50 Specialist Calculators
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Professional tools for serious builders

A garage conversion is one of the most cost-effective ways to add usable living space to a property. Converting an integral or attached garage typically costs a fraction of a full extension yet delivers a full habitable room - home office, bedroom, playroom or utility space - that adds meaningful value and function to the home.

The range of trades involved makes garage conversions more complex to plan than they first appear. The floor needs damp-proofing, insulating and screeding to bring it up to habitable standard. The walls need framing, boarding, plastering and decorating. The garage door opening is usually replaced with a stud wall section, new window and door. Getting the sequence right and the material quantities accurate at each stage is what separates a smooth conversion from an expensive one.

This kit covers every stage from groundworks through to final decoration: damp proof membrane for the floor, floor and wall insulation to meet Part L, concrete screed, stud wall framing, plasterboard for walls and ceiling, skim plaster for any masonry walls, interior paint, and skirting board around the finished room perimeter.

What this kit covers

Work through these 8 calculators in order. Each one uses your garage dimensions to pre-fill the key inputs - just refine the details and save each result to your project.

1
Damp Proof Membrane
Calculate DPM sheet to cover the existing concrete floor before insulation and screed - essential to prevent rising damp.
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2
Insulation Calculator
Work out floor, wall and ceiling insulation quantities to bring the garage up to habitable thermal standards (Part L).
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3
Concrete Screed
Calculate sand and cement screed to level and finish the floor over the insulation layer.
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4
Stud Wall Calculator
Work out timber stud quantities for any new partition walls, including the front wall if replacing the garage door opening.
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5
Plasterboard Calculator
Calculate plasterboard sheets for all walls and ceiling, including screws, jointing tape and finishing compound.
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6
Render & Plaster
If skimming over existing masonry walls, calculate scratch coat and finish plaster quantities.
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7
Interior Paint
Calculate emulsion and ceiling paint for the finished interior walls and ceiling.
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8
Skirting Board Calculator
Calculate linear metres of skirting board for the room perimeter once all floor and wall finishes are in place.
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Start this project

Enter your garage dimensions and we'll create a project with pre-filled starting points for each calculator.

External doors in the converted space
Typically 65mm over insulation

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