Topic C1 Superstructures - walls

Functions of a wall Transfer loads from the building to the foundation (load-bearing walls) Resist heat transfer Reduce sound transmission Provide shelter Provide security Partition internal spaces Provide fire resistance

Cavity masonry wall Advantages include: Bricks are made from clay. Clay is a readily available material in the UK There are lots of qualified bricklayers in the UK Masonry cavity walls are very strong and durable, so a brick building will last a long time. Cavity walls stop driving rain getting into the inner wall surface. Brick and block work are good sound insulators. The cavity is filled with insulation so it has a lower u value than other types of walling. This keeps the building warm in winter and cool in summer. No need for external rendering.

Disadvantages include: Bricklaying is a ‘wet’ construction method. This means that the mortar needs time to dry out between ‘lifts’ Bricklaying is a slow building process. Good supervision is needed to make sure the quality of work is of a good standard. If blobs of mortar get into the cavity it can create ‘bridges’ that allow moisture to get inside the building Bricklaying cannot be done in heavy rain or if the temperature is below freezing. This slows down the construction process in winter. All openings need a vertical damp-proof course

Timber frame Advantages include: Fast construction. The walls, floors and roofs are made in a factory and then transported to site to be put up. Semi-skilled operatives can erect the outer shell – no need for highly skilled craft workers on site. Timber is a sustainable material and can be sourced in the UK. The structure can be weather tight within days, so first fix work can start more quickly than in a masonry structure. The prefabrication off-site means less waste produced on site. Disadvantages include: Expensive Poor sound insulation compared to a masonry cavity wall structure Exterior needs cladding with material such as brick, rendered blockwork or slate Poor fire resistance.

SIPS SIPS are Structural Insulated Panels. They are made of two skins of oriented strand board, (OSB) or stirling board with an expanded polystyrene core. They are pre-insulated so there is no need to cut insulation materials on site, reducing wastage SIPS are used for exterior walls, flooring and roof structures. They are ligher than masonry structures so less concrete is needed for the foundations of a SIPS structure Sketch a cross section through a SIPS wall panel

Advantages of SIPS Can be used for walls and roofs Very good thermal insulation Fast construction time – saves energy during construction phase. Rigid surface for fixings. SIPS are made to the size and shape required. This includes window and door openings and can include service ducts. First fix work can begin inside the building much sooner than a masonry cavity wall structure. Larger internal space to be created within the building. Disadvantages of SIPS Poor sound insulation compared to masonry cavity wall Exterior needs cladding Similar in cost to a timber frame structure.

Wall openings Wall openings include doorways and windows. Their function is to provide: ventilation access natural light security aesthetics

Lintels A lintel is a load-bearing component that spans openings in a wall and supports the weight of the masonry above doors and windows. In cavity walls a galvanised steel lintel is used. These steel lintels prevent moisture travelling across the cavity. They are also pre-insulated to stop thermal loss. The shape of the lintel acts as a DPC. lintels can also be a decorative feature above fireplaces or doors and windows.

Sill This is the section that the windows sits on. It takes the water away from the bottom of the window and the wall.  Sills must be waterproofed from all directions by a DPC all around them. Sills must be angled away from the house so that the water can’t run down the wall.

Cavity trays Cavity Trays are found above window and door openings and at all interruptions to the cavity such as lintels, air bricks and meter boxes. They ensure any water running down the cavity is directed out through weep holes.

Weep holes Weep holes - To drain water from cavity trays, weep holes should be provided by either installing plastic weep hole vents or by leaving gaps in the mortar perpends. Weepholes should be positioned in the first course of masonry above a cavity tray at 450mm (max) centres (at least 2 weepholes per opening).

Internal walls Internal walls can be made of timber stud construction, metal stud or solid brick. Internal partitions are either load-bearing or non-load-bearing. Load-bearing partitions help to distribute the loads of the building down to the foundations. They are usually constructed of brick or blocks. Non-load-bearing partitions carry their own load and any attached fixtures and fittings. They can be removed to allow the internal structure of the building to be changed without any structural work. Timber stud partitions are often used for non-load-bearing partition walls.

Metal stud walls Easy to move - In commercial buildings, the inside walls need to be easily reconfigured for new tenants. Metal studs make this much easier because they are lightweight and do not need foundations. - they usually have pre-moulded holes to make it easier to install wiring. - sturdy but lightweight framework for plasterboard to be fixed. This is a quicker method of installation and cheaper than using timber batons because parts slot or crimp together.