Planning & Building Regulations

Guidance on planning permission and building regulations for home improvement projects in London and Hertfordshire. Permitted development rights, conservation areas, lawful development certificates and building control explained. Written by LCCL Construction, LABC Award Winners 2024.

Single-storey rear extension with glazed doors opening onto a landscaped garden, built by LCCL Construction in Finchley N3

The 6 m and 8 m Rear Extension Without Planning Permission: Prior Approval Explained

Permitted development normally stops at 3 or 4 metres. The larger home extension rules take a single-storey rear extension to 6 metres on a terrace or semi and 8 metres on a detached house, through a 42-day prior approval notification instead of a planning application. Here is how the route works, what the council checks, and what the bigger room costs.

LCCL Construction

1 day ago7 min read

Building regulations drawings for a London house extension laid out ready to price

Already Have Drawings? How We Give You a Fixed Price in 7 Working Days

A lot of London homeowners arrive at the build stage with the design already done: an architect's drawings, an engineer's calculations, a planning decision or Lawful Development Certificate, sometimes party wall awards too. What they need is a builder who will price exactly what is drawn, fix that price, and start. Here is what to send us, who stays responsible for what, how the fixed price is built, and why a job that is ready now can be on site within weeks.

LCCL Construction

Oct 165 min read

Build Small and Certain: Fixed-Price Permitted Development Lofts from £32,400 and Extensions from £42,000

Borrowing is expensive and nobody wants a project that stalls at the planning stage, so this autumn we are putting our weight behind the jobs that carry the least risk: lofts and extensions built under permitted development. No planning application, a Lawful Development Certificate as part of the job, a fixed price for the scope on the drawings, and six to twelve weeks on site. Here are the eight products, the prices, and the five checks that tell you whether your house quali

LCCL Construction

Oct 165 min read

Attached single garage on a 1930s semi-detached house in North London before conversion into a room

Garage Conversion London 2026: Permitted Development, What the Work Involves and the Fixed Price From £21,600

Turning an attached garage into a room is internal work, so on most houses it is permitted development with no planning application. The catch is the parking condition on some newer estates. What a garage actually needs to become a habitable room — floor, walls, roof, the front wall where the door was — how building control checks it, 3–5 weeks on site, and the fixed price at economy specification: from £21,600 inc. VAT (£18,000 + VAT).

LCCL Construction

Oct 166 min read

Rear extension and loft conversion built together on a semi-detached house at Bohun Grove, East Barnet EN4, seen from the garden

Loft Conversion and Rear Extension Together Under Permitted Development: Two Allowances, One Contract, From £98,400

A rear dormer loft and a single-storey rear extension are different classes of permitted development, so the house gets both allowances — the loft's 40 or 50 m³ and the extension's 3 or 4 m depth — in one scheme with no planning application. Why building them together costs less than two projects, how the programme runs, the party wall and certificate sequence, and the combined fixed price at economy specification.

LCCL Construction

Oct 165 min read

Side-return extension on a London Victorian terrace with a glazed roof over the former side alley and sliding doors to the garden

Side Return and Side Extensions Under Permitted Development: The Half-Width Rule, the 4 m Height Limit and the Price

A side-return infill on a Victorian terrace and a single-storey side extension on a semi both sit inside permitted development — as long as the extension is no wider than half the original house and no higher than 4 metres. The rules, the boundary eaves limit, why adding a rear extension to it makes a wraparound that needs planning, and the fixed price.

LCCL Construction

Oct 145 min read

Single-storey rear extension on a London semi-detached house with matching brick, flat roof, roof lantern and aluminium sliding doors

Rear Extension Under Permitted Development in London: 3 m, 4 m or 6–8 m With Prior Approval, and What It Costs

A single-storey rear extension of 3 metres on a terrace or semi, 4 on a detached house, is permitted development — and up to 6 or 8 metres is possible through the prior approval route. The height, eaves, garden and materials rules, what takes a scheme out of PD, the Lawful Development Certificate and the fixed price at economy specification.

LCCL Construction

Oct 145 min read

L-shaped dormer loft conversion over the main roof and outrigger of an Edwardian London terrace, slate-hung cheeks

L-Shaped Dormer Loft Conversion Under Permitted Development: The Terrace Loft That Uses the Whole 40 m³

Victorian and Edwardian terraces with a two-storey back addition can take an L-shaped dormer: one dormer over the main roof, a second over the outrigger, joined at the corner. It uses the 40 cubic-metre terrace allowance to the full and gives two rooms and a bathroom — usually under permitted development with a Lawful Development Certificate.

LCCL Construction

Oct 145 min read

1930s semi-detached house after a hip-to-gable loft conversion, new brick gable matching the original and a rear dormer behind

Hip-to-Gable Loft Conversion Under Permitted Development: The Semi-Detached Loft Without a Planning Application

On a 1930s semi the hipped roof wastes the loft. A hip-to-gable conversion rebuilds the sloping end as a vertical gable, and with a rear dormer it is the loft that gives a semi a full double bedroom and bathroom — almost always under permitted development, with a Lawful Development Certificate and no planning application.

LCCL Construction

Oct 145 min read

Rear dormer loft conversion with slate cheeks on a London Victorian terrace, seen from the garden

Permitted Development Loft Conversion in London: The Rear Dormer You Can Build Without Planning Permission

Most London terraces and semis can take a rear dormer loft conversion under permitted development — no planning application, a Lawful Development Certificate instead, and a fixed price. The 40 and 50 cubic-metre rules, the design limits, what rules a house out, and what it costs at economy specification.

LCCL Construction

Oct 145 min read

1930s semi-detached house in North London with a hipped roof and side garage, for sale board in the front garden

Buying a House to Extend or Convert in London: What to Check Before You Make an Offer

Thinking of buying a house in London because of what you could add to it? The checks to make before you offer — permitted development, loft head height, lease or freehold, drains, trees, party walls — and what the work will cost in 2026.

LCCL Construction

Oct 76 min read

Piggyback loft conversion with the roof raised into a full top storey, original neighbouring roofs for comparison

Piggyback Loft Conversion: What It Is, When It's Allowed and What It Costs

A piggyback loft conversion raises the roof to add a full storey. Why it always needs planning permission, when London councils say yes, the structural work involved and 2026 costs inclusive of VAT.

LCCL Construction

Oct 57 min read

Structural Calculations London 2026: Complete Guide by LABC Award Winners

Do you need structural calculations for your London home project in 2026? Complete guide from LABC Award Winners including when they're needed, typical costs, what's included and LCCL's structural engineering service.

LCCL Construction

Aug 253 min read

House Extension Permitted Development Rights 2026: Do You Need Planning Permission?

Do you need planning permission for a house extension in London in 2026? Complete guide to permitted development rights for rear, side and double storey extensions. Full 2026 rules and size limits explained.

LCCL Construction

Jul 84 min read

New Build Planning Permission London & Hertfordshire 2026: Complete Guide

Planning permission for a new build house in London or Hertfordshire — complete guide to the planning process, timescales, costs, what affects approval and how LCCL Construction manages it all for you in 2026.

LCCL Construction

Jun 43 min read

House Extension Planning Permission London 2026: Complete Guide

Do you need planning permission for a house extension in London? Complete guide to permitted development rules, the Larger Home Extension Scheme, conservation areas and when planning permission is required in 2026.

LCCL Construction

May 184 min read

Loft Conversion Planning Permission London: Complete Guide for 2026

Most loft conversions in London can be carried out under permitted development rights without needing planning permission. This complete guide covers loft conversion planning permission rules in London, when you do and don't need permission and what to expect from the process.

LCCL Construction

Apr 154 min read

Do I Need Planning Permission for a Rear Extension in London?

Many rear extensions in London can be built without planning permission under permitted development rights. This complete guide explains when you do and don't need planning permission for a rear extension in London, the rules that apply and what to do if your project falls outside permitted development.

LCCL Construction

Apr 155 min read

Permitted Development Rights for House Extensions in London: What You Can Build Without Planning Permission

Permitted development rights allow homeowners in London to build certain house extensions without applying for planning permission, saving time and money. However, the rules are specific and depend on the type of property, size of extension, and whether you are in a conservation area. At LCCL Construction, we advise on permitted development rights for every project and handle all planning applications when they are required.

LCCL Construction

Mar 132 min read

What Is a Party Wall Agreement and Do I Need One?

A party wall agreement is a legal requirement under the Party Wall etc. Act 1996 when your building work involves a shared wall with a neighbour, building on or near the boundary line, or excavating within 3 to 6 metres of a neighbouring property. Most loft conversions on terraced and semi-detached houses in London require party wall agreements. At LCCL Construction, we arrange party wall agreements as part of our design and build service.

LCCL Construction

Mar 132 min read

What clients say

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5.0

average rating is 5 out of 5

“We did a 3x10m single storey rear extension with LCCL recently. It was scheduled to take 12 weeks to complete but with Alex's experience and agile project management, we are ahead of schedule (finished in 10). Alex, and LCCL,is extremely knowledgeable and…”

Christophe · Trustpilot

5.0

average rating is 5 out of 5

“We used Lccl construction first time for our kitchen extension 2019 with a view to build a loft conversion afterwards. We just have had our loft conversion completed including bedroom, bathroom, storage loft it has Juliet balcony with velux windows to the…”

Tracie · Trustpilot

5.0

average rating is 5 out of 5

“We engaged with LCCL Construction to get our loft conversion and house extension project going. The whole process was explained to us in a straight forward way including how the design stages work, timescales, what to expect during the build and the costs…”

Daniel Freedman · Trustpilot

Aleksandar Madari (Anderson), founder of LCCL Construction

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