Building Boundray Seperation - Assignment Example

BUILDING BOUNDARY SEPARATION Name Course Professor Date Part A When designing a building, the designer has to factor in multiple unfortunate incidences such as fires that may occur within it. This is because buildings are rarely built in isolation and once there is a fire outbreak in one, it can easily spread to any nearby buildings. The designer therefore has to ensure that such a situation does not occur and in case of fire, it is confined within the walls of one building not only for safety but also for easier management. There are several regulations which govern how the way architects and civil engineers can develop buildings to guarantee the safety of nearby ones. Designing for fire safety is dictated by Part B4 of the Building Regulations (UK Government, 2006, 34). The clause contains all the laws that must be adhered to in order to design a building whose walls and distance from the neighboring structures are capable of confining fires. This paper presents a detailed review of the standard guidance for England and Wales. Where Space Consideration needs to be made The space between buildings is one of the major recommendations included in the building regulations. This is a primary concern for both building designers and owners due to the important role that it plays in fire safety. There are several reasons which determine where space considerations need to be made. According to BR 187, one of these is to factor in the purpose of the building and the risk of fire occurring associated with it. For instance, there are those which are used for housing highly flammable substances and hence in the event of fire it might spread faster. This is something that the designer has to have in mind so as to provide sufficient spacing between it and other buildings to avoid the fire from escalating further. Architects and engineers always have to put in mind the occupants of a building before it is constructed. The spacing between it and adjacent ones has to be such that it is large enough to provide means of escape. When fire erupts in a building, the first priority always has to be facilitating the movement of occupants to a safe place. If inadequate space is not allocated, then a stampede might occur when they are escaping. Furthermore, the occupants may be injured from burns or suffocated by the smoke in such a situation. It is therefore necessary to factor in the approximate number of occupants that will be in the building at any one time when doing the designs. When fire erupts in one or more places within a building, one of the first courses of action that should be taken is to alert firefighting and rescue personnel. This means that the distance separating the affected building and the other ones should be large enough to allow for the easy passage of their vehicles. BS 9999 specifies that the access ways need to be broad to accommodate fire engines as well as ambulances and police vehicles. If this is not the case, they will have a hard time gaining access to the building and hence may be unable to quickly put out the fire or save lives. Finally, buildings are always designed to prevent fires from spreading beyond the compartment it originates from or causing substantial damage, however intense they are. This is because it is easier to manage it if it is confined to one area in addition to posing a lower risk to people and property. That is why the regulations provide for guidelines that are aimed at providing sufficient space to allow for easy containment of fires (‘Building Research’, 1991, 2). This is done by considering not only the type of building in question but also the kinds of fires that are likely to develop in them and how the manner in which they spread. Taking such a multi-faceted approach guarantees that the buildings are spaced at a safe distance from one another. Boundaries The boundaries that exist between one building and another are some of the most important factors when designing for fire safety as stipulated in BR 187. They refer to the structures that separate one building from another such as walls, hedges, and fences. On some occasions, no boundaries exist between buildings especially if they are within the same property or are located in an urban center. Irrespective of whether they exist or not, the regulations dictate that a designer must always consider the characteristics of boundaries that may have an impact on the fire safety of the building they are designing (Technical Handbook, n.d., 3). One of these is the boundary distance. This refers to the horizontal length from the external wall to the boundary. It is one of the most important variables as it affects multiple factors such as the spacing between buildings and the maximum allowable spacing. Normally, the owner of a piece of land commissions construction of a building within a specific site. This area is encompassed by a site boundary beyond which they might not necessarily have control over. As per the building regulations, their operations are confined within this boundary save for when permit for additional works is obtained. Properties usually border several others and hence they might have multiple boundaries. When designing for fire safety, not all might be considered. The ones which are factored in are referred to as the relevant boundaries. Assessment of Space Separation Assessing the space separation between buildings is one of the primary roles of regulators in accordance with BS 9999. In addition to this, they have to check whether the present unprotected areas are allowable. These are the parts of an external wall which by design cannot attain the desired duration of fire resistance. They are therefore less secure than the rest of the building and hence their positioning and numbers are determined by the building regulations. There are two different techniques through which this can be done: (a) The Enclosed Rectangle Method This is also referred to as the geometric method and involves using geometric principles as outlined in the regulations to assess the space separation and whether the unprotected areas are allowable or not. It is mainly used when the external wall of the building or compartment being analyzed is one meter or more away from the boundary. To do the assessment, the assessor follows the following steps before getting the final outcome: 1. Firstly, a plane of reference along which all the measurements and calculations will be based upon is established. The most suitable one is located in such a way that it touches most of or an entire side of the building and is approximately parallel to the boundary. It should also under no circumstance pass within the building or cross the boundary under consideration. However, it can pass through balconies and other projections that form a part of the building. Sometimes, the distance from the boundary is not set and hence an assumed one is used for computations. 2. Perpendicular lines are projected from the reference line extending to the unprotected areas that have been proposed in the plan. Their maximum alignment to this reference line should be 80 degrees. A rectangle enclosing all the projected unprotected areas is then constructed. 3. The regulations come with tables listing standard rectangle sizes for different kinds of buildings or compartments. An appropriate rectangle whose height and width are either equal or greater to those of the constructed one is selected 4. The total area of the protected and unprotected areas are then calculated and the percentage of the unprotected area derived by expressing this area as a percentage of the relevant enclosing rectangle 5. For designs where the boundary distance has been set, the allowable unprotected percentage from the boundary is read from the table. If the value of the calculated one is greater than this one, and the design appropriately modified. This process is repeated for all sides of the building. 6. For designs where the boundary distance is not set, the minimum allowable distance to the plane of reference on all sides of the building is read from tables based on the unprotected percentage. This gives the location of the boundary. In situations where the plan is superimposed with these minimum distances, a buffer zone beyond which the boundary must not encroach is established. (b) Protractor Method This technique is alternatively known as the method of aggregate notional areas. Its approach is quite different from the preceding one in that the building is viewed specific points along the boundary. From these, the total effective area of the unprotected areas is calculated. The overriding concept is that those unprotected areas which are closer to the boundary are more effective or notional than the farther ones and hence they have a greater multiplication factor. These factors are determined by the use of a protractor whose scale is similar to that of the plan. It is placed on the design and the unprotected areas falling on different zones are assigned with corresponding factors. The total notional area is obtained by summing the products of the actual area and the appropriate multiplication factor. The maximum aggregate notional area should never exceed the value spelt out in the regulations. The process is undertaken in the following steps: 1. The sides of the building on which the unprotected areas are to be located are first identified. Once this is done and the relevant boundary is known, the testing points on the boundary are then determined 2. Not all unprotected areas have to be considered and hence only the relevant ones should be determined and calculated. Finally, the total notional unprotected area is obtained by their summation. (c) The Simple Geometry Method This is another technique commonly used in the determination of unprotected areas and does not involve as much geometric interpolations as the previous one. The regulations provide restrictions on the characteristics of buildings whose unprotected zones may be calculated using this method. They should either be office, residential or class 2 factory buildings whose heights do not exceed 9 meters. If these conditions are met and the maximum length from any side of the building to the boundary is 24 meters, then the unprotected area is obtained by the product of this length and six. Its simplicity makes it one of the easiest methods of obtaining the unprotected area in a fast, accurate and efficient manner. PART B Before the JB Firth building is constructed, it has all the prerequisites as per the building regulations have to be met. These include the inclusion of the unprotected areas. This should be done with consideration to the two other buildings in its proximity within this site. Utilizing the enclosed rectangle method, the calculations are done as follows: Scenario 1 To obtain the necessary values, one of the assumptions that are made is that the compartmentation is as shown on the site. In the case of building 1, there is no compartmentation and hence the calculations are done with regard to this scenario. The dimensions of the rectangle enclosing are given as follows: Design Width, Wd = 29.9 m Design Height, Hd = 16.3 m From tables for this type of office building, the closest rectangle to this one has the following dimensions: Tabular Width, Wt = 30 m Tabular Height, Ht = 18 m Therefore, area of enclosing rectangle, Ar= 30*18 = 540 m2 Using the dimensions of the different compartments, the total unprotected area, Au can be calculated as follows: Au = [(3.5*2) + (2*2*10)] + [(2.4*3.5*3)] + [2.5*2.4*30] = 252.2 m2 Expressing the total unprotected area as a percentage of the unprotected area yields: Au / Ar*100, % UPA = (252.2/540)*100 = 46.7 % This can be rounded up to 50%. Therefore, the minimum distance from the relevant boundary can be read from the tables on the 50% column hence yielding: Allowable UPA distance = 9.5 m Scenario 2 The second slide provides one type of compartmentation for the second building. The same process as the one used in calculating the allowable UPA for the other building can therefore be utilized here too. Wd = 27.4 m Hd = 2.4 m Ar = 27.4*2.4 = 65.76 m2 From the tables, Wt = 30 m Ht = 3 m Hence, Au = 30*3 = 90 m2 % UPA = 65.76/90*100 = 73%. This is rounded down to 70% From the tables again, the allowable UPA distance = 3.5 m Scenario 3 This is essentially the same building as 2 with the only difference being on the way it has been compartmented and hence providing different parameters for use in the calculations. Wd = (27.4 -1.4) =26 m Hd = (5.1 + 9.2) =14.3 m Ar = 26*14.3 =371.8 m2 From the tables, Wt = 30 m Ht = 15 m Hence, Au = 30*15 = 450 m2 % UPA = 371.8/450*100 = 83%. This is rounded down to 80% From the tables again, the allowable UPA distance = 11.0 m Scenario 4 This presents another different way of compartmenting the second building and provides a wide range of possibilities on which one to use in the calculations. By taking into consideration the lower left zone only, the following computations can be made: Wd = (27.4- 3.5) = 23.9 m Hd = (2 +1 ) = 3 m Ar = 23.9*3 = 71.7 m2 From the tables, Wt = 24 m Ht = 3 m Hence, Au = 24*3 = 72 m2 % UPA = 71.7/72*100 = 99.6%. This is rounded up to 100% From the tables again, the allowable UPA distance = 4.5 m Similarly, the calculations can be done by considering the right lower zone only. This leads to the following computations: Wd = (3.5 +0.7) = 4.2 m Hd = 2 m Ar = 2*4.2 = 8.4 m2 From the tables, Wt = 6 m Ht = 3 m Hence, Au = 6*3 = 18 m2 % UPA = 8.4/18*100 = 47%. This is rounded up to 50% From the tables again, the allowable UPA distance = 2.0 m Moving forward, it is also necessary to make the same calculations for the upper left zones since it is also encompassed by an enclosing rectangle. This is done as follows: Wd = 27.4 m Hd = 10.6 m Ar = 27.4*10.6 = 290.44 m2 From the tables, Wt = 30 m Ht = 12 m Hence, Au = 30*12 = 360 m2 % UPA = 290.44/360*100 = 80.6%. This is rounded down to 80% From the tables again, the allowable UPA distance = 9.5 m Finally, the calculations are made for the remaining zone. This is located on the upper right side of the elevation and hence the calculations can be made in the following manner: Wd = 4.2 m Hd = 10.6 m Ar = 4.2*10.6 = 44.52 m2 From the tables, Wt = 6 m Ht = 12 m Hence, Au = 6*12 = 72 m2 % UPA = 44.52/72*100 = 62%. This is rounded down to 60% From the tables again, the allowable UPA distance = 4.0 m Methods of Increasing the Allowable UPA for the Elevation of the JB Firth Building Whenever the allowable UPA can be increased, it should be done. This is because it enhances the fire safety of the nearby buildings as in the event of fire within the building under consideration it will be less likely to affect the others. There are different techniques that can be used to increase the allowable UPA for this elevation of the JB Firth building (Planning Portal, n.d., 1). Some of these are mentioned in this section. One way is by enhancing the fire rating of the external walls. If fire breaks out within the building, the last line of defense before it approaches the boundary and eventually the neighboring buildings are these walls. It is therefore necessary to factor them in when the architect or civil engineer has the intention of increasing the minimum allowable unprotected areas. The materials being used in the construction of the walls should be such that their fire rating makes them capable of meeting the required safe duration. The building regulations provide for materials with different fire ratings and hence it is the designer’s responsibility to select the most suitable ones. Another thing that can be done is enhancing the fire protection and compression systems within the building. These include devices for detecting any possible sources of fires and providing warnings. Furthermore, installing more fittings such as automatic overhead sprinklers would come in handy as they stop the fire before it spreads and becomes uncontrollable. If these are placed in the right manner throughout the building, then they would be capable of preventing fire from spreading beyond the walls. Once this has been done, then the allowable UPA can be increased since the threat of fire moving beyond the confines of the building would be significantly diminished. It can also be done by altering the occupancy or occupant load of the building. The JB Firth building has a high occupancy due to its mixed usage, offering not only laboratory facilities but also office space. The designers in partnership with the university’s administration can come up with a way of reducing its occupancy at any one time. Alternatively, how occupants are distributed within the building can also be adjusted to provide the most secure alternative. Doing this will help in reducing the possibility of fires caused by human errors while easing their access to escape routes. This therefore enables the designer to create a larger allowable UPA since they will be doing so for a building which is more secure as far as fire safety go. Finally, another thing that can be done is shifting the usage of the building. According to the building regulations, the fire safety of a building largely depends on what it is used for. The laboratories within the building reduce its fire safety since they may contain hazardous and highly flammable chemicals. The designers might therefore consider restricting its usage to exclusively office space. Fires are less prone to occur in offices in comparison to laboratories. The safety of the building is therefore enhanced and it gives the designer a leeway to increase the UPA up to a reasonable degree. References Building Research Establishment Report, 1991. External Fire Spread and Building Separation Distances.[Online] (Updated Jul. 11 2015) Available at: Planning Portal, n.d. Building Regulations: Fire Safety. [Online] (Updated Jan.2 2016) Available at: Technical Handbook, n.d. Non-domestic. Scottish Building Standards http://www.gov.scot/resource/buildingstandards/2013NonDomestic/chunks/index.html UK Government, 2006. Approved Document B(Fire Safety) Volume 2: Buildings Other than Dwellinghouses. [Online] (Updated Dec. 7 2010) Available at: < https://www.gov.uk/government/publications/fire-safety-approved- document-b> Read More