BYTNAR - TALKS
EPISODE 015 - APPROVED DOCUMENT B - FIRE SAFETY - PART 2 OF 4
This episode is for people who want to know more about Approved Document Part B – Fire Safety.
You should like this episode if you ask yourself questions like:
What are the means of escape requirements for dwelling houses according to Approved Document B?
How should escape routes be designed for buildings over 4.5m in height?
What are the standards for protected stairways in residential buildings for fire safety?
What accessibility criteria must escape windows and doors meet for effective fire evacuation?
How is fire containment managed in flats to ensure occupant safety during a fire?
What regulations exist for emergency access routes in apartment buildings, particularly concerning ventilation and lighting?
How are evacuation distances regulated in buildings with multiple flats, and what are the provisions for alternative exits?
What are the requirements for internal fire spread prevention in terms of material linings and flame resistance?
What restrictions are placed on the use of insulated panels and thermoplastic materials for fire safety purposes?
This is Bytnar Talks the Engineer Takes on Construction Episode 15 hi I'm Piotr Bytnar each day I help my clients plan and design building projects through Bytnar Limited a Consulting Chartered Structural Engineers practice my biggest passion and the corner stone on which I've built my business is find finding clever solutions for construction projects I am a chartered structural engineer and a bing software developer so you can rest assured that I will strive to talk about the best practices and the use of new technologies in the industry and if you're embarking on a construction project or are involved in planning designing and building the world around us you'll find this podcast useful approv document B fire safety part [Music] two hi there and welcome back to the bitnar talks your favorite podcast on all matters of architecture engineering and construction it is Thursday the 9th of May 2024 and I'm here back with you with the 15th episode and further information on fire safety fire safety will take several episodes to go through so buckle up Dorothy we going down found the rabbit hole and it is a deep one indeed last week in episode 14 I started talking about the approved document B fire safety and introduce you to volume one and its initial sections section zero and one I've mentioned that the approach to fire safety will generally follow the risk profile of the particular building assigning different purpose groups group level to different buildings in this episode so I'll carry on talking about volume 1 Purpose Group 1 a to 1 C so Flats houses with floor levels at between 4 and a half to 18 M height and houses with floors at levels under 4 and 1/2 m in height an alternative approach to approve document guidance is available and you can use fire safety engineering approach using for example British standard 7974 and anciliary published documents but the approach cannot be less safe than that of the approved [Music] documents now I'll finish talking about the requiring B1 of building regulations with concerns addressed in section two and three means of escape from dwelling houses and flats and move to requirement B2 internal fire spread Linings addressing addressed in section four of the approved documents so without further Ado let's dive into the fire safety requirements B1 and B2 as treated in the approved [Music] document now I'm on to talk about the section two three and four of the approved document B volume 1 sections that deal with the means of escape from the dwelling houses and flats as well as the internal fire spread due to Linings of walls and ceiling in this episode you will find out what to take in consideration and why and I will stop to ponder a little bit on the situation when the building changes the group from 1 B to 1 C due to the vertical extension of the house either by the creation of a full story over the existing building or changing the love space into the habitable space either by simple AIC convention or other otherwise let us start with means of escape from dwelling houses in the document you'll note a diagram showing different possibilities which generally cover the following circumstances one escape from the ground floor two escape from upper stories at Max 4 and 1/2 m above ground level three escape from the S over the 4 and a half meter limit which F fly divides consideration into the situation where when there is only one story over that limit and where there are two or more stories over that limit the guidance recognizes increasing risk with the height of the building and reduction of possible Escape alternatives for its occupants it is easy to imagine that you can jump out of the window at the ground floor or even first floor of your building but going higher of the drop will make it increasingly more difficult to evacuate an important matter to consider is inclusivity of the building you cannot expect all people or people with inhibited Mobility jumping out of Windows they can certainly be lowered down through the window at the ground or first floor but dropping such person from too high will equal men Slaughter the guidance for the ground story is either to allow habitable rooms to have direct exits through the window or door or through a hall for stories Level under 4 and 1/2 met in height measured from the ground level we can allow people will escape through direct exit window or door but if not possible there should be a protected St in place interestingly if you want to connect rooms internally like in the case of Jack and Jill bathroom only one room needs to have their direct exit if there is no provision of protected stairway stairwell both ground floors and first floors can have inner rooms if the room has direct evacuation option like an escape window knowing the rooms allowed for floors at higher levels though and what is an inner room you ask it is the room that has no other way to exit but to go through the doors leading to another room otherwise called access room it could be a basement room man cave bedrooms sharing living space generally any room but the room solely used for circulation like Vesti or porch some inner rooms are lowed like kitchen laundry or utility dressing rooms bathrooms water closets or showers or galleries within a reason and access rooms will need to have smoke alarms and and cannot be a kitchens you cannot walk through the kitchen to try to escape from another room as kitchen is one of the as one of the most certain places where the fire can start now now when we move through the threshold of 4 and 1/2 met level of the next story we need to think protected stairwell or several stairways if we have several stairways they need to be separated so that eventual incapacitation of one way of exit does not influence the other meaning either fire resistant construction between them or this one room between them that that would give you two different walls which would at the end of the day reach the requirement of fire separation if there is only one Escape stairway it needs to be protected to RI 30 construction Ray 30 construction what does that mean it means that the enclosure will need to hold for 30 minutes in respect of structure we need to stop flame and smoke and reduce heat let us do it again Ray fa where R stands for structural consideration load buing capacity of the enclosure e Integrity REM which means it remains in place to hold flame and smoke out and I insulation limits the temperature on the other side of the wall to 140° Centigrade sometimes you may choose to reduce the radiant radiant heat only and it falls under the letter letter W radiant H transmission limited to 15 KW per M Square usable when you want to divide space with glass the protected stairway should go straight to the Final Exit or could split into two alternative exit going through other rooms these rooms need to be separated with fire construction and cannot be inner rooms if there is only one story over the 4 and A2 M consideration we can cut it away from the consideration using Ray FY construction between between itself and the story under and provide alternative Escape Route in any case the protected stairwell needs to ensure its ceiling or S is protected to stop any fire spread through it for dwelling houses with two or more stories over the 4 and half limits stories at level over 7 and2 m should have an alternative Escape Route isolated from the bottom stories or a sprinkler system throughout for passenger lifts over 4 and a half met over the ground level the lift shell the lift shaft should be either within the protected stairwell enclosure or be enclosed by the fire resistant construction itself so how about the ventilation it is simple in the buildings with flow levels under the four and half limit as no special considerations are needed but when the limit is a little bit higher is reached they staircase should be isolated from the remaining of the house and any penetration should be fir stopped du in rigids in rigid steel mechanical ventilation recirculating air into the stairwell stopped upon smoke detection and warm air heating systems limited to 27° C are measured in the living room at midro height now let's get some definitions shall we what is an escape window or door well it needs to be wide or high enough to allow a man with a belly through meaning 450 mm at 1 M 10 height and of minimum 0.33 M square area going with the minimum width the opening should be at least 734 mm in other dimension this can prove difficult for obese people and people with Mobility problems I generally recommend a fully openable window whenever possible windows can have locks and child proofing but needs to remain open once open the skp should be able to reach safe distance from the house of at least the building height away from the building or height of immediate extension whichever is greater so what is the within reason requirement for galleries in the rooms first of all there is no limit on the area of the gallery if provided with alternative exit or escape window if under foreign half M level consideration in relation to the ground level or cannot be bigger than 50% of the room including stairs stairs within 7 and 1/2 M at Gallery level and 3 m away from the exit from the room if you want to evacuate through the flat roof or the balcony it needs to be safe to do so meaning Ray F construction and guarded from trips and falls and leads to story exit or EXT external Escape Route habitable rooms in basement should have escape window external door or access to protected stairway external Escape Routes are possible with limits imposed by the guidance and extra weather proofing if the stairs lead to stories over 6 m in height fire resisting construction should extend 1.1 M vertically up over the landing top Landing excluding basements to ground floor escape 1 and A2 M horizontally either side and 9 M vertically down just imagine Raging Fire how far away from that fire do you think you'll need to be to be able to pass by 1.1 1.8 and 9 M are generally good indicators well I'm not sure about the 1.1 M but sure you can crawl when you at the top the there are some additional or otherwise consideration for works on existing dwellings notably when the work is to the windows if replace need to be not worse than previously or not less than minimum required and may required installation of cavity barers when you do a loft conversion you need to make sure there is a protected ster introduced with Ray 30 fire doors E20 and when the work is on historic doors measures may be taken to attempt increase of a fire protection to E20 if the protected stairwell is open at the ground floor you need to provide sprinkler protection to open plan separate ground floor from the first floor to allow Loft occupants to exit through the first floor window when the sprinkle system does not work and and and closed kitchen with Ray fairy construction so basically it means if you have an open plan kitchen that goes on your stairwell is open with the stairwell you'll have to close that space well at least close the kitchen provide sprinkle system if you still want your have want your living space to be open for the onto the stairwell but then again you'll need to do a bit of closing up on the first story to enable all of the Loft occupants to go through the first first floor room window so quite quite involved and and it's rather more cost effective to to basically provide one unobscured and direct exit from from that LOF within the protected stairwell with Ray 30 and E20 doors [Music] off to section three means of Escape floods generally the philosophy of the approach is similar to the dwelling houses but the communal circulation areas are treated separately to the space within the flood and you can jump off the window if you can if the flow level is under 4 and A2 met in height the approach follows the the following consideration that the fire is contained to Flats but localized fires otherwise can happen no external rescue is considered there's unlikely simultaneous evacuation required stapo strategy is considered here confining fire to flood and allowing relatively little of the Heat and smoke three exit in mix use buildings separate Escape Routes should be provided expect except in special circumstances when habitable space is illary to the use of the main building and whe small the flat Arrangement follows that of the dwelling but with the Final Exit being the flat entrance in Flats where no Reliance can be made on Escape Windows the escape from any room when the hole is of Ray 30 should not be further away than 9 M or if there is no protected hallway 9 M from the furthest point of any room and there cannot be any Kitchen in the way or at least one and a half 1 1.8 m away from any esap ruit you see imagine imagine raging oil oil fire on the Hub that 1.8 m distance if that ever happened to you seems to be a good guidance to finding out if the kitchen is or is not in the way separation of living and sleeping sections of the house is also possible with addition of alternative exit when otherwise Inner Room scenario occures within the flat when evacuating the flat person should be able to change the direction of evacuation if encountering Raging Fire from some flood on the in their way this provision is generally achieved by excluding sway either by Lobby or Corridor separation Escape distance from any flat should not exceed 7 and 1/2 M for one way consideration and 30 m for two-way consideration way meaning access to protected stairwell either one or more in certain cases the travel distance may be reduced to 4 and 1/2 M protected access to the stairwell and Corridor should be ventilated to remove smoke General protection for the protected stairwell goes to raise 60 and all other protected spaces to Ray 30 with self closing those of E30 category head height should be minimum of 2 m but it's not including door frames which may be lower emergency lighting should be provided and EM emergency Roots marked refug shoots should be isolated from the escape routs and floods external staircase can be used by limited but it's limited to 6 M over ground for the only Escape staircase and 6 M over podiums of roofs if the building and that roof is also served by an internal staircase power circuits sufficiently protected and circuits required for firefighting run should run through areas of low fire probability there are further requirements for the stairs doors final exits lifts and they all follow logically and are logically tied to allow people uninterrupted exit when needed and to provide enough fire resistance in the event of fire this concludes requirement B1 means of Escape dwellings and floods now I'll tell you a little bit about the requirement B2 internal fire spread Linings so what does the legislation say requirement B2 got two points one and two one says to inhibit the spread of fire with within the building the internal Linings shall a adequately resist the spread of flame over their surfaces and B have if ignited either a rate of heat release or a rate of fire growth which is reasonable in the circumstances and point two in this paragraph internal lining means the materials or products used in Linings of any partition wall ceiling or other internal structure this essentially means no Carpets on the ceilings and walls well maybe the intention is to minimize the spread of fire through the fabric of the building internally the smoke and fumes generation floor and stairs covering and Furnishings is not considered in general all lining materials can produce High intense dripping droplets classified as D2 and can produce High emissions of smoke with high volume and intensity and be combustible however depending on the location can be the fire Class B to C O D meaning very limited limited and medium contribution to fire so circulation spaces rooms in general and garages and small rooms and garages sections for of the walls can be of poorer quality within certain limits and framing of doors and windows generally does not fall within the consideration special consideration should be given when insulated panels are used or PTF membranes use of thermoplastics is is conditioned plastic that the forms or is consumed with the rise of temperature in Windows roof lights and lighting diffusers is generally fine for class TPA rigid which extinguishes when the source of fuel is removed it's thick enough to do that or TPB with limited fire rate applications away from circulation areas and when specific limits are observed are good so perhaps at the end of the day a carpet could be hanged on the wall after the row so so here you have it approv document B section 2 3 and four under the belt section two of the document out outlines means of Escape for dwelling houses emphasizing different C areas based on Building height and layout ground floors can utilize direct exit while upper stories within 4 and a half meter of ground level may use direct exits or protected stairwells buildings over a 4 and 1/2 meter require protected stairways meeting rayy standards Escape windows and doors must meet specific accessibility criteria in section three which covers means of escape from floods the focus is on containment within units and controlled evacuation separation of living and sleeping areas enhances safety and emergency access routes must be well ventilated and illuminated evacuation distances are Reg related with Provisions for alternative exits section four requirement B2 addresses internal fire spread within buildings materials used for Linings must resist flame spread and have risen reasonable heat release rates special considerations are given to insulated panels and thermoplastic materials with restrictions based on fire resistance and application location in the next episode I will cover requirement B3 and B4 so internal fire spread structure and external fire spread Section 5 to [Music] 12 I hope you enjoyed this episode and that the consideration of fire safety escap in dwelling dwellings as well as the internal fire spread begins to make more sense to you if you have any questions reach out to me on LinkedIn or send me an email I am more than happy to help you out in betna we deal with planning designing and managing of your projects and we are always glad to facilitate a free initial consultation to steer you in the right direction visit www.b now.co and reach out to us whether your question is if we can help you with your project or what should I do we will be able to give you a piece of non obligatory advice at bitna we help our clients design and execute their dream homes or Investments if your building is falling apart we can also help investigate the reasons behind it and to provide you with an appropriate strategy design and specifications for the repair thank you again for listening please voice up your opinions I'm waiting for you on LinkedIn and I want to hear from you Toodloo!
Piotr Bytnar BEng (Hons) MSc CEng MIStructE
Chartered Structural Engineer who deals with the Architecture of buildings. His Master's Studies led him to an in-depth understanding of risk and contract arrangements in construction as well as specialist knowledge in soil mechanics.
He and his team help homeowners and property developers to design and deliver construction projects reducing waste in time and the cost. He believes that the construction project is an iterative process that can be well managed and it is best managed if all the aspects of the project definition and management are dealt with in-house or coordinated by one organisation. His team works to all stages of RIBA and ISTRUCTE stages of work and enables contractors to deliver projects on-site providing risk evaluations, methodologies for execution of works and temporary works designs.
Comments