House Extension: The Process

Make of best of your London home
with a House Extension

The Process: How We Carry Out a House Extension

Typically, once we’ve agreed everything and obtained all the necessary planning permission, the process order of a typical house extension is as follows:

Demolition of existing structure, as required

Remove existing structure as required, keeping disturbance to a minimum

Remove existing structure as required

The first stage of the process would be to remove any existing section of the house, in this case the old kitchen.

Demolition and correct disposal of rubble.

Prepare exiting brickwork for future joining of new brickwork.

Clearing the Ground

Staking out the gorund

Staking out the ground

Clearing all the ground

Ground clearance

Once the old kitchen is cleared we then do the ground clearance work.

Any plants that need to be re-planted should be pointed out prior to this stage.

It’s probably better if you clear the plants you want to keep before we start. The Ground is then ready to be marked out, in accordance to the plans.

Laying the Foundation

Building foundation layers

Foundation laid

Foundation Trench

Foundation Trench

The trenches for the foundation can then be dug ready for the laying of all the foundations with strict accordance the plans and architecture of the extension.

The new building foundation will be either strip, wide strip or raft and pile.

A 600mm wide, 1 metre deep trench will suffice For the majority of extensions, dependent on the kind of soil.

The whole point of foundations is to give a good firm footing on which the extension is to be constructed. Additional to protect against soil heave – any future movement of the ground around the extension.

Laying drainage pipes

Laying of the drainage system

Drainage pipe laid at this stage

Next, all the drainage system is laid in place, inspection of this required before the backfilling can proceed.

Steal work

Steal R S J  Framework

Steal Frame

Steal Base sitting in foundation trench

Steal Base sitting in trench

Now the construction starts to take shape as the steel work is put in place. Usually consisting of fabricated steel sleepers, uprights and R.S.J’s. All, of which have been designed by the structural engineer.

This may involve primary and secondary framing.

The key to success for any steel building project starts with a properly prepared and executed foundation.

Laying the concrete floor

Concrete floor with steel re-enforceing

Next the floor goes down

The laying of the concrete floor starts with a layer of hardcore then sub base and the all important damp proofing. It is at the stage that the openings are formed.

Large areas

If we are laying a large area of concrete, more that 4m wide or long then we will lay it in sections to prevent it from cracking during expansion and contraction. To do this, we divide the formwork(wooden surrounds) into bays with control joints between the sections.

After each section has been laid we can remove the supports and lay the next section of concrete.

Brickwork stage

brick laying starts

brick work can now start

Building internal and external walls and adding roof.

Once the floor has hardened the brickwork for the walls can begin which in turn enables the roof to be fitted.

This is when the whole structure starts to really take shape.

It is at this stage any access scaffolding can be erected

Doors and Windows

Hanging of the doors

Door hanging

Window fitting

Fitting of windows

Now the fitting and hanging doors and windows can start

The new windows will come with a new exterior window frame. These are inserted into the frame into the opening using wedges to fit under the sill to push it up against the brickwork.

The sill will be perfectly square and using a spirit level the sill will be checked to make it is completely horizontal before fixing.

Next using the spirit level again to check the angle of the jambs, which will be vertically upright. Using wedges to push them into position if necessary. Checking with the spirit level and adjust the wedges as necessary. Once we are satisfied that the frame is perfectly square, it can be secured to the brickwork. Drill holes through the frame and brickwork at intervals.

Electricians to lay wiring.

The electrician lay the cabling

Electrician lay cabling

Prior to the plasterer we can have the electrician lay all the cabling.

cable ducting

all cabling requires 17th Edition IEE certificate.

by certified an approved electrician

There is the “first fit” for all the cabling and back boxes followed by the “second fit” of all the fittings

included lots of contingencies for various future wiring

Plastering stage

Plastering and rendering makes everything look neater

Plasterers start their work

Interior walls and ceiling plastered as required.

Plaster takes about 2 weeks to dry, however this will not hinder the building process.
Recently colored plaster has come unto the market which removes the need for the wall to be painted!


tiles go down

Ceramic floor tiles

Then the flooring goes in, be it wooded or tiled dependent on the primary use of the house extension.
Carpeting (if required) should not be fitted at this stage. That should be done after the completion of all building work.

Fixtures and fittings

Tiles and bathroom items

Floor tiles fixtures and fitting

Kitchen or bathroom fitting as required.

Most extensions will include the fitting of an extra W/C as this will have a positive effect on the value of the property as well as fulfilling a practical need.

Your New

extended kitchen
playroom for the children
utility room

is now ready for you to use and enjoy!

Existing sections of the property are removed, as required

Rubble is safely and correctly disposed of and is cleared up as we go

The new brickwork is prepared in anticipation of future amalgamation with the new brickwork

Clearing the Ground
Ground clearance starts as soon as the room is cleared

The ground is marked out, in accordance with the plans

(Make sure that you move your plants!)

Laying the Foundations
A solid foundation on which to build an extension is essential to guard against soil heave

A trench 60m wide, 1m is created (suitable for most extensions)

A foundation will be either strip, wide strip or raft and pile

The foundations are dug in strict accordance with the architect’s plans

Drainage Pipes

The drainage system is laid

Inspection will be required before backfiling can proceed.

Steel Work

Designed by the structural engineer, RSJs, uprights or fabricated steel sleepers are put in place

Primary or secondary framing may be required

Your new extension is starting to take shape

Laying the Concrete Floor

A layer of hardcore, then sub-base is laid; then the damp proofing

The openings are formed

Specialist techniques are used for large areas

The Brickwork

Once the floor has hardened, your property extension starts to come to life

The internal and external walls are built; the roof is added

Any excess scaffolding can be erected

Doors and Windows

Your new windows are inserted into their new exterior window frames, using tried and trusted techniques to make sure they are perfectly aligned and horizontal.

Your new doors are hung , using the same precision techniques

The Electrics

All cabling requires a 17th edition IEE certificate (we can take care of this for you)

“First fit” cabling is installed, followed by the “second fit”

Contingencies are built into the installation for various future wiring potential scenarios


Interior walls and ceilings are plastered, as required.


The type being agreed with you in advance, the flooring is laid

Fixtures and Fittings

Kitchen or bathroom fittings are installed, as required

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