Category Archives: Building Materials

Waterbar for construction joints

No, it’s not a place where you go to get wasted on the finest Evian around. It’s used to waterproof construction joints of retained concrete structures so that they become integrally waterproof – defined within BS8102:2009 as Type B waterproofing. A construction joint is where one form of construction stops and another starts, thus forming a weak path for water to enter through. Hydrophilic water bars are regularly used when activated by moisture. It’s characterised by high elasticity and high tensile strength. It is usually made of natural sodium bentonite clay and synthetic rubber. When it comes into contact with water it can expand up to 400%, from what I’ve seen it at least doubles its dry volume forming a positive seal.

Waterbar can be included in; both vertical and horizontal non-moving concrete construction joints, new to existing concrete construction, irregular surfaces and around through wall penetrations such as plumbing and utility pipes. Water bar can be; mounted using adhesive onto a cleaned substrate. Where there is around 80mm of concrete cover from the water bearing side it can be mechanically fixed. The waterbars should come with a test certificate for authenticity. They usually come in 25m lengths and ranging from 190mm to 320mm wide. When visiting site, I have seen waterbar used when a basement wall is being erected and the perimeter wall is being built up.

Lintels

A lintel is essentially a structural support that spans an opening in a wall. The use of lintels in architecture dates back many centuries, from the highly decorative masonry creations used in ancient Greece, to the timber lintels seen in Tudor times. These days lintels are mainly constructed in concrete or steel.

Steel lintels are lighter than concrete and are easier to manually handle than concrete. Steel lintels are popular because they don’t interrupt the look of brick work by being hidden during their construction process. Most steel lintels are made from pre-galvanised steel which is cut into shape.

When selecting a steel lintel you have to consider; the type of wall under construction (cavity, solid, timber etc) and the lintel length which is worked out by calculating the total width of the structural opening plus 150mm end bearings at each end. Another important calculation to consider is the dead and imposed loads the lintel will be under.

Lintels offer structural support and play a part in reducing heat loss in a building. An opening in the building fabric is a possible route for heat to escape which is known as thermal bridging. Thermal brake plates are lintels which have been designed to overcome thermal bridging. There are various designs of lintels which help eliminate thermal bridging.

Cavity closers

 

Cavity closers are insulated extrusions for closing wall cavities at openings such as window reveals and door reveals. If a cavity is not correctly closed around a reveal, water ingress can occur, this can lead to the seeping of damp and mould around the frame.

The use of a cavity closer will prevent the ingress of water around a window or door, as required for compliance with Building regulations part C. (Site preparation and resistance to contaminates and moisture).To achieve this it is important to set back the frame of a window a minimum of 30mm in to the cavity and to seal with a waterproof sealant around the frame. Cavity closers with ridges help prevent water ingress.

Cavity closers also help prevent heat loss and cold penetration. Cold bridging is when an area of a building has significantly higher heat transfer than the surrounding materials which results in an overall reduction in the thermal insulation of the building. Cold bridging problems are outlined in Building Regs part L. (Conservation of fuel and power). Insulated cavity closers are used to protect against thermal loss. Thermal loss can also result in problems of condensation, staining and mould growth on reveals. Prolonged exposure to thermal loss can result in internal plaster deterioration and damaged paint.

Cavity closers help to create a fire barrier, and thus to comply with part B Building regulations (Fire Safety), a fire rated cavity closer can be used. A fire rated cavity closer can prevent the spread of fire for up to 60mins. A purely insulated cavity closer will not comply with building regs part B.

The more you can reduce heat loss within a building the more sustainable your home will be. The minimum thermal resistance path through the cavity closer must be at least 0.45m2k/w. The higher the number, the lower the heat loss. First fit Cavity closers are for buildings being refurbished. If the windows alone are being replaced, a second fix cavity closer will be suitable. The cavity closer you choose should be the same size of the cavity.

To comply with Building regulations C,B and L you will need to select a cavity closer which is insulated, fire rated and has a thermal resistance path of 0.45m2 k/w (R Value).

Bricks, spoiled for choice

 

Facing bricks

Facing bricks are the most popular type of brick and have been the facade material of choice in the UK for thousands of years. They are primarily used for external walls of a building and are chosen for their aesthetic qualities. Facing bricks include any brick which is sufficiently hard burned to carry normal loads and is capable of withstanding the effects of rain, wind, soot and frost without breaking up.

Engineering bricks

Engineering bricks have high compressive strength and low water absorption. They are used for their physical characteristics and not their appearance. They are traditionally used in civil engineering projects and are most suitable for applications where strength and resistance to frost attack and water are important. Situations where they are used include, ground-works, manholes, sewers, retaining walls and damp proof courses. The two best known engineering bricks are the red Southwater brick and the blue Staffordshire brick. Both are very hard and dense and do not readily absorb water. The ultimate crushing resistance of engineering bricks is greater than 50N/mm2.

Engineering bricks are rated as class A or B with class A being the strongest. Class B engineering bricks are more common than class A bricks. They are both commonly a smooth red colour although blue engineering bricks are also widely available.

Common bricks

Despite their name, common bricks are actually the least common brick types in the UK. They tend to have lower compression strengths than facing bricks or engineering bricks and are generally lower quality. There is also less focus put into a consistent appearance on common bricks. Common bricks are generally used for internal brickwork only.

London stock brick

London stock bricks are a type of handmade brick used for a majority of building work in London. Its distinctive yellow colour and soft appearance come from yellow clay. London stocks are still made in comparatively small quantities in traditional brick works. Red stock bricks are also quite common, but the yellow or brown coloured bricks are usually known as London stocks. This brick is usually manufactured in Essex and Kent. They are made from clay composed of sand and alumina to which some chalk is added. The manufacturers grade the bricks as 1st hard, 2nd hard, and mild.

Stock bricks

The term stock brick can either indicate the common type of brick stocked in a locality or a handmade brick made using a stock. A stock or stock board is an iron-faced block of wood fixed to the surface of the moulder’s bench. The brick mould fits over the stock; the brick maker fills the mould with prepared clay and cuts it off with a wire level with the top of the mould; before turning out the ‘green’ brick onto a wooden board called a pallet for drying and frying.