Loft Conversions in Hertfordshire and the Home Counties
The fastest way to add a bedroom and bathroom without moving. Designed, approved and built by one team, usually in 8 to 12 weeks on site.
Federation of Master Builders
30+ Years · 100+ Projects
Hertfordshire and Home Counties
Master Builder of the Year
The Best Room in the House Is Currently Full of Boxes
A loft conversion is usually the quickest, least disruptive way to add real space: a master suite with views, a bedroom for a growing family, or a quiet office at the top of the house. Most of the work happens from outside, so daily life carries on below while the new floor takes shape above.
Done properly, it is also one of the strongest value-adding projects in this part of the country. At Mosaic Bespoke the key is design and structure: head heights, stairs, light and insulation all decided correctly at the start, not patched later.
Costs, timing and planning, answered up front.
What It Costs
As a guide, a quality dormer loft conversion typically costs between £50,000 and £85,000 including a bathroom, with hip-to-gable and mansard conversions above that. The calculator below shapes a figure to your roof and specification.
Planning Permission
Many loft conversions fall under permitted development, including most rear dormers, subject to volume limits. Front-facing changes and some settings need consent. We confirm the position and handle any application.
How Long It Takes
Most loft conversions take 8 to 12 weeks on site once design and approvals are in place. Because we work largely from scaffold outside, disruption inside the house is kept to a minimum until the staircase goes in.
Why Convert the Loft?
It is the fastest, least disruptive space you can add: weeks on site rather than months, with the family living normally below for most of the build.
An extra bedroom and bathroom moves a home up a bracket, and loft space consistently ranks among the best returns of any home improvement in this area.
Because most lofts convert under permitted development, many projects can start without a full planning application at all.
Our Process.
Every project follows the same four-stage process, structured to provide clarity, manage planning risk, and ensure your loft conversion is comprehensively prepared before construction begins.
01
Discover
Opinion of Probable Cost
Understand what your loft conversion is likely to cost before committing further.
02
Define
Feasibility Study
Assess planning risk, structure and budget exposure specific to your home.
03
Prepare
Pre-Construction Agreement
Coordinate design, engineering and cost control before your loft conversion begins on site.
04
Deliver
Construction and Delivery
Build with one accountable, structured team, managed daily from start to handover.
See what your loft conversion could cost
What type of extension are you planning?
Choose the option closest to your project.
Answer a few quick questions for an instant guide figure. The estimate is based on typical local build costs; for a detailed figure we will arrange a free consultation.
Frequently Asked Questions
How much does a loft conversion cost?
As a guide, a dormer conversion with a bathroom typically comes out between £50,000 and £85,000, depending on size, structure and finish. Hip-to-gable and mansard conversions cost more. Use the calculator above for a guide figure.
Do I need planning permission for a loft conversion?
Often not. Many lofts convert under permitted development, particularly rear dormers within volume limits. Conversions that change the front of the roof, and homes in some protected settings, need consent. We check and confirm for you.
Is my loft high enough to convert?
As a rule of thumb you want around 2.2 metres from the top of the existing ceiling joists to the ridge. Below that, options still exist but the design has to work harder. We measure and advise honestly at the first visit.
Can we stay in the house during the work?
Almost always, yes. The structure is built from outside via scaffold, and the connection through to the house is one of the last steps. Most families barely change their routine until the staircase is fitted.
Will I need a party wall agreement?
If you live in a semi-detached or terraced house, usually yes, as the new structure bears on or near the shared wall. We prepare and serve the notices as part of the project.
Considering a Loft Conversion?
If you are wondering what your roof could become, our appraisal covers head heights, structure, planning and budget, honestly and without obligation.
Loft conversions across Hertfordshire and the Home Counties
We build loft conversions from our base in St Albans and across Harpenden, Radlett, Potters Bar, Hemel Hempstead and Berkhamsted, and throughout Hertfordshire, Essex and the southern counties. Exploring your options? See our house extensions page, or compare with barn conversions, double storey extensions and wrap-around extensions.