12 Kitchen Extension Ideas Open Plan

A kitchen extension is not just adding square footage. It is reconfiguring the heart of the home. Unlike a new build, where you start from scratch, an extension must connect to the existing house—matching floor levels, roof lines, and structural connections. The challenge is blending the old with the new while creating a bright, open space that works for cooking, dining, and living. The best open plan kitchen extensions remove the wall between the old kitchen and the new extension, creating one large space.

These 12 open plan kitchen extension ideas span rear, side-return, L-shaped, wraparound, two-story, bifold door, vaulted ceiling, glass box, lantern roof, orangery, lean-to, and passthrough configurations.

1. The Rear Extension (Straight Out the Back)

A rear extension extends straight out from the back of the house. The existing rear wall is removed (or partially removed), and the new extension becomes part of the kitchen-dining-living area. The roof is typically flat or a simple pitched roof (matching the house). The rear extension is the most common type because it works on any site (no side setbacks required). The challenge is the depth (if too deep, the center may be dark). A skylight or roof lantern brings light to the center.

This extension is for most houses, terraced houses, or any site with a rear garden. The emotional effect is linear, bright, and open.

Quick Specs

• Extension depth: 3-6 m (10-20 ft).
• Extension width: full width of the house (4-8 m).
• Roof: flat (with skylights) or pitched (with roof lantern).
• Walls: brick to match existing, or glass (bifold doors).
• Floor: same level as existing (or stepped down).

2. The Side-Return Extension (Filling the Alley)

A side-return extension fills the narrow alley (side return) between a terraced or semi-detached house and its boundary. The side return is typically 1-2 m wide. By extending into this space, you widen the kitchen, creating a rectangular space (full width of the house). The side-return extension is common in Victorian terraced houses (which have a side passage). The challenge is the narrow width (1-2 m) – you must work within the existing walls. The roof is often a glass roof (to bring light into the center of the house).

This extension is for terraced houses, semi-detached houses, or any house with a side passage. The emotional effect is widened, light-filled, and space-maximizing.

Quick Specs

• Side return width: 1-2 m (3-6 ft).
• Extension length: 4-8 m (13-26 ft) (depth of the house).
• Roof: glass (flat or pitched) to bring light in.
• New kitchen width: original kitchen width + side return width = 4-6 m total.

3. The L-Shaped Extension (Rear + Side Return)

An L-shaped extension combines a rear extension and a side-return extension, creating an L-shaped space. The L-shape maximizes the extension area (up to 30 m²) and creates a natural separation between the kitchen (in one leg) and the dining/living area (in the other leg). The L-shape is ideal for corner sites or for houses where the garden is at the side and rear. The challenge is the complex roof (the L-shape has a valley) and the two directions of light.

This extension is for houses with both a rear garden and a side passage. The emotional effect is L-shaped, spacious, and zoned.

Quick Specs

• Rear extension depth: 3-4 m (10-13 ft).
• Side-return width: 1-2 m (3-6 ft).
• Side-return length: full depth of the house (6-10 m).
• Total extension area: 25-40 m² (270-430 sq ft).
• Roof: flat with skylights, or pitched (glass).

4. The Wraparound Extension (Rear + Side + Front)

A wraparound extension extends to the rear, side, and front of the house, creating a large, continuous space that wraps around the corner of the house. The wraparound is for corner sites (where there is no neighbor on one side) and for large extensions (30-50 m²). The challenge is the complex roof (multiple valleys) and the structural support (you may be removing a load-bearing wall). This extension is for corner sites, detached houses, or any house with space on two sides.

This extension is for corner sites, detached houses, or any house with space on two sides. The emotional effect is wraparound, spacious, and corner-oriented.

Quick Specs

• Rear extension depth: 3-5 m.
• Side extension width: 2-4 m.
• Front extension depth: 2-3 m (if applicable).
• Total extension area: 40-60 m² (430-650 sq ft).
• Roof: flat with skylights, or multiple glass lanterns.

5. The Two-Story Extension (Kitchen Below, Bedroom Above)

A two-story extension adds a kitchen on the ground floor and a bedroom (or bathroom) on the first floor. The two-story extension is more expensive (requires a full foundation and roof) but adds valuable floor area on both levels. The ground floor kitchen extension is designed like a single-story extension (open plan, bifold doors). The first floor extension must match the existing house (same roof line, same window style). The challenge is the cost (foundation, structure, roof) and the planning permission (two-story extensions are more scrutinized).

This extension is for houses where additional bedrooms are needed, or for maximizing floor area. The emotional effect is two-story, space-maximizing, and vertical.

Quick Specs

• Ground floor extension: same as rear extension (3-6 m deep).
• First floor extension: same footprint as ground floor (or smaller).
• Total extension area: 30-60 m² (including both floors).
• First floor use: bedroom, bathroom, or home office.
• Roof: pitched to match the house (or flat with parapet).

6. The Bifold Door Extension (Glass Wall to Garden)

A bifold door extension is not about size—it is about the connection to the garden. The extension has a full-width wall of bifold doors (or sliding doors) that open completely, removing the barrier between inside and outside. The extension can be shallow (2-3 m deep) or deep (4-5 m). The bifold doors are typically aluminum or timber, with floor-to-ceiling glass. The challenge is the cost (bifold doors are expensive) and the thermal performance (glass loses heat). Use double or triple glazing and a low threshold (flush with the outside patio).

This extension is for houses with a garden, or for any extension where indoor-outdoor flow is the priority. The emotional effect is glass-walled, garden-connected, and open.

Quick Specs

• Extension depth: 2-5 m (6-16 ft).
• Bifold door width: full width of the extension (4-8 m).
• Bifold door height: floor-to-ceiling (2.1-2.4 m).
• Threshold: flush with outside patio (no step).
• Roof: flat with skylights, or pitched with roof lantern.

7. The Vaulted Ceiling Extension (Dramatic Height, Skylights)

A vaulted ceiling extension has a high, sloping ceiling (4-6 m tall) that follows the roof pitch. The vaulted ceiling creates a dramatic, spacious feel and allows for large windows or skylights. The extension is often built with a pitched roof (glass or solid) and exposed rafters. The vaulted ceiling is expensive (requires a structural ridge beam and more materials) and harder to heat (heat rises). The challenge is the cost and the thermal performance (insulate the roof well).

This extension is for houses where drama and height are desired, or for kitchens with high ceilings. The emotional effect is vaulted, dramatic, and light-filled.

Quick Specs

• Ceiling height: 4-6 m (13-20 ft) at the ridge.
• Roof pitch: 30-45 degrees.
• Skylights: full-length (glass roof) or individual skylights.
• Ridge beam: steel or laminated timber (structural).
• Insulation: between rafters (high-performance).

8. The Glass Box Extension (Frameless Glass, Minimalist)

A glass box extension is a minimalist extension with frameless glass walls and a glass roof. The extension looks like a glass box attached to the house. The structure is steel or aluminum (minimal frames). The glass box is fully transparent (walls and roof), bringing maximum light into the kitchen. The challenge is the cost (structural glass is expensive), the thermal performance (glass loses heat), and the privacy (neighbors can see in). Use double or triple glazing and frosted glass or blinds for privacy.

This extension is for modern houses, or for clients who want a minimalist, transparent extension. The emotional effect is glass box, transparent, and modern.

Quick Specs

• Extension size: 3 m x 4 m to 5 m x 6 m.
• Glass: double or triple glazing (low-E).
• Frame: steel or aluminum (minimal).
• Roof: glass (frameless or with minimal frames).
• Floor: same level as existing (flush with outside).

9. The Lantern Roof Extension (Central Skylight)

A lantern roof extension has a flat roof with a central roof lantern (a raised glass box) that brings light into the center of the space. The roof lantern is typically 1-2 m wide and 2-4 m long, with glass on all four sides. The lantern roof is common in extensions where the roof is flat (or low-pitched). The challenge is the cost (the lantern is custom-made) and the detailing (the lantern must be watertight). This extension is for houses with a flat roof, or for any extension where natural light is needed in the center.

This extension is for houses with a flat roof, or for any extension where natural light is needed in the center. The emotional effect is lantern-roofed, light-centered, and bright.

Quick Specs

• Flat roof area: 3 m x 4 m to 6 m x 8 m.
• Roof lantern size: 1 m x 2 m to 2 m x 4 m.
• Lantern height: 0.3-0.6 m above the roof.
• Lantern glass: double or triple glazing.
• Ceiling height: 2.4-2.7 m (standard).

10. The Orangery Extension (Brick Pillars, Glass Roof, Solid Walls)

An orangery is a hybrid between a solid extension and a conservatory. It has brick (or stone) pillars at the corners, a glass roof (often with a central lantern), and glass windows between the pillars. The orangery has more solid wall than a conservatory (better insulation) and more glass than a solid extension (more light). The orangery is popular for traditional houses (Georgian, Victorian) because it matches the architectural style. The challenge is the cost (brick pillars, glass roof, lantern) and the thermal performance (the glass roof loses heat). Use double glazing and insulated panels in the roof.

This extension is for traditional houses (Georgian, Victorian), or for clients who want a classic orangery look. The emotional effect is orangery, classic, and light-filled.

Quick Specs

• Extension size: 3 m x 4 m to 5 m x 6 m.
• Brick pillars: at the four corners (0.3-0.5 m wide).
• Glass roof: with central lantern (or full glass).
• Glass windows: between pillars (floor-to-ceiling).
• Wall: brick up to sill height (0.9-1.2 m).

11. The Lean-To Extension (Simple Pitched Roof, Budget)

A lean-to extension has a single-pitch roof that slopes down from the existing house. The roof is simple to build (rafters bear on the house wall and a new beam). The lean-to is the most budget-friendly extension (simple structure, no complex roof valleys). The challenge is the lower ceiling height at the far end (the roof slopes down). The ceiling height must be at least 2.2 m at the far end for a kitchen. This extension is for budget-conscious homeowners, or for any extension where cost is the primary concern.

This extension is for budget-conscious homeowners, or for any extension where cost is the primary concern. The emotional effect is lean-to, simple, and budget-friendly.

Quick Specs

• Extension depth: 3-5 m (10-16 ft).
• Roof slope: 5-15 degrees (minimum).
• Ceiling height at house: 2.4-2.7 m (standard).
• Ceiling height at far end: 2.2 m minimum.
• Roof: polycarbonate (budget) or glass (more expensive).

12. The Passthrough Extension (Window to Counter, Serving Hatch)

A passthrough extension is not a full extension—it is a small extension (1-2 m deep) with a large window or serving hatch that connects the kitchen to the garden. The passthrough is for houses where a full extension is not possible (budget, planning permission, or structural constraints). The passthrough creates a indoor-outdoor connection without adding much floor area. The countertop extends through the window to the outside (a “passthrough counter”). The challenge is the small space (1-2 m deep) – you can’t fit a full kitchen, but you can add a serving hatch or a breakfast bar.

This extension is for budget-conscious homeowners, or for houses where a full extension is not possible. The emotional effect is passthrough, serving-hatch, and indoor-outdoor.

Quick Specs

• Extension depth: 1-2 m (3-6 ft).
• Passthrough window: full width (2-4 m wide), counter height.
• Counter: continuous from inside to outside.
• Roof: flat or lean-to (polycarbonate or glass).
• Use: breakfast bar, serving hatch, or small dining area.

Comparison Summary

Conclusion

A kitchen extension is a transformative project. Unlike a new kitchen in the same footprint, an extension changes the shape and feel of the house. The challenge is not just adding space—it is creating a bright, open, functional kitchen-dining-living area that connects to the garden.

The twelve extension ideas presented here offer different strategies for different houses, budgets, and sites.

The Rear Extension says: go straight out the back. This works on any site. The risk is the dark center (use a roof lantern).

The Side-Return Extension says: fill the alley. This is for terraced houses with a side passage. The risk is the narrow width.

The L-Shaped Extension says: go both rear and side. This creates a large L-shaped space. The risk is the complex roof.

The Wraparound Extension says: wrap around the corner. This is for corner sites. The risk is the multiple roof valleys.

The Two-Story Extension says: add a kitchen downstairs and a bedroom upstairs. This is for maximizing floor area. The risk is the higher cost.

The Bifold Door Extension says: focus on the garden connection. The glass wall opens completely. The risk is the cost of bifold doors.

The Vaulted Ceiling Extension says: create drama with height. The high ceiling feels spacious. The risk is the heating cost.

The Glass Box Extension says: be minimalist and transparent. The glass walls disappear. The risk is the cost of structural glass.

The Lantern Roof Extension says: bring light to the center. The roof lantern is a classic. The risk is the detailing (watertight).

The Orangery Extension says: blend solid walls with a glass roof. This is for traditional houses. The risk is the cost (brick pillars, custom glass).

The Lean-To Extension says: keep it simple and budget-friendly. One sloping roof. The risk is the low ceiling at the far end.

The Passthrough Extension says: just a serving hatch. This is for very small budgets or where a full extension is not possible.

When designing a kitchen extension, ask: What is the budget? A lean-to is the cheapest. A glass box is the most expensive. Choose the extension type that fits the budget.

Ask: What is the site? A terraced house with a side passage is perfect for a side-return extension. A corner site is perfect for an L-shaped or wraparound extension. A house with a garden is perfect for a rear extension with bifold doors.

Ask: What is the existing house? A Victorian terraced house looks best with an orangery or a side-return with a glass roof. A modern house looks best with a glass box or a flat roof with a lantern.

Ask: What is the planning permission? Rear extensions up to 4 m deep (detached) or 3 m deep (semi/terraced) often do not need planning permission (permitted development). Side extensions almost always need planning permission. Check local rules.

Ask: What is the structural work? Removing an external wall requires a structural beam (steel or glulam). The beam may be visible (exposed) or hidden in the ceiling. The cost of the beam can be significant.

Ask: What is the heating? A large glass extension loses heat. Underfloor heating is recommended (to keep the space warm without radiators on the walls). High-performance glazing (double or triple glazing) is essential.

The best kitchen extension is not the largest or the most expensive. It is the one where the morning sun hits the breakfast table, where the bifold doors open to the garden, where the roof lantern brings light to the center, where the kitchen is functional, and where the family wants to spend time. It is a plan for living, not just for cooking.