BS8102 v BS8576 Top Trumps. John Naylor Technical Director

Transcription

1 BS8102 v BS8576 Top Trumps John Naylor Technical Director

2 Reminder of Ground-Gas Hazards

3 Site Investigation Boreholes Monitoring Laboratory analysis Weeks to Months Risk Assessment Desk Study Conceptual Site Model Gas Protection Process Consideration of gases and vapours Generic GSV Detailed assessment Assigning Characteristic Situation Installation Design & Specification Proportionate to the risks posed BS8485 Points Scoring System Ventilation Structure Membrane BS8102 Considerations Verification NVQ Level 4 Qualification CIRIA C735 Verification Plan Integrity Testing NVQ Level 2 Installation Qualification Independent Protection from Follow on Trades

4 BS8102:2009

5 BS 8485:2015 Updated from the 2007 standard and first published June 2015 Heavily used by industry (including regulators) Undergoing review for amendment to BS8485:2015+A1:2018 Consultation closed on the 19 th August 2018 Expect amendments in early 2019

6 BS8485:2015 Characteristic Situations CS1 Very Low Risk No special precautions required CS2 Low Risk Passive Gas Protection (<30m span) CS3 Moderate Risk Highest level of passive protection and limit for private unmanaged residential dwellings CS4 Moderate to High Risk Lower active systems for commercial and industrial. Managed residential possible with care. CS5 CS6 High Risk Very High Risk Large industrial sheds with large open areas. Really think about it. Yes even here you can develop, but should you be building on it?

7 BS8485: Building Types & Sensitivity Source: Table 3 from BS8485:2015 Can have different types in the same building Requires Professional Judgement

8 BS8485: Scoring Determine your minimum score requirements using a combination of two or more of the following elements: Ventilation measures (pre-structural barrier or membrane!) Structural barrier or basement Gas-resistant membrane You can t add extra points for using the same element twice!

9 BS8485: Gas Protection Score, Table There are several additional notes to this table You may consider different parts of the building requiring different scores The blue background denotes a possible change of text to BS8485:2015

10 BS8485: Table 5 Structural Barrier C) The score is conditional on the waterproofing being provided by a suitable structural barrier with the design and detailing of the walls and floor meeting the requirements for [BS8102:2009] Type B protection. The score cannot be assigned for Type A (waterproof membrane) or Type C (drained cavity wall). D) If a membrane is installed beneath and around the basement to provide Type A waterproofing (BS8102:2009), it can be assigned a gas protection score in accordance with Table 7, if it meets all the criteria for a gas resistant membrane in that table. A geosynthetic clay liner used for waterproofing is unsuitable as a ground gas barrier.. The blue background denotes a possible change of text to BS8485:2015 Why?

11 BS8485: Table 5 Structural Barrier C) The score is conditional on the waterproofing being provided by a suitable structural barrier with the design and detailing of the walls and floor meeting the requirements for [BS8102:2009] Type B protection. The score cannot be assigned for Type A (waterproof membrane) or Type C (drained cavity wall). D) If a membrane is installed beneath and around the basement to provide Type A waterproofing (BS8102:2009), it can be assigned a gas protection score in accordance with Table 7, if it meets all the criteria for a gas resistant membrane in that table. A geosynthetic clay liner used for waterproofing is unsuitable as a ground gas barrier.. The blue background denotes a possible change of text to BS8485:2015

12 BS8485: Table 7 Amendments Expanded to include both the gas resistant membrane and joining products Beefed up minimum membrane requirements for mass per unit area and resilience including thickness measurements made between any reinforcement scrims ISO methane permeability test remains, requiring products to have a methane transmission rate of <40ml/day/m 2 /atm however, materials with a greater transmission rate can be used if supported by a quantitative assessment for the particular membrane in the particular use

13 Ventilation The principle means of controlling gas concentration before it gets to the structure or membrane barrier. From simple pressure relief to active positive pressure you can score between 0.5 and 2.5 points under BS8485:2015 An exception to this rule is for carparks, where the ventilation requirements for dealing with exhaust gases are such that this would effectively deal with a significant ground gas hazard by itself and gets you 4 points Waterproofing uses ventilation methods for improving the internal air quality of the building. Note that this is not the same as gas protection as this is post structural and membrane barrier, so can t be applied in the same way to achieve points under BS8485:2015 However, the use of mechanical internal air ventilation for low level exposure of chronic risk ground-gases could be considered for: Radon Low Level Carbon Dioxide (<0.5%) Selected Low Level VOCs?

14 Use of Type C Waterproofing Systems Afraid not for methane and carbon dioxide applications! Annex A, Clause A.4 Basements using Type C waterproofing protection (i.e. drained cavities) might pose an unacceptably high risk on sites affected by ground gas. Infiltrating water might contain dissolved gas and/or contain organic compounds that can degrade to form methane and/or carbon dioxide The blue background denotes a possible change of text to BS8485:2015

15 What Next? BS8485 minor text update due soon? BS8102 update? Should ground-gas hazards be thought through in more detail? Concrete is poorly understood in the gas protection industry does this needs to change? Ventilation systems could be used more widely for a range of hazardous gases for the management of Indoor Air Quality? Independent verification of waterproofing measures? The Basement Information Centre has formed a group of interested stakeholders and a guidance document is currently in draft covering this subject

16 Code of Practice for the protection of below ground structures against water from the ground Code of Practice for the design of protective measures for methane and carbon dioxide ground gases in new buildings SPECIAL Keeping you dry POWER 64% TOOL OF CHOICE Water Resistant Coating 78% SKILL CSSW 90% SPECIAL Saving lives POWER 64% TOOL OF CHOICE Gas Resistant Membrane 78% SKILL NVQ Level2 and Level 4 90% ARCH Follow-on Trades ENEMY 15% ARCH ENEMY Follow-on Trades 15% GGS Limited 2018 GGS Limited 2018 Play to the strengths, work them together

17 Oh, and don t forget.. Health & Safety The Management of Health and Safety at Work Regulations 1999 The Construction (Design and Management) Regulations 2015 Confined Space Regulations 1997 Dangerous Substances and Explosive Atmosphere Regulations 2002 Ionising Radiation Regulations 2017

18 Thank you! Contact: or general enquiries: