House Extensions builders in Mill Hill NW7 North West London

In 2008 we built a two story extension in Mill Hill, NW7 Postcode – North West London. It was more like an L shape house extension, we had to build a kitchen extension at the back too. Extensive refurbishment to the semi detached London house, completely transform it into a luxury property.

The garage before demolition
before demolition
The side garage demolished
side garage demolished

We started with a boring semidetached London home in North London, Mill Hill ( good area ) and by the time we were finished, all that was missing was a swimming pool.

The soil in that particular area in Mill Hill, North London, is below the water table and the quality of the clay very poor. It meant that we had to dig a foundation of over 2.7 meters deep.

Marking the foundation
foundation marking for new side extension

Just for the bathrooms, we had to run four mains waste pipes. A normal house has just one. Two smaller inspection chambers and one main manhole. The garden had to have drainage too, in order to keep the artificial turf dry.From the new kitchen, you could run a restaurant, I have seen restaurants with smaller kitchen space and kitchen appliances.
drains runs through foundations

Deep foundation

deep footings

The concrete for the foundation C25 ready mix type

concrete lorry foundation
Dry concrete foundation below ground level
dried concrete foundation for extension
Building the walls under the DPC level was done when the concrete and waste pipes were laid in place.
building walls below DPC

The walls were cavity walls, blocks skin, internal and external. For insulation, the bricklayers used Kingspan 50 mm thick. Because the house owners wanted the ground floor to be open plan, giving them more space and also making the property look more elegant compared to London houses, there was major metal works involved to make the openings.
RSJ Metal beams
RSJ metal beams

The builders started building the foundation, late February and two months later, the shell building was done, ready for the joist works for the floors and roofing.
joist works floor
The new roof for the side extension, was built to make it look like it is a single roof, part of the original building.
new roof over side extension
For the roof, the roofers to remove existing old roof tiles to be reused later on and strip the roof back to the rafters. New breathable membrane was used as underlay, more effective than traditional bitumen underlay because it gives better ventilation and also safer from a fire point of view. The breathable underlay also lasts longer when exposed to the weather, like very hot temperatures in the summer and cold in the winter. The roofers also changed all the roof battens with treated timber battens.

side extension ready

Once the roof was finished, the internal work could start. The external walls were rendered using sand and cement mix, and that includes the old walls of the property after the old render was removed back to the brickwork.

Full rewiring, the electricians used over 3.7 km of electrical cable, the plumber about 0.7 km of pipes, 520 litres of paint and other scary figures. The underfloor heating for 2 floors, downstairs and upstairs, required a new megaflow boiler. Everything is protected by CCTV, recorded live on the internet, no tapes involved for security.
electrical wirings
Underfloor heating pipes inside a concrete floor
underfloor heating pipes

The final pictures of the 2 story house extension, side and rear extension :

Living room, open space, marble tiling floor
living room open space

The kitchen with island sink and a standard sink
kitchen fitting

The builders built three new bathrooms, five bedrooms.

You can see the process of building the house extension in Mill Hill by watching the video clip below. The house extension builders finished the job in 7 months and that includes the interior and exterior refurbishment.

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