BYTNAR - TALKS
EPISODE 020 - APPROVED DOCUMENT C - SITE PREPARATION AND RESISTANCE TO CONTAMINATES AND MOISTURE
This episode is for people who want to know more about Approved Document Part C – Site Preparation and Resistance to Contaminates and Moisure.
You should like this episode if you ask yourself questions like:
What are the key requirements of Approved Document C for site preparation and resistance to contaminants and moisture?
How do Building Regulations address construction in flood-prone or contaminated areas?
What legislation applies to contaminated land in the UK, including The Contaminated Land Regulations 2006?
How do you ensure a building site is free from hazardous materials like asbestos, radon, or sulphates?
What are the methods for evaluating building sites for contaminants and moisture issues?
Where can I find guidance on impact assessments and remediation for contaminated sites, like BRE DIGEST or NHBC publications?
What are the different types of risk assessment procedures for managing site contamination?
How can subsoil drainage be implemented to protect buildings from groundwater damage?
What construction methods help prevent ground moisture transfer in floors, walls, and roofs?
This is Bytnar Talks the Engineer Takes on Construction Episode 20 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 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 C site preparation and resistance to contaminates and moisture hi there and welcome to bitn talks your favorite podcast on all matters of architecture engineering and construction it is Thursday the lucky 13th of June 2024 and I'm here back with you with the 20th episode and information on site preparation and resistance to contaminates and moisture Yes you heard it right it's the 20th episode so that would mean that Bitner talks is now at the top of podcasters of podcast in the world not because we the best quality or talk about the the things that everyone want to listen to but we persevere and that's the 20th episode and I think we still deliver a lot a lot more anyway let's get back to the merits of this podcast and let's recap what I talk talk to you about in the last episode where I finalized talking about the approved document B volume two the fire safety in buildings other than dwellings I've mentioned fire requirement B3 which mandates that buildings be designed to maintain structural stability during an event of fire and resist fire spread between shared walls focusing on compartmentation and fire suppression systems loadbearing elements such as roofs flow and walls must meet deta detailed fire resistance standards outlined in appendix B with single story buildings generally exempt unless they support compartment structures as however there are caveats provisors and stipulations to everything so race storage areas in single story buildings may require additional protection as they may change the character of the single story building and turn it into multi-story building I told you that sprinklers are generally require re for buildings with top stories over 30 m above ground level to enhance the fire suppression cavity barriers are necessary to prevent fire spread through concealed spaces with specific guidelines for large Hidden spaces open-sided car Parks May rely on natural ventilation while closed sided car Parks need enhanced fire resistance and mechanical ventilation in compliance with standards like bs1 366 bs21 101 or BS 7346 external walls and roofs must resist fire spread considering the building's height use and position with regulation seven enforcing appropriate materials and workmanship adequate access for fire appliances and firefighters is crucial with specific guidelines for vehicle Access Fire Mains and hydrants with special consideration for buildings lacking fire Ms Mains all with extensive perimeters finally in regulation 38 which requires the provision of relevant fire safety information to the responsible person upon the completion or occupation of the building information that should include design and construction details as well as information necessary for the safe operation and maintenance of the building particularly for those under the regulatory reform fire safety order 2005 which in simple terms means nearly all buildings but single dwellings and single Flats in this episode I will move to the approved document C and the consideration for the discharge of site preparation and resistance to contaminates and moisture requirements so without further Ado let's dive into the text of the approved document C [Music] as mentioned in this episode I will talk about the statutory guidance contained within the approv document C side preparation and resistance to contaminates and moisture I will start by reading you the actual requirement as put in the building regulations which spreads the consideration into two parts Part C1 that deals with the preparation of the side and resistance to contaminants and part C2 that deals with the resistance to moisture the guidance is then further divided into section 0 to six and some general commentary and I cannot wait to tell you all about it so let us not waste any more time on fuing about and dive into it straight away shall we so here we go part C side preparation and resistance to contaminants and moisture requirements C C1 point1 the ground to be covered by the building shall be reasonably free from any material that might damage the building or affect its stability including vegetable matter top soil and preexisting foundations point two reasonable precautions shall be taken to avoid danger to health and safety caused by contaminants on or in the ground covered Oro be covered by the building and any land associated with the building point three adequate subsoil drainage shall be provided if it is needed to avoid a the passage of ground moisture to interior of the building B damage to the building including damage through the transport of water born contaminants to the foundations of the building and point four for the purposes of this requirement contaminants means any substance which is or may become harmful to persons or buildings included substance substances which are corrosive explosive flamable radioactive or toxic and of to requirement C2 resistance to moisture the walls floors roofs of the building shall adequately protect the building and people who use the building from harmful effects caused by a ground moisture B precipitation in including wind driven spray C interstitial and surface condensation and D spillage of water from or associated with sanitary fittings or fixed appliances it could not be simpler to abide by the requirement just as long as we make sure there will be no damage to the structure or the health and well-being of the occupants the requirement can be considered fullfilled it needs to be noted though that the building may require upgrading when it under goes material change of views even if it is a historical building and historical fabric may need upgrading or relocation for later rain statement so let's have a look what does the section zero got for us section zero this with General considerations such as performance if you are in the construction game you are well aware of things that can damage your building things like sulfates or the Japanese nwe and many many more can harm you as you go about living in your property eating arsoning infused kale from your patrio garden may prove not so healthy after all living in damp and moldy rooms is also not for the faint-hearted as well as sitting in the ren air whilst enjoying your favorite movie and knowingly developing cancer in your lungs is something you should be protected from there are many ways in which the structure and we Ware of the occupants in and about the building can be undermined and the guidance highlights the responsibility of designers and building and contractors to ensure the requirements of building regulations are fulfilled the guidance points us out that special consideration may be needed in flat prone areas flooding for whatever reason may be problematic some sides may be affected by contaminants and may need extended consideration of the other legislation such as the contaminated land England regulation 2006 or the Environmental Protection act act 1990 or Town and Country planning acts there are also obligation put on us when we discover contamination on our land and it includes the provision of information to appropriate agencies and gaining appropriate authorizations for the works we are about to do that leads us nicely to section one that talks about clearance or treatment of unsuitable materials in this section you will quickly find out there is a process to all that building professionals do and that no consideration starts without Gathering proper information first this process is familiar to all surveys undertaken by Engineers out there and it contains planning stage desk study walk over survey sampling and testing many of us think about the Seria sampling and tasting stage but this is the last part and cannot be done well if the previous steps are not in place and undertaken by a competent person with a well- winow experience naturally vegetation roots and turves can be problematic for the bearing capacity and behavior of structures trees in their near vicinity of structures have potential of causing damage when the soil consist of shrinkable clays the guidance references several Publications to abide by when assessing such impact or providing a solution it names bread digest 240 241 and 298 it references nhbc chapter 4.2 you can appreciate the map prepared by the guide showing the typical distribution of shrinkable soil and where to expect Less sufate in the ground Roots can cause problems in the underground drainage as well and building on Brownfield sides or on field brings about certain additional risks that also need identification for the investigation work for the appropriate approach to the design and specifications of for the building section two resistance to contaminants deals with biodegradable waste in landfills pesticides Fuel and oil spills preservatives munitions decay in biological matter and many many more can be part of your site identification of typical contaminants by the industry can be found in the dep Department of the environmental profiling of Industries guide which which rudimental list is contained within the table within the approved document the natural geology may also suggest contamination with natural occurring heavy metals or gas or with further of which further guidance can be found in the environment agency Publications about land quality in England and Wales to address solid and liquid contaminants we need to assess the risk first in the gist for the risk to be there there need to be a source of contamination pathway through which it travels like air soil or water and the receptor which can be a building structure Building Services or people in or about the building remove one of the one of these and there's no problem but you need but you need to find out what is the hazard first don't you defra and environment agency Pro procedures published in CLR 11 now withdrawn but still referenced by the approved document sets out the stages of the procedure and the approach is divided into three tiers tier one preliminary risk assessment tier two generic quantitative risk assessment and tier three detailed quantitative risk assessment like with all assessment we start light before we we go into the assessment with all guns blazing which in this case would be the tier three approach before deciding on the appropriate cause of action we need to identify possible Hazard assess the site and estimate and evaluate the risks the scale and detail of the surveys will depend on the extent of the development part of the site and the possible receptor of any particular Hazard if we need to deal with the contamination we can either treat it contain it or remove it each strategy will have its limits and cost consequences so needs to be appro approached carefully Sera Publications nhbc's and environmental agency stuff are the place to go to for further guidance special mention is given to hydrocarbons permeating polyan water pipes and the reference of guidance contained within the water research report F FR 0448 gases can be a big issue methane carbon dioxide V vol organic compounds and and other gases from landfills mines organic deposits hydrocarbon spills need to be taken in consideration often the only solution for the isolation of the receptor from the gas is by the virtue of membranes over ventilated spaces so that the gas can dissipate outdoors and does not find its way into the building similarly rodon protection measures may be required and in Pate Raiden protection membranes over naturally or mechanically ventilated samps section six subsoil drainage this section mentions consideration of the gravity soil drainage when the site is susceptible to higher water tables but not flooding as well as many other consideration when the side does get flooded to address matters like s sarging of seage or when building over the subsol draining that due consideration is given to either RAR routing and or provision of access points for cleaning sub soil drainage should be considered if the building is laid where the groundwater transports contaminants and its job is to drive this water away from the building and its services section four deals with flaws and that's is a start of requirement C2 the requirements are rather simple the floor cannot transfer the moisture from the ground to the top surface does not promote condensation or be subject to intertial condensation meaning somewhere in the buildup of the flow you will need to provide a vapor barrier insulation and the continuous dprof membrane this may be relaxed in storage spaces there are some minimum requirements for the ground bearing slabs of minimum 100 100 mm thick dense concrete under slab membrane of 0.3 mm or 300 micromet thick or otherwise called 1200 gauge whatever nomenclature you like to use and it should be laid over well compacted hardcore and a layer of blinding blinding the purpose of blinding is to remove any sharp edges from the hard code that could P penetrate that membrane DPM over the slab can be the same polyan as for the under the slap application but it can also be three layers of cold applied bmen solution or similar moisture and Vapor resistant material more involved consideration maybe for the slab subject to water pressure the suspended Timber ground floor needs to be isolated from the ground moisture by dump proof cause have a ventilated space underneath on opposite side of the building with with ventilation slots on the opposite sides of the building of minimum 1500 mm Square per met run of the external wall all 500 mm Square per M square of floor area whichever is greater and the ground needs to be leveled all or drained and covered to resist moisture and the growth of plants sometimes the ground need to be treated to kill any any unwanted vegetation underneath that that suspended floor stopping that that moisture and vegetation can be achieved by pouring 100 mm of Lin Mix Concrete over a compacted hardcoree or by laying a dum proof membrane under 50 mm of either sand or mixed concrete blinding some consideration should be given to the boarding of the floor which needs to be durable for the purpose of use like in kitchens or toilets should be more resistance to any spills than in other places of the building all the BS need need to be treated similar consideration are applicable to suspended concrete flaw in both cases heave may be an issue and may influence the amount of ventilated space underneath the floor but it generally starts with 150 mm mm of clear space all 75 mm are under the wall plates when it comes to internal or Surface condensation the document makes a reference of other approved documents like bra report 262 or information paper ip17 SL1 but gives a minimum U value of 0.7 wats per M squar Kelvin section five deals with walls like floors walls need to be constructed to stop the moisture from the ground from the outside and to mitigate on vapor and surface condensation when we talk dampness from the ground we should think of appropriate D proof CES either engineering brick slate pimen or polyethylen generally if the wall abots the ground the DPC should be 150 mm above the ground level and in case of cavity wall either have a cavity that gathers water at the base some 225 mm or three C cses of brick below below the dump Pro proof course or there should be a cavity tray that directs water towards the external Leaf external leaf with whip holes which should be provided every 900 mm or four bricks spacing if you like but at least there need to be two whip holes an end stop tray over opening when it comes to the precipitation the choices are three either a thick enough wall cavity wall or clading if the exposure to driven rain is very severe clading is the right choice for the protection of solid walls but otherwise the wall can be rendered or left bare anyhow top of walls top and bottom of openings and abutments with roofs should address the passage of moisture walls can be insulated in plethora of ways externally in cavity or internally on in all cases the moisture passage from the outside to inside and the other way around should be thought about and appropriately appropriate composition specified some details on the insulation of M mine walls in line with exposure to driven rain zone are given within the guidance clading should be robust and fulfill its function and can be imperious like metal or glass weather resistance like Natural Stone clay and wood moisture resistance like products lapped at joints or be be jointless or sealed at joints in any way it needs to perform its function a particular attention should be put on the sealing of doors and windows especially in parts of the country that suffer extreme exposure to driven rain as well as in circumstances where level thresholds are expected to facilitate uninhibited access to the building condensation issue will be generally covered if the wall achieves U value of Maximum again 0.7 wat per M Square Kelvin and the interstitial considerations are covered in British standard 5250 and 13788 section six deals with roof but it is basically but it basically rer is the previous expectations given to framed and clouded walls the limit for condensation however is set at nearly half of that of the floors and walls and it is at 0.35 wat per M Square [Music] Kelvin so this is it folks the approved document C side preparation and resistance to contaminates and M contaminates and moisture let's sum it up requirement C1 mandates that building sites be free from harmful materials precautions must be taken to avoid health and safety hazards from contaminants like corrosives explosives radioactive material or toxic substances requirement C2 ensures that the building's walls floors and roof protects against ground moisture precipitation and condensation section zero General consideration tells us that designers and contractors must ensure compliance with building regulations with special consideration given to flood flood prone or contaminated areas relevant additional legislation includes the contaminated land England regulation 2006 Wales if in Wales and a bit different Provisions for scotlands and Ireland and the EnV Environmental Protection act 1990 section one clearance or treatment of unsuitable material emphasizes forough evaluation of the site predicaments planning of the investigation starting with desk study with with planning desk study walkover survey sampling and testing guidance references the laes of building research establishment digest and National house building Council Publications for impact assessments and for providing Solutions section two resistance to contaminants mentions common contaminants including biodegr biodegradable waste pesticides and hydrocarbons and the risk assessment procedure which involves preliminary risk assessment generic quantitative risk assessment and detailed quantitative risk assessment options for dealing with contamination include treatment containment or removal with guidance from Syria nhbc and the envir environmental agency section three subsol drainage considerations include gravity Sal drainage especially in FL flat prone zones and Provisions for routing or accessing subsol drainage when buildings are built over the existing subsol drainage the goal is to direct water away from the building and its services section four flaw mentions that flaws must prevent ground moisture transfer avoid condensation and incorp operate a vapor barer insulation and a dump proof membrane ground bearing slabs should be at least 100 mm thick with appropriate polyan sheets as dump proof membranes suspended floors require ventilation of void space and isolation from ground moisture section five walls tells us the walls must prevent moisture Ingress from the ground and from the outside as well as to mitigate condensation appropriate dprof causes and cavity traes may be necessary wall construction options include solid walls cavity walls or framed clouded walls with insulation consideration for each type section six roofs must meet similar moisture and condensation resistance standards as walls and floors in the gist these requirements and sections provide General guidelines to ensure buildings are safe and resistance to contaminants and moisture protecting both the structure services and its occupants in in the next episode we will move to approve document D toxic substances to talk about the cavity insulation and move to approve document e resistance to the passage of [Music] sound I hope you enjoy this episode and that the considerations of the approved document C side preparation and resistance to contamin and moisture makes a simple sense to you right now the building control approved document guidance is pretty simple once you know why and what is required if you have any questions reach out to me on LinkedIn or send me an email I'm more than happy to help you out in BNA 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 wwwb 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 on 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 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 see you next week and remember Bytnar Designs the World Around 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.
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