Bespoke Design & Planning

Over 12 Years of Experience

Free Consultation & Itemised Quotes

Full Cost Transparency & Project Management

Insurance Backed Warranty

The shape that makes it possible

You can never have enough living space; more is always better. A growing family, a missing amenity, or simply to make your house a lucrative option to buyers drive homeowners to look for additional space in their own homes. If you love your home, chances are you would hate to move just for bigger space. While the price of moving to a bigger floor space can be hefty, it can also cause emotional distress, and interference with work, children’s schools, and neighbourhood ties. It is where we come in with the game-changing L-shaped dormer.

It is the magic letter that makes the difference. An L-shaped loft conversion is constructed by connecting two dormers at a right angle to each other, forming an L shape. While the larger dormer sits on the main roof, the smaller section stands on the rear roof. The new roof is almost flat, but a 1:50 fall to the side creates rainwater drainage. A small-scale border is built around the perimeter of the construction to tone down the bulkiness of the structure by softening the sharpness of its features. It allows the existing roof slope to blend in with the new addition.

You get more than double the space that comes with a single dormer. L-shaped extensions can generate several rooms or two generous sized rooms. A decent-sized master bedroom with en suite bathroom can fit in the new space comfortably. You can achieve plenty of natural light with this type of loft conversion.

Victorian and Edwardian semi-detached and terraced homes are best suited for this extension. Often Victorian properties have the kitchen and bathroom situated at the rear of the property, making the rear extension easier to perform.

Generally, no permission is required, as these are permitted development rights. However, there are exceptions and requirements, and they change from one local council to another. Listed buildings and conservation areas are exceptions to the permitted development rules, and you need to get council permission. The same is required if the size of the conversion exceeds 40 cubic metres for terraced homes and 50 cubic metres for other properties.

A certificate of Lawfulness enables you to perform necessary construction within building guidelines. Good Design & Build submits applications for legal requisites as we have record success. You will also need to obtain party wall agreements from neighbours. We assist in these during the pre-build stage, where all necessary processes that pave the way for clearance to build get completed.

The cost varies as it can differ from one loft conversion to another. While some designs are more intricate, others are more straightforward. The average cost for an L-shaped conversion is £45,000. We maintain transparency throughout the process and will inform you of the total estimated cost when we visit your home for a free itemised quote.

  • A 2.2m of head height is essential not just as a regulation but to make your loft functional.
  • Your new floor should have sufficient structural strength.
  • The existing roof should not be in any sort of danger of collapse or damage.
  • The new floor joists should provide at least 30mins of fire protection.
  • The conversion should feature a safely designed staircase of 2m minimum height above the pitch line with a maximum amount of 16 stairs.
  • Sufficient insulation between the conversion and the room below is necessary.

Our structural engineers can help you decide the best ways to construct within regulation. Good Design & Build has a hands-on approach to work and offers each project team dedication and equal passion. We manage the whole project from day 1 to the very last, reducing your responsibilities considerably. Try our free consultation today.

How we deliver projects

Our process is simple and divided into two distinct phases with separate contracts: Design and Build. As a client you only commit to one phase at a time depending on what stage of the process you are in. Each phase consists of three stages as described below.

1. Design

This is the kick-off point for your project. We carry out a complete architectural measured survey of the property. This allows us to create accurate CAD design drawings. This is followed by a design meeting to start discussing your ideas in more detail.

2. Planning

At this stage we finalise the designs with you and start preparing planning applications as needed. We place a high priority on ensuring that plans, designs and schedules are all based on a thorough and detailed understanding of planning guidelines. We co-ordinate with local authorities until the decision is made, and the planning approval is secured.

3. Technical

Once the planning consent is secured, we translate the design drawings into more detailed technical drawings for the purposes of building control and construction. This also includes specifications and structural calculations. At this stage, we will also submit to you our ‘no obligation’ quote for the build phase.

4. Pre-build

90% of our clients decide to stick with us after the design phase is completed. Once the build contract is signed, we kick off the process by making sure all the pre-build processes are complete. These include assistance with party wall agreements, Thames Water build over agreement, submitting building control application, and preparing method statements etc as needed. This stage ends with a pre-start meeting with your foreman before the actual build begins.

5. Build

One of our foremen will be dedicated to your project and will be on-site to manage everyday works. Our project managers will be overseeing the works to make sure they are completed to high standards, within your budget and on time. Throughout the process we will keep you updated with the progress and coordinate the works with third parties such as kitchen or flooring suppliers. We will also advise and guide you to choose any suppliers if needed.

6. Handover

As the build draws to finish, we will help to iron out any ‘snags’ to make sure everything is completed to your satisfaction. We will put together all necessary certificates such as gas, electricity and building control completion along with warranties for glazing, boiler etc. At the final completion meeting, we will hand you these documents, together with the keys to your house. Needless to say, you can contact us any time after this, if you want us to look at something.


This is the kick-off point for your project. We carry out a complete architectural measured survey of the property. This allows us to create accurate CAD design drawings. This is followed by a design meeting to start discussing your ideas in more detail.

At this stage we finalise the designs with you and start preparing planning applications as needed. We place a high priority on ensuring that plans, designs and schedules are all based on a thorough and detailed understanding of planning guidelines. We co-ordinate with local authorities until the decision is made, and the planning approval is secured.

Once the planning consent is secured, we translate the design drawings into more detailed technical drawings for the purposes of building control and construction. This also includes specifications and structural calculations. At this stage, we will also submit to you our ‘no obligation’ quote for the build phase.

90% of our clients decide to stick with us after the design phase is completed. Once the build contract is signed, we kick off the process by making sure all the pre-build processes are complete. These include assistance with party wall agreements, Thames Water build over agreement, submitting building control application, and preparing method statements etc as needed. This stage ends with a pre-start meeting with your foreman before the actual build begins.

One of our foremen will be dedicated to your project and will be on-site to manage everyday works. Our project managers will be overseeing the works to make sure they are completed to high standards, within your budget and on time. Throughout the process we will keep you updated with the progress and coordinate the works with third parties such as kitchen or flooring suppliers. We will also advise and guide you to choose any suppliers if needed.

As the build draws to finish, we will help to iron out any ‘snags’ to make sure everything is completed to your satisfaction. We will put together all necessary certificates such as gas, electricity and building control completion along with warranties for glazing, boiler etc. At the final completion meeting, we will hand you these documents, together with the keys to your house. Needless to say, you can contact us any time after this, if you want us to look at something.

What Our Clients Say

Featured Projects

Build a Quote!

Let's get started with building your own bespoke quote for your dream extension. Tell us as much in detail as possible to get most accurate price.

Get Started

Build a Quote!

Let's get started with building your own bespoke quote for your dream extension. Tell us as much in detail as possible to get most accurate price.

Get Started