layouts for the new rooms.

Lighting Layout Calculator

Lighting positions and lux levels.

Maximum Demand Calculator

Check your supply can handle the additional load.

Radiator Sizing Calculator

BTU output needed for new rooms.

Boiler Size Calculator

Check your boiler capacity for the additional rooms.

Underfloor Heating Pipe Calculator

Pipe lengths if installing wet underfloor heating.

Pipe Sizing Calculator

Pipe sizes for hot and cold water supply extensions.

Plasterboard Calculator

Plasterboard for walls and ceilings in the new rooms.

Plaster Coverage Calculator

Plaster bags needed for bonding and skimming.

Skim Coat Calculator

Multi-finish for skim coating all surfaces.

Paint Coverage Calculator

Paint quantities for decorating the new rooms.

Screed Calculator

Screed volume for the extension floor.

Floor Tile Calculator

Floor tiling quantities if tiling the new rooms.

Laminate Flooring Calculator

Laminate or engineered wood flooring packs.

Skirting Board Calculator

Skirting board lengths and mitre cuts.

Soakaway Sizing Calculator

Size a soakaway for the extension roof drainage.

Drainage Fall Calculator

Correct gradient for foul and surface water drains.

Type 1 Sub-Base Calculator

Sub-base material for oversite preparation.