Building a kitchen extension

Do you know how a kitchen extension is built ? We’ll try to write a How to build a kitchen extension guide that can help you understand better the construction process. Kitchen extension company in London. If the kitchen extension is at the rear of the property, and it will be extended into the garden, the normal size for the kitchen extension is about 5 meters by 3 meters and the new dwelling is built where normally the garden patio is.

Foundation or Footings
There are two ways that the kitchen extension builders can dig the foundation. If the property is a terraced house and there is no access to the garden through an alleyway, the trench for the foundation will have to be manually dug, the way it is illustrated in the picture bellow.

Fondation for a rear kitchen extension

If there is access to the garden, mechanical digger can be used, making the job faster and cheaper.
Mechanical digger digging foundation

The soil from the foundation will be taken by wheelbarrows, through the main house and to a skip that usually is located onto the drive way or onto the street if necessary. A street skip licence will be needed if the skip is kept on the main road and it will have to be illuminated during the night for safety reasons. You should expect some damages to the walls and floor, as there will be heavy traffic caused by workers and materials.
Skip on the driveway

The foundation should be about 1.2 meters deep and 600 mm or 0.6 meters wide, depending on the quality of the soil. Solid clay soil is the best type for foundation, sandy type will require deeper footings. The Building Control Inspector from the local council will advise how deep it should be, before the concrete is poured in.
Trench footings
Again, if the house is a terraced property and there is no access for the concrete lorry to pour the concrete directly into the foundation, a concrete pump can be used.
Concrete pump and lorry
The concrete is pushed through a 4-5 inch pipe.
concrete pipe
If the concrete lorry has direct access to the foundation, it will make the jobs easier, faster, and cheaper.
Concrete poured directly in the foundation

After the concrete is pored in the foundation, it will takes few days for the concrete to set before the walls for the foundation can be built. New plumbing waste or soil pipes will be needed in most cases, but we will write about how to run new pipes or construct a new manhole in a future blog post.
Footings with concrete

Building the walls for a kitchen extension
If the new kitchen extension is built using cavity walls ( most of them will be constructed with cavity walls for better heath conservation ) the walls under the DPC (damp proof course) can be built using concrete blocks, topped with engineered bricks to stop the damp rising to the main walls.

The walls for the kitchen extension can be double skin block-work or the external skin brick-work and the internal skin block work. Using blocks for the walls,inside and outside, will help the bricklayer finish the job faster,but there are some drawbacks as the external and sometimes inside walls too, will have to be rendered with a smooth finish or pebble dashing, to match the exterior of the property. Building Blocks are also cheaper than bricks.

Blockwork double skin cavity wall
Cavity walls with external brick faced skin, has the advantage of being easier to maintain long term and it looks better, especially in London, where traditionally the bricks are the favourite choice of building houses.

Brick faced cavity walls

The gap in between the walls can be be from 35 mm to 900 mm, however, the most popular choice is 75mm. The bricklayer will have to keep the walls clean and free of mortar, as the mortar for the masonry, can act as a bridge between the walls, and damp can travel from the external wall, to the internal wall. Insulation is then inserted as building process takes place.

Building the opening for doors and windows is done by using wooden frames and build the walls around it. Experienced bricklayers can do without frames, however it is recommended to use them to make sure all the openings are perfectly square, thus avoiding any nasty surprises when fitting and installing the doors and windows.
Kitchen extension interior
Concrete lintels can be used for walls that will be rendered or cavity wall metal lintels.
Metal cavity lintels

Building the Roof for the kitchen extension
There are two main choices for the roofing. Flat roof and Pitched roof. We will start with the flat roof, as it is cheaper to build and a popular choice. The carpenter will have to lay wall plates on top of the internal wall and attach the wallplates to the walls using brackets. The wallplates are timbers , 47mm x 100mm or 4” by 2” as is known among the carpenters.
basic flat roof construction
Flat roofs can be so called Cold Flat Roof or Warm Flat Roof, depends where the insulation is located and the gap between the ceiling and top surface of the roof itself.
structure of the flat roof
The timber used for the main structure of the flat roof should be water treated to last longer.
timber roofing
Finally, the external grade plywood can be laid after the slope of the roof is set by using runners ( the flat roof just looks flat but actually has a slope to allow the rain water to run off into the guttering ) and then the bitumen layers can be cross laid.
bitumen layers for flat roof

A pitched kitchen extension roof looks better and it will last longer.
pitched kitchen extension roof

Using old roof tiles helps matching the new extension roof to the old property.
kitchen extension

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