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A cavity wall is a type of wall that has an airspace between the outer face and the inner, usually structural, construction. . [1] The skins typically are masonry, such as brick or cinder block. Masonry is an absorbent material that can retain rainwater or condensation. One function of the cavity is to drain water through weep holes at the base of the wall system or above windows. The weep holes provide a drainage path through the cavity that allows accumulated water an outlet to the exterior of the structure. Usually, weep holes are created by leaving out mortar at the vertical joints between bricks at regular intervals, by the insertion of tubes, or by inserting an absorbent wicking material into the joint. Weep holes are placed wherever a cavity is interrupted by an horizontal element, such as door or window lintels, masonry bearing angles, or slabs. A cavity wall with masonry as both inner and outer vertical elements is more commonly referred to as a double wythe masonry wall. [2]
Cavity walls were first used in Greco-Roman buildings, but fell out of use until the 19th century, when they were reintroduced in the United Kingdom, [3] gaining widespread use in the 1920s. [4] In the 20th century metal ties came into use to bind the layers together. Initially cavity widths were narrow and were primarily implemented to reduce the passage of moisture into the interior of the building. The introduction of insulation into the cavity became standard in the 1970s and then required by most building codes in the 1990s. [5]
A tie in a cavity wall is a used to secure the internal and external walls, typically using metal tie straps or truss-like assemblies of welded wire that link the masonry thicknesses together. [4]
A cavity wall is composed of two masonry walls separated by an air space. The outer wall is made of brick and faces the outside of the building structure. [6] The inner wall may be constructed of masonry units such as concrete block, structural clay, brick or reinforced concrete. [6] These two walls are fastened together with metal ties or bonding blocks. [7] The ties strengthen the cavity wall.
The water barrier is a water-resistant membrane, either applied to the inner side of the cavity as a film or as a troweled or sprayed liquid.
The flashing component is important. [8] Its main purpose is to direct water out of the cavity. Metal flashing usually extends from the interior wall through the outer wall and a weep hole with a downward curve allows the water to drain. Flashing systems in cavity walls are typically located close to the base of the wall, so that it will collect the water that goes down the wall.
Weep holes are drainage holes left in the exterior wall of the cavity wall, to provide an exit way for water in the cavity.
Expansion and control joints do not have to be aligned in cavity walls. [9] [ page needed ]
In modern cavity wall construction, cavity insulation is typically added. This construction makes it possible to add a continuous insulation layer between the two wythes and, vertically, through the slabs, which minimizes thermal bridges. [9] However, industry recommendations, often mandated by building codes, typically require that a cavity wall maintain at least a 1-inch (2.5 cm) drainage space free of masonry elements or insulation. [10]
Cavity wall insulation is used to reduce heat loss through a cavity wall by filling a portion of the air space with material that inhibits heat transfer.
During construction of new buildings, cavities are often partially filled with rigid insulation panels placed between the two components of the wall
In the United Kingdom, grants from the government and from energy companies are widely available to help with the cost of cavity wall insulation. The Affordable Warmth Objective (HHCRO) provides help for low income and vulnerable households to improve the energy efficiency of their properties and reduce heating bills. [11]
Government led research led to the development of advice on the installation of insulation, the definition of local rain exposure zones, and the creation of British Standard BS 8104 in 1992 that sets out the calculation procedure for assessing exposure of walls to wind driven rain to guide the installation of insulation. [12] [13]
A significant number of properties that had the insulation installed by successive UK government-backed schemes were installed incorrectly or were unsuitable for the property. [14] Incorrectly installed cavity wall insulation (CWI) causes water to seep into a property's walls, causing structural problems and damp patches that may also manifest into mould. In some cases, the damp and mould resulting from CWI can cause health problems or exacerbate existing conditions, particularly respiratory conditions. This has led to the formation of the Cavity Wall Insulation Victims Alliance (CWIVA). On 3 February 2015 the CWIVA took the debate to the houses of parliament discussing the cavity wall insulation industry. [15]
Breathing performance; early cavity wall buildings exchange moisture readily with the indoor and outdoor environment. Materials used for repairs must be selected with care to not affect the materials' breathing performance. [16]
Cavity wall insulation installed in older buildings can create problems with moisture retention. [16]
Thermal mass cavity walls are thick walls. These help stabilize the interior environment of a building better than thinner modern walls. [16]
Environmental Influences: The orientation or design of a building may affect the performance of different façades on a building. Some walls may receive more rainwater and wind than others depending in their orientation or protection to some of the faces. [16]
Moisture is one of the main problems in materials weathering. [16]
Masonry is the craft of building a structure with brick, stone, or similar material, including mortar plastering which are often laid in, bound, and pasted together by mortar. The term masonry can also refer to the building units themselves.
In building design, thermal mass is a property of the matter of a building that requires a flow of heat in order for it to change temperature. In scientific writing the term "heat capacity" is preferred. It is sometimes known as the thermal flywheel effect. The thermal mass of heavy structural elements can be designed to work alongside a construction's lighter thermal resistance components to create energy efficient buildings.
Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, wood, and even twigs and leaves, have been used to construct buildings and other structures, like bridges. Apart from naturally occurring materials, many man-made products are in use, some more and some less synthetic. The manufacturing of building materials is an established industry in many countries and the use of these materials is typically segmented into specific specialty trades, such as carpentry, insulation, plumbing, and roofing work. They provide the make-up of habitats and structures including homes.
Siding or wall cladding is the protective material attached to the exterior side of a wall of a house or other building. Along with the roof, it forms the first line of defense against the elements, most importantly sun, rain/snow, heat and cold, thus creating a stable, more comfortable environment on the interior side. The siding material and style also can enhance or detract from the building's beauty. There is a wide and expanding variety of materials to side with, both natural and artificial, each with its own benefits and drawbacks. Masonry walls as such do not require siding, but any wall can be sided. Walls that are internally framed, whether with wood, or steel I-beams, however, must always be sided.
A concrete block, also known as a cinder block in North American English, breeze block in British English, concrete masonry unit (CMU), or by various other terms, is a standard-size rectangular block used in building construction. The use of blockwork allows structures to be built in the traditional masonry style with layers of staggered blocks.
This page is a list of construction topics.
Natural building or ecological building is a discipline within the more comprehensive scope of green building, sustainable architecture as well as sustainable and ecological design that promotes the construction of buildings using sustainable processes and locally available natural materials.
Insulating concrete form or insulated concrete form (ICF) is a system of formwork for reinforced concrete usually made with a rigid thermal insulation that stays in place as a permanent interior and exterior substrate for walls, floors, and roofs. The forms are interlocking modular units that are dry-stacked and filled with concrete. The units lock together somewhat like Lego bricks and create a form for the structural walls or floors of a building. ICF construction has become commonplace for both low rise commercial and high performance residential construction as more stringent energy efficiency and natural disaster resistant building codes are adopted.
Exterior insulation and finish system (EIFS) is a general class of non-load bearing building cladding systems that provides exterior walls with an insulated, water-resistant, finished surface in an integrated composite material system.
A building envelope or building enclosure is the physical separator between the conditioned and unconditioned environment of a building, including the resistance to air, water, heat, light, and noise transfer.
Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beams, and wall panels, floors, roofs, and piles. In contrast, cast-in-place concrete is poured into site-specific forms and cured on site.
Structural dampness is the presence of unwanted moisture in the structure of a building, either the result of intrusion from outside or condensation from within the structure. A high proportion of damp problems in buildings are caused by ambient climate dependent factors of condensation and rain penetration. Capillary penetration of fluid from the ground up through concrete or masonry is known as "rising damp" and is governed by the shape and porosity of the construction materials through which this evaporation-limited capillary penetration takes place. Structural damp, regardless of the mechanisms through which it takes place, is exacerbated by higher levels of humidity.
Damp proofing in construction is a type of moisture control applied to building walls and floors to prevent moisture from passing into the interior spaces. Dampness problems are among the most frequent problems encountered in residences.
Building insulation materials are the building materials that form the thermal envelope of a building or otherwise reduce heat transfer.
A thermal bridge, also called a cold bridge, heat bridge, or thermal bypass, is an area or component of an object which has higher thermal conductivity than the surrounding materials, creating a path of least resistance for heat transfer. Thermal bridges result in an overall reduction in thermal resistance of the object. The term is frequently discussed in the context of a building's thermal envelope where thermal bridges result in heat transfer into or out of conditioned space.
The tie in a cavity wall is a component used to tie the internal and external walls —constructed of bricks or cement blocks—together, making the two parts to act as a homogeneous unit. It is placed in the cavity wall during construction and spans the cavity. The ends of the tie are designed to lock into the mortar. Also incorporated into the design of the tie is means of preventing water transfer from the outer to the inner leaves. In flat ties, this can be a twist. In wire ties, this can be corrugations formed in the wire or again a twist.
Masonry veneer walls consist of a single non-structural external layer of masonry, typically made of brick, stone or manufactured stone. Masonry veneer can have an air space behind it and is technically called "anchored veneer". A masonry veneer attached directly to the backing is called "adhered veneer". The innermost element is structural, and may consist of masonry, concrete, timber or metal frame.
A weep, a weep hole, or a weep-brick is a small opening that allows water to drain from within an assembly. Weeps are located at the bottom of the object to allow for drainage; the weep hole must be sized adequately to overcome surface tension.
A rainscreen is an exterior wall detail where the siding stands off from the moisture-resistant surface of an air/water barrier applied to the sheathing to create a capillary break and to allow drainage and evaporation. The rainscreen is the cladding or siding itself but the term rainscreen implies a system of building. Ideally the rainscreen prevents the wall air/water barrier from getting wet but because of cladding attachments and penetrations water is likely to reach this point, and hence materials are selected to be moisture tolerant and integrated with flashing. In some cases a rainscreen wall is called a pressure-equalized rainscreen wall where the ventilation openings are large enough for the air pressure to nearly equalize on both sides of the rain screen, but this name has been criticized as being redundant and is only useful to scientists and engineers.
The infill wall is the supported wall that closes the perimeter of a building constructed with a three-dimensional framework structure. Therefore, the structural frame ensures the bearing function, whereas the infill wall serves to separate inner and outer space, filling up the boxes of the outer frames. The infill wall has the unique static function to bear its own weight. The infill wall is an external vertical opaque type of closure. With respect to other categories of wall, the infill wall differs from the partition that serves to separate two interior spaces, yet also non-load bearing, and from the load bearing wall. The latter performs the same functions of the infill wall, hygro-thermically and acoustically, but performs static functions too.