Design + build / Added space

House Extensions Dublin

A house extension should solve more than floor area. Top Builders designs and builds Dublin extensions around planning, structure, daylight, the garden, the existing rooms and the construction route through an occupied neighbourhood.

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Contemporary brick and glass house extension opening to a Dublin garden

Feasibility first

Before drawing the new room, test the property and the route to build it.

Can the brief fit the site?

Measure garden depth, orientation, neighbours, boundaries, drains, trees and the rooms that must remain useful.

What is the planning route?

Check prior development and the exact proposal against current requirements before relying on exemption.

How will it be built?

Plan access for demolition, concrete, steel, glazing and finishes, particularly on terraced sites.

What happens to the old ground floor?

Coordinate internal openings, floor levels, kitchen, utilities, heating and electrical work with the addition.

Interior connection between a house extension and existing rooms

The extension earns its value at the threshold back into the original house—not only at the garden façade.

Choose the intervention

Different extension types solve different constraints.

Rear

Direct garden connection and a new kitchen/living edge.

Side return

Use narrow residual space while managing boundaries and daylight.

Wraparound

Combine rear and side work where the site and planning route support it.

Two storey

Add rooms at both levels with greater planning, roof and occupation complexity.

EXTENSION / JUNCTION 06

New structure, old structure, water, insulation and finishes all meet at one line. Detail that line early.

Quote variables

What shapes a Dublin house extension quote.

01Footprint, height and planning complexity
02Ground conditions, drainage and structural frame
03Site access and protection of the existing home
04Roof form, glazing and external envelope
05Kitchen, services and depth of internal renovation
06Finish, joinery and external works specification

Detailed service guide

House Extensions: detailed scope and decisions.

Substantively updated 22 August 2026

A house extension should improve how the entire home works, not just add square metres. The best route starts with the property, the planning position, structure, daylight, garden connection and the rooms that will lead into the new space.

Top Builders delivers house extensions in Dublin through a coordinated design-and-build process, bringing the new construction and the necessary renovation of the existing house into one clearly defined project.

Choose the right form

Which type of house extension suits your home?

The right extension type depends on the site, house form, required rooms, planning constraints and the effect on the existing layout.

Rear, kitchen and side extensions

A rear house extension is often used to create a larger kitchen, dining and living space with a stronger garden connection. A side or side-return extension can use a narrow strip of land to widen the plan, improve circulation or add utility and storage space.

Single-storey, wraparound and smaller extensions

A single-storey or ground-floor extension can transform daily living without adding an upper level. A wraparound scheme combines side and rear space, while a smaller extension can be the better answer where one precise change unlocks the existing rooms.

Two-storey and house-specific extensions

A two-storey extension can add accommodation on both levels but brings additional planning, structural, roof and service questions. Bungalows, terraces, semi-detached houses and period homes each have different boundaries, access routes, roof forms and old-to-new junctions; a modern design still needs to respond to those conditions.

Feasibility before form

House-extension design and build starts with the existing property

Before a layout is treated as buildable, the team needs to understand the available footprint, previous additions, site access, boundaries, drainage, ground conditions, existing services and the structure that will connect old and new.

Architectural design, structural engineering and construction information serve different purposes. Responsibilities for drawings, calculations, applications and site decisions should be established early, whether the professionals are appointed through the project or directly by the homeowner.

The rooms and problems the extension must resolve
Access for excavation, concrete, steel, glazing and waste removal
Structural openings and support to the existing house
Roof form, daylight, privacy and garden connection
Drainage, plumbing, heating, ventilation and electrical routes
The renovation needed where the extension meets the existing rooms

Permission and compliance

Do you need planning permission for a house extension in Dublin?

Some residential extensions may qualify as exempted development, while others require planning permission. The answer is property- and proposal-specific.

Extension size, height, position, remaining private open space, previous development, property status and local constraints can all affect the planning route. Exempted development is conditional, so a proposal should not be assumed exempt from one measurement alone.

The project may also require structural design, building-regulation coordination and other professional inputs regardless of whether a planning application is needed. Current requirements should be confirmed for the particular address before construction is committed.

A scope before a price

How much does a house extension cost in Dublin?

There is no reliable universal cost per square metre for every extension because equal floor areas can require very different work.

A useful house-extension quotation is based on the design, existing conditions and an agreed level of completion. A rear kitchen extension with a wide structural opening, extensive glazing and major service changes cannot be compared directly with a simpler enclosed addition of the same size.

Extension size, storeys, shape and structural design
Ground conditions, drainage and site access
Demolition, temporary works and alterations to the existing house
Roof form, windows, external doors, rooflights and other glazing
Kitchen, bathroom, heating, ventilation and electrical requirements
Insulation, airtightness, joinery, flooring and finish specification
Design, engineering, permission and other project-specific professional inputs

From idea to handover

A coordinated house-extension process

1. Define the brief and assess the site

Start with the additional space, layout problems, budget priorities and timing. Review the house and site to identify the information and professional assessments the project needs.

2. Develop the design and permission route

Test the extension against the existing plan, structure, daylight, garden, access and current planning requirements. Develop the architectural and engineering information needed for the selected route.

3. Fix the scope and quotation

Define what is included in the new build, what changes inside the existing home, the intended finish level and the responsibilities for kitchens, glazing, specialist systems and professional inputs.

4. Build, connect and finish

Sequence site setup, groundworks, structure, envelope, services and the opening into the house. Complete the internal connection and finishes before inspection and handover.

Questions before scope

House extension questions before the drawings become expensive to change.

01Does Top Builders provide design as well as construction?

Yes. House extensions are offered through an in-house design-and-build route so feasibility, permissions, structure, services, construction and finishing can be coordinated from the outset.

02Do all house extensions in Dublin need planning permission?

No, but exempted-development conditions are property-specific. Previous additions, position, height, boundaries and planning status are checked before the project relies on an exemption.

03Should the existing ground floor be renovated at the same time?

Often. The extension performs better when circulation, kitchen position, storage, services and the rooms left inside the original house are designed as one scope.

04Can we live in the house during construction?

Possibly for parts of the programme. Access, structural work, weathering, dust, fire separation and service interruptions determine where occupation is safe and sensible.

05When can you provide a meaningful quote?

Once the project information defines size, structure, envelope, glazing, services, existing-house work, access and finish responsibilities. Early budgets remain conditional until those variables are resolved.

06How much does a house extension cost in Dublin?

Cost depends on the extension's size and form, site access, ground and drainage conditions, structure, glazing, service changes, work to the existing house and finish specification. A project-specific design and scope are needed before a meaningful quotation can be prepared.

07Do I need planning permission for an extension in Ireland?

Not every extension requires a planning application, but exempted development is subject to conditions and previous work can affect the position. Confirm the current planning route for your property and exact proposal before committing to construction.

08How much can I extend my house?

That depends on the site, house type, previous development, proposed height and position, remaining private open space and any property-specific constraints. A designer or planning professional should assess the current rules against the address and proposal.

09Which house-extension types can Top Builders deliver?

Projects can include rear, kitchen, side, side-return, single-storey, two-storey, wraparound, ground-floor and smaller extensions, subject to the property, planning position and project fit.

10Can you extend a terraced, semi-detached, bungalow or period house?

These house types can all be considered, but each brings different questions around access, boundaries, roof form, neighbours, original fabric and the junction between old and new. Feasibility is assessed for the individual property.

11Will I need an architect or structural engineer for my extension?

The required professional team depends on the project. Extensions commonly need architectural information and project-specific structural design. The scope should identify who is responsible for design, calculations, applications, inspections and construction information.

12Can the existing ground floor be renovated with the extension?

Yes. Many projects work best when the extension and the rooms leading into it are designed as one scheme, including the structural opening, kitchen, utility space, circulation, services, flooring and decoration.