Requirements for Space Separation between Buildings - Coursework Example

Fire Safety Engineering: Requirements for Space Separation between Buildings and the Issues Associated with External Fire Spread Insert (s) Course Instructor’s name Course Code Date of Submission Fire Safety Engineering: Requirements for Space Separation between Buildings and the Issues Associated with External Fire Spread 1. Introduction Fire safety is one of the most essential building regulation design requirements for any new building construction in the United Kingdom. The requirements generally cover a wide range of aspects including space separation as well as other areas related to external fire spread. Space separation between buildings is particularly important in restricting the possibility of fire spreading to the nearby buildings across the open spaces between the buildings. As a result, the contemporary building regulation design requirements stipulate the minimum distance of a newly constructed building from a notional boundary such as a road’s center line. This is particularly intended to reduce the risk of fire spreading from one building to another particularly where some parts of the external wall do not guarantee the relevant period of fire resistance or has a combustible surface material (unprotected areas). The spread of fire from a burning building to the adjoining structures or buildings may occur in various ways such as through direct flame contact, ignition of flying bands, radiative heat transfer and convective transfer of heat. Other than space separation, there are a number of other considerations that are also required to be taken in order to satisfy the requirements of external fire spread mitigation such as the structural fire resistance of the surface finish and the nature of roofing (British Standards Institution, 2011, p.29). According to the British regulations, the external wall of new buildings must be able to offer sufficient resistance to the spread of he fire over the walls as well as from one building to another, taking into consideration the position, use and height of the building. The regulations regarding space separation and allowable areas on the particular walls generally determines if a building is considered to be in a boundary condition. This paper critically reviews the requirements for Space Separation between buildings based on the UK regulations and the major issues associated with the external fire spread. 2. Functional Requirement of External Fire Spread There are a number of building regulations and requirements that are currently being applied in the UK with regard to the design and management of space separation between buildings in order to ensure that the fire safety measures are incorporated in the new building designs whenever possible. According to experts, the fire safety regulations regarding space separation are designed not only to secure the safety of persons inside and outside the buildings by minimizing the potential spread of fire from one building to another but also to allow for sufficient space for fire fighting equipment and vehicles in the event of fire outbreak. Generally, the provisions of the requirements are largely based on a number of assumptions that are designed to achieve reasonable standard of space separation between buildings. At the same time, the provisions also attempt to limit the amounts of unprotected areas within the sides of buildings particularly any openings and areas with combustible surfaces which may not be able to provide adequate protection against external spread of fire from a given building to another (ADB, 2006, p.44). Under the current Approved Document B-Fire Safety (ADB), the major assumptions of the provisions of the requirements regarding space separation between buildings include: a. The size of the fire depends on the compartmentation of a building such that a fire may occur in a compartment but will not spread to the other compartments b. The intensity of the fire is closely related to its potential and purpose c. Residential (1 and 2), recreation and assembly present a greater risk of fire spread than other building uses. d. There is always a building at the far side of the boundary with similar elevation to the building in question at the same distance from the common boundary. e. The amount of radiation passing through any part of the external wall that has got fire resistance may effectively be discounted. The current Approved Document B-Fire Safety (ADB) contains a significant number of technical guidance relating to stopping the external and internal spread of fire in the build environment as well as the possible means of escape that should be incorporated in the design. Volume 1 of the regulations particularly focuses on dwelling houses while volume 2 is primarily concerned with buildings other than dwellinghouses. Approved Document B-Fire Safety defines a dwelling house as any unit of residential occupation that is occupied by a single household (not more than six individuals), family or an individual (ADB, 2006, p.44). However, there is a gap in the contemporary fire safety regulations regarding space separation between the buildings as there is no specific standards or codes that currently provides technical guidance for the determination of safe fire separation between the buildings outside the site boundary. Generally, within any given site, the constructor is often required to control the works as well as the escape routes of the site labor. A number of guidance and supporting documents have been developed by the STA in collaboration with the Association of British Insurers (ABI), Fire and Rescue Service, Health and Safety Executive (HSE), the Fire Protection Association (FPA) and the Fire Engineers. 3. Areas Where Space Separation Need to be Considered There are three major areas in which space separation in building may need to be considered. One of the areas where space separation may need to be considered is when there is insufficient boundary condition. Generally, the regulations regarding space separation and allowable areas on the particular walls generally determines if a building is considered to be in a boundary condition. The details of relevant boundary for space separation are primarily described in the Approved document B. According to the document, buildings that have been constructed at the same site but are managed or operated by different owners must be able to comply with the space separation requirements. For example, whenever there is no sufficient structural resistance to fire in the external walls, the space separation between the buildings should be wide apart to ensure that sufficient safety against fire spread is achieved. According to experts, Space separation and fire safety inclusively enhance a provisional way for the escape from the upper parts of the floor for more than approximately 4.5m above the found level. The engineering and construction work of buildings are provisionally described in a 2.6 and 2.7 spacing ties though this may not be followed in cases where the constructions have more than one internal stairway. Additionally, floors construction in terms of spacing must structurally pave way for effective alternatives easily and spaciously separated from each other. The ideal purpose for the 4.5m benchmark of engineering constructions spacing is to ensure fire safety as well as separation by-fire resisting construction material as per the room numbers. The stairways split-up in the buildings plays a major role towards the determination of the buildings’ space separation; the space separations between buildings depending on the stairways should have a protected stairway or the top floors can be separated and given their own alternative escape rules during the designing and construction periods. 4. Details of Relevant Boundary with Explain Diagram According to various British building fire safety regulations, a relevant boundary refers to the actual boundary of a site which a wall faces. the separation between buildings is primarily measured in terms of the distance of the building to a boundary rather than the distance to another building. This is particularly important as it makes it possible to calculate the allowable proportion of the unprotected areas regardless of whether or not there is an adjoining site. Finally, although the ADB Building regulations do not impose any the design and management of any building, building designs that are based on unsustainable management regimes are considered not to have met the requirements of the regulations. Fig 1: Relevant boundary Fig 2: Notional and Relevant boundary Although roof design is not subject to the sections of the provisions regulating space separation, the provisions may be applied to roofs that are pitched at angles greater than 700 to the horizontal line. Similarly, the vertical parts of any pitched roof like dormer windows (when taken in isolation) may be regarded as a wall, and therefore does not need to meet the requirements of the provisions unless the roofs slope exceeds 700 In this regard, whether dormer windows running across a steeply pitched roof should be treated and regarded as a wall or a roof is a matter of judgment. 5. Geometric method of assessing separation and unprotected areas The simple Geometric method of assessing separation and allowable unprotected areas in a building particularly involves the use enclosing rectangles whereby a geometric rectangle is drawn around the unprotected area and the enclosed rectangle is then compared to various tables provided by BR 187. The table provided by the document particularly gives specific rectangle dimensions as well as percentage values for any unprotected area. For example, when the unprotected are is 6m2, then the expected distance to the boundary should be about 1m. 6. Aggregate Notional areas (Protractor method )  The protector method is particularly used in areas or buildings with irregular geometry where the enclosing rectangle can not be used. Although the risk of fire can never be completely eliminated, the methods of calculating building distances, the methods of calculating the separation distances of building provided in BR 187 can help to significantly delay the ignition of adjacent buildings thereby allowing for the sufficient time for the Fire service to be able to arrive on the site and take appropriate preventive action. However, the design and construction requirements related to fire safety of flats and other common buildings containing flats are addressed and dealt with under ADB2(ADB –Volume 2). The new ADB regulations have recently undergone a number of amendments and are largely based on general risk assessments rather than prescriptive building design rules. In this regard, the document places greater responsibility on the building designers to carry out detailed risk assessment regarding the operation and maintenance of buildings. BR 187 is another important publication that has effectively addressed a number of factors related to external fire spread including the British national building regulations and ways of calculating the required space separation between buildings. In addition, BR 187 supports the Approved Document B Building regulations currently being used in the United Kingdom. The publication is part of the British Occupational Health & Safety Information Service that provides a comprehensive review of regulations, legislations, guidance, standards, including the contemporary best practice fire safety measures. Finally, the BR 187 also provides sufficient theoretical background for fire safety as well as a detailed analysis of external fire spread issues, mitigation strategies as well as a comprehensive background to Methods 1 and 2 of the Approved Document B. Second attributed engineering separation attribute between the buildings is the provision of escape separation routes from the upper floors to about 5.0m above the ground level. In some buildings’ separation scenarios, a single window can be modified to serve two rooms. The interlinked separation of buildings through a one window separation frame work must have a provision of access to stair. A communicating door in between the two separated rooms must also be provided so as to give a possible access into the building through the windows in case of any emergency (Read, 2001 pg. 121). Substitute approaches to the building separation linked to the exit is the staircase separation from landing hence giving an alternative exits from the buildings. Space Separation Between Buildings on a Site: Case Study of the New JB Firth building that faces Maudland Building According to various UK standard fire safety guidance documents, the separation between buildings should be measured based on the distance of the building to a boundary as opposed to the distance to another building. This is generally important as it makes it possible to calculate the allowable proportion of the unprotected areas regardless of whether or not there is an adjoining site. Although the most UK standard building guidance and regulations do not impose any the design and management of any building, building designs that are based on unsustainable management regimes are considered not to have met the requirements of the regulations. On the other hand, the provisions also attempt to limit the amounts of unprotected areas within the sides of buildings particularly any openings and areas with combustible surfaces which may not be able to provide adequate protection against external spread of fire from a given building to another. For example, in situations where buildings appears to be closely constructed such as the case of the New JB Firth building that faces Maudland Building, ground or basement separation storey exit of a conical shapes are constructed. The ground basements easily provide well-separated boundaries between buildings. Fig 1: Ground floor of the building The ground or basement storey may also be designed to provide as exit into an enclosed space. Through the ground or inner basement storey building separations are also normally verified as per variations of various emerging emergency issues such as fire and overall evacuation plans of the buildings. The wall linings separating ground foundations of the buildings are of a thin nature in order to minimise the final outcomes of the spacing after construction. The slopes of walls must slope at an angle not less than 70 degrees horizontally (Read, 2001 pg. 140). In most buildings separations the above 70 degrees structural construction has been adopted to necessitate an appropriate spacing of these buildings. Fig 2: First floor For the first floor of the New JB Firth building that faces Maudland Building, the regulations require that the first floor of the new building is constructed in such a way that inhibits the spread of fire to the neighboring buildings in the event of fire. In this regard, the potential size of the fire depends on the compartmentation of a building such that a fire may occur in a compartment but will not spread to the other compartments. Additionally, Maudland Building at the far side of the boundary offers a similar elevation to the New JB Firth building at the same distance from the common boundary with regard to the first floor. Consequently, the amount of radiation passing through the external wall of the first floor can be discounted by calculating the allowable proportion of the unprotected areas regardless of whether or not there is an adjoining site. Second floor In the second floor, the space separation between the buildings should be wide apart to ensure that sufficient safety against fire spread is achieved. Based on the floor plan, space separation and fire safety inclusively enhance a provisional way for the escape from the upper parts of the floor for more than approximately 4.5m above the found level. The engineering and construction work of buildings are provisionally described in a 2.6 and 2.7 Finally, although roof design is not subject to the sections of the provisions regulating space separation, the provisions may be applied to roofs that are pitched at angles greater than 700 to the horizontal line. Similarly, the vertical parts of any pitched roof like dormer windows (when taken in isolation) may be regarded as a wall, and therefore does not need to meet the requirements of the provisions unless the roofs slope exceeds 700 In this regard, whether dormer windows running across a steeply pitched roof should be treated and regarded as a wall or a roof is a matter of judgment. Other Issues Associated with External Fire Spread There are a number of other important issues that are normally associated with external spread of fire namely the structural fire resistance of the surface finish and the nature of the roof coverings. Generally, the spread of fire from a burning building to the adjoining structures or buildings may occur in various ways such as through direct flame contact, ignition of flying bands, radiative heat transfer and convective transfer of heat. Other issues associated with fire include the materials used and design for the boundary conditions of buildings. Design for the boundary condition of buildings: In buildings where structural fire resistance is largely needed, there must be a boundary designed condition which is widely accepted and is necessary for fire resistance. All the boundary materials used in the building construction must support stanchions and have a fire resistance capability. This means that the construction materials such as steel should be overly fire protected and the cladding materials of the building be tested and proved to be of an insulation and integrity fire resistance functions (Wiggins, 2010 pg. 101). The walls, rafters and supporting stanchions must be protected from fire. Nonetheless, the bases of the protected stanchions should be designed in a way that they are capable and resistant to any overturning forces and momentums caused by the collapse of the unprotected building parts in case of any fire event. Economically, structural design of buildings’ boundary is one of probably economical solutions towards fire protection as an occurrence in the buildings. The engineering methods of boundary designing widely depend on calculation methods. These calculation methods are in most construction cases used to derive horizontal forces and moments created by rafter collapse of stanchion bases. Another issue associated with external fire spread between buildings is the loadbearing elements of external building structures towards fire prevention. Premature failure of structurally constructed buildings as a result of fire should not be blamed on the contactors but the loading bearing elements of these buildings. Through loadbearing construction knowledge, structures in the recent past have been tentatively verified to have maximum standards of fire resistance, in relation to collapse of failure of load bearing capacity of these structures as a result of temperature variations. The purpose of providing buildings with load bearing elements include; to reduce the risk-bearing nature of fire-fighters while they are engaged on rescue operations in the buildings (Wiggins, 2010 pg. 134). Finally, load bearing elements in buildings reduce to some degree the danger to the people exposed in the vicinity of the buildings on fire. Load bearing construction of buildings lastly ensures a minimal risk to the occupants, some whom may be faced with the problem of inability to make their own escape if they are injured or trapped in buildings under fire. Fire resistance standards applications for load bearing elements include an engineering provision to ensure that the whole structural materials used are high in melting point and gives stability to other neighbouring buildings. The supporting elements must also have an additional fire resistance constructed based on standards which are of greater and relevant fire-resistance ability. Load bearing construction finally provides a restriction to fire spread and sub-divide building compartments hence reducing the fire intensity across building structures. Conclusion In conclusion, there are a number of standard UK building regulations and requirements that are currently being applied in the UK with regard to the design and management of space separation between buildings such as ADB, 187 and BS 9999. These standards are increasingly being used in order to ensure that the fire safety measures are incorporated in the new building designs whenever possible. However, although the contemporary building regulations and requirements regarding space separation and fire safety are generally effective, there is need to develop a more holistic fire safety strategy that considers the users, the designers as well as firefighters. This is because there is a gap in the contemporary fire safety regulations regarding space separation between the buildings as there is no specific standards or codes that currently provides technical guidance for the determination of safe fire separation between the buildings outside the site boundary. References ADB. (2006). Approved Document B (Fire safety)-Volume 1: Dwellinghouses (2006 edition incorporating 2010 and 2013 amendments. London: BSI Chitty, R. 2014. (1991) BR187: External fire spread: building separation and boundary distances. Watford: BRE. British Standards Institution (2001). BS 7974: Application of fire safety engineering principles to the design of buildings. London: BSI. British Standards Institution (2011). PD 7974 -2011 Part 3: Structural response and fire spread beyond the enclosure of origin. London: BSI. Chitty, R. 2014. External fire spread: building separation and boundary distances (BR 187 2nd edition). London: Building Research Establishment. Read More