The Overall Timeline at a Glance

In broad terms, a loft conversion typically takes:

• 3 to 6 months from initial planning to completion

• 8 to 12 weeks for on-site construction alone

More complex conversions, such as mansard lofts or projects requiring planning permission and party wall agreements, can extend beyond this timeframe. Simpler conversions may be completed more quickly, but even these still involve several distinct stages.

Stage One: Initial Assessment and Feasibility (1–2 Weeks)

The process begins with determining whether a loft conversion is possible. Not all lofts are suitable, and this stage is crucial in avoiding costly surprises later on.

A professional assessment will look at:

• Head height (typically a minimum of 2.2 metres is required)

• Roof structure (traditional cut roofs are easier to convert than trussed roofs)

• Available floor space

• Position of the staircase

• Load-bearing capacity of existing walls

During this stage, homeowners usually discuss how the space will be used, whether for a bedroom, office, bathroom or multiple rooms. These decisions influence the complexity of the project and the time required.

If major structural alterations are needed, feasibility may take longer as engineers become involved.

Stage Two: Design and Drawings (2–4 Weeks)

Once feasibility is confirmed, the design phase begins. Architectural drawings are produced to show the layout, structural elements, windows, staircases and any plumbing or electrical installations.

This stage is often underestimated but plays a major role in the overall timeline. Detailed and accurate drawings reduce the risk of changes during construction, which are one of the most common causes of delays.

Structural engineers may also be involved at this point to calculate load requirements and steel beam specifications.

Stage Three: Planning Permission (Up to 8 Weeks, If Required)

Many loft conversions in the UK fall under permitted development, meaning planning permission is not required. However, this depends on factors such as roof alterations, property location and volume limits.

If planning permission is needed, the local authority typically has up to eight weeks to make a decision. This period can feel lengthy, but it is unavoidable where planning rules apply.

Homes in conservation areas, listed buildings and flats are more likely to require permission, which can extend the overall project timeline.

Stage Four: Building Regulations Approval (2–4 Weeks)

Regardless of planning permission, building regulations approval is mandatory for all loft conversions. This ensures the work meets safety standards covering:

• Structural integrity

• Fire safety and escape routes

• Insulation and energy efficiency

• Staircase design

• Electrical and plumbing safety

Approval can be obtained either through the local authority or an approved private inspector. Many homeowners choose to handle this alongside the planning stage to avoid unnecessary delays.

Stage Five: Party Wall Agreements (2–8 Weeks, If Applicable)

For terraced and semi-detached houses, a party wall agreement may be required if the work affects shared walls or structures.

This legal process involves notifying neighbours and, in some cases, appointing surveyors. If neighbours agree quickly, this stage can be relatively fast. However, disputes or delays in responses can extend the timeline significantly.

Experts advise starting the party wall process as early as possible, as it can run in parallel with planning and design.

Stage Six: Pre-Construction Preparation (1–2 Weeks)

Before construction begins, scaffolding is erected, materials are ordered and access arrangements are finalised. This stage is often overlooked, but delays here can push back the entire schedule.

Good contractors plan this phase carefully to ensure work starts on time and runs efficiently.

Stage Seven: Structural Work and Construction (6–10 Weeks)

The construction phase is the most visible part of the project and usually the longest.

Early work focuses on:

• Strengthening the existing floor

• Installing steel beams

• Modifying the roof structure

• Constructing dormers or roof extensions if required

One advantage of loft conversions is that much of this work can be carried out from outside the property, minimising disruption to daily life.

Dormer, hip-to-gable and mansard conversions generally take longer than Velux conversions due to the scale of structural changes involved.

Stage Eight: First Fix (2–3 Weeks)

Once the main structure is complete, the project moves into the first fix stage. This includes:

• Electrical wiring

• Plumbing

• Insulation

• Installation of staircases

• Fitting windows and roof lights

At this stage, the space begins to take shape, but it is still far from finished. Delays can occur if bespoke components, such as staircases or windows, are not delivered on time.

Stage Nine: Plastering and Second Fix (2–4 Weeks)

Plastering marks a major milestone, transforming the loft into a recognisable living space. After plastering, the second fix stage begins, which includes:

• Fitting sockets and lighting

• Installing radiators and bathroom fittings

• Joinery and built-in storage

• Flooring and decoration

This phase often takes longer than expected, particularly if high-end finishes or custom features are involved.

Stage Ten: Inspections and Completion (1–2 Weeks)

Final building control inspections are carried out to ensure the work complies with regulations. Any issues identified must be addressed before the project is signed off.

Once approved, the loft conversion is officially complete and ready for use.

Factors That Can Extend the Timeline

While many loft conversions run smoothly, several factors can cause delays:

• Planning permission refusals or amendments

• Party wall disputes

• Design changes during construction

• Poor weather conditions

• Supply chain issues

• Shortage of skilled trades

Clear communication and experienced project management can help mitigate many of these risks.

Typical Loft Conversion Times by Type

• Velux loft conversion: 6–8 weeks construction, 3–4 months total

• Dormer loft conversion: 8–10 weeks construction, 4–6 months total

• Hip-to-gable conversion: 10–12 weeks construction, 5–6 months total

• Mansard loft conversion: 12+ weeks construction, 6+ months total

Planning for a Smooth Project

Industry professionals recommend building contingency time into the schedule and finalising design decisions before construction begins. Homeowners who rush the planning stage often face delays later.

Choosing an experienced loft conversion specialist, rather than coordinating multiple trades independently, can also significantly reduce project length and disruption.

A Realistic Expectation

While a loft conversion is not a quick fix, it is one of the most efficient ways to gain additional living space. With careful planning, realistic expectations and professional guidance, most homeowners can expect their loft conversion to be completed within six months from start to finish.

For many, the temporary disruption is a small price to pay for the long-term benefits of extra space, improved functionality and increased property value.