Construction Design 1

[ Home ] [ Site Context ] [ Foundations ] [ Walls Up To DPC ] [ Ground Floor Construction ] [ Walls ] [ Openings ] [ Intermediate Floors ]

Walls

Once the ground floor is completed, the walls can then be built. It is at this stage that visually the house begins to take shape. The houses on the site all used cavity walls, the most common type for this type of building. 

Cross-section of the wall, showing the cavity with a layer of insulation (silver covering on the grey inner leaf). The white plastic element at the top is where an opening for a window will be.

This diagram shows how the cavity wall ties hold the inner and outer leaf together. This prevents the wall from buckling. The cavity itself is usually between 50mm and as it was on the site, 75mm. The cavity ties can vary in size and shape, but the standard types used in Britain are made from either stainless steel or strong rigid plastic, both very durable materials that will not rust. The ties have a drip in the middle, which prevents water passing across them.

To prevent the wall from buckling, the load must be evenly distributed. To do this, the builders alternate the position of the bricks so they overlap and improve rigidity.

It is not entirely necessary to alternate the bricks on every course, as alternation every 4 would be acceptable. Bricks pointing into the house are avoided, however, as they act as thermal conductors. The bricks used on the site are standard sized bricks (225mm x 112.5mm x 75mm), which cannot be built up at more than 1 metre at a time, to prevent the risk of squashing out mortar between bricks at the bottom of the wall. The mortar used to bond the bricks is a mixture of cement, lime and sand in the proportion of 1:1:6 respectively. The mortar should be weaker than bricks, so that the wall is allowed to settle.

This image shows how the developers save money by using the larger, less attractive, trench blocks on the wall that will be on the inside of the garage. Being a structural element, it is used to hold up the roof of the garage.

By law, all installations for gas must be on the exterior of the building. This is for safety reasons and so they are easily accessible for gas engineers. 

This image shows the internal view of the wall before rendering. At the base of the wall, you can see the DPC. Once the house is water-tight, the internal wall will be plastered to it give a smooth finish. 

Insulation

These days, insulating the building is essential. The architects and builders must reach certain U-Values to ensure the building complies with regulations, and does not waste energy. To achieve this the builders use insulation in the floors, windows and doors, walls and the roof. Here, I will look at the insulation in the walls. 

The majority of the houses on the site had a single layer of insulation within the cavity. The insulation decreases the amount of heat lost by the building, reducing energy wastage.

Some of the houses on the site had two layers of insulation within the cavity. This will inevitably reduce heat loss further and thus, save more energy. 

Diagram showing the cross-section of the cavity wall. The insulation is attached to the inner leaf.