CONSTRUCTION MATERIALS AND BUILDING ELEMENTS

Construction Materials and Building Elements

Construction Materials and Building Elements

Answer 1

Load-bearing Foundations

Load-bearing construction has become the most popular form of construction in the United Kingdom, with load-bearing strength masonry walls being built onto concrete foundations. These are constructed so as to spread the load (weight) of the building over the entire footprint of the property. The weight of the roof is spread, therefore, via the load-bearing walls of a property directly to the foundations. If too much weight is placed on part of a building that is not directly connected to the foundations, collapse can occur.

Load-Bearing in Cavity Walls

It is worth noting at this point another important but little-known fact that, in most domestic cavity wall constructions, it is the internal skin of the wail that bears the weight of the building. Every wall that can be considered structural, e. holding something up, or retaining something, needs a foundation. If you are simply putting a few bricks in a circle to provide a garden feature, no foundation is necessary. In all cases, the wall you are building is only as strong as the surface it is placed on. A wall built on soil will not stay in position long even if it is only holding back a few inches of gravel in your driveway (Energy Resource Center, 1995).

Foundations of any kind are designed in relation to the load they have to carry and the type of ground they are in. The minimum thickness of any type of foundation is 150 mm, the most common thickness, in solid ground, is 225 mm. However, these days foundation trenches are often filled to the top with foundation concrete as much as 1 m deep (see the explanation of trench-fill foundations later in the section). Tables giving foundation requirements can be seen at www.planningportaLgov.uk the government website for planning permission and building regulations.

Strip Foundations

A strip foundation is quite simply a strip of concrete placed in a trench. The absolute minimum thickness of this strip is 150 mm, even for DIY work. Although a foundation of only 100 mm may be enough to carry the weight of your garden wall, it will not be thick enough to stop it cracking when the ground moves.

There are occasions, such as when a garden wall is to be placed on sloping ground, where it is impossible to achieve the required thickness of concrete on a level plane for the required length. It is then permissible to place a step or steps in this foundation, which then becomes known as a stepped foundation (a strip foundation that has steps in it when required). The depth of the step is usually dictated by the rise or fall of the wall, but the same rule applies as for strip foundations: the concrete must be a minimum of 150 mm deep, so from the top of one step to the bottom of the next step must be at least twice the thickness of the concrete, or a minimum of ...