How-ToUpdated May 2026By TradeMatch Editorial Team·14 February 2026·Updated 12 April 2026·8 min read

How to Prepare for a Loft Conversion: A Step-by-Step Guide

A loft conversion is one of the most cost-effective ways to add space to your home — typically adding 10–20% to your property value. Here is everything you need to know before starting.

Professional tradesperson completing quality work

Types of Loft Conversion

Type	Cost Range	Planning Permission?	Best For
Velux / roof light	£20,000–£35,000	Usually not needed	Budget-friendly, simple lofts
Dormer	£30,000–£50,000	Usually not needed	Most popular, adds headroom
Hip-to-gable	£40,000–£55,000	Usually needed	Semi-detached and detached houses
Mansard	£45,000–£65,000	Usually needed	Terraced houses, maximum space

Step-by-Step Preparation

Step 1: Check feasibility — Your loft needs a minimum head height of 2.2m at the ridge. A loft conversion specialist or structural engineer can assess this.

Step 2: Planning permission — Most loft conversions fall under Permitted Development, but check with your local authority. Party wall agreements may be needed for terraced or semi-detached houses.

Step 3: Get quotes — Get at least 3 detailed quotes from vetted loft conversion specialists on TradeMatch.

Step 4: Agree the design — Work with your specialist on layout, staircase position, window placement and insulation.

Step 5: Building regulations — Your contractor must ensure compliance with Part B (fire safety), Part L (insulation) and Part P (electrics).

Step 6: Timeline — A typical loft conversion takes 6–10 weeks. Plan for some disruption, especially when the staircase is cut in.

Frequently Asked Questions

Do I need planning permission for a loft conversion?

Most loft conversions fall under Permitted Development rights and do not need planning permission, provided they stay within volume limits (40m3 for terraced, 50m3 for detached/semi). Dormers facing a highway and mansard conversions usually require planning permission.

How long does a loft conversion take?

A typical dormer loft conversion takes 6–10 weeks from start to finish. Velux conversions are quicker (4–6 weeks), while mansard conversions can take 8–12 weeks.

Will a loft conversion add value to my home?

Yes. A well-executed loft conversion typically adds 10–20% to your property value. In London, where space is at a premium, the uplift can be even higher, often more than the cost of the conversion itself.