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The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer

The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

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Page 1: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

The role of building flood resilience within flood risk management

Andrew Tagg

Principal Engineer

Andrew Tagg

Principal Engineer

Page 2: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 2© HR Wallingford 2005 11 April 2023

Outline

Overview and definition of resistance / resilience

Research basis for new guidance

Guidance overview

Example of resilient home

Future developments

Page 3: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 3© HR Wallingford 2005 11 April 2023

Evolution of approach to floods

“Act of God” • Accept the vagaries of nature

Man against nature• Flood defence, control or management

Recognise social and environmental dimensions• “Living with rivers”

Flood risk management • A portfolio of policies and actions • “Room for the river” (NL, 2000)• “Making Space for Water” (UK, 2004)• New EU Directive (2007)

Page 4: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 4© HR Wallingford 2005 11 April 2023

Flood Risk Management Practice

Post-flood measures

Flood event measures

Real time risk management

Pre-flood measures

Preventive risk management

Forecasting and warning, reservoir control, evacuation, rescue, etc.

Spatial planning, contingency plans,

flood defence (mitigation) measures,

insurance, preparedness, etc.

Relief, clean-up, reconstruction,

regeneration, etc.

Page 5: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 5© HR Wallingford 2005 11 April 2023

Hierarchy of flood mitigation approaches

Definitions• Flood avoidance - constructing the building in

such a way that it avoids being flooded, e.g. by raising it above flood level

• Flood resistant - constructing the building to prevent flood water entering the building or damaging its fabric. This has the same meaning as flood proof

• Flood resilient - constructing the building in such a way that minimises water ingress and promotes fast drying and easy cleaning, and does not cause any permanent damage

• Flood repairable - constructing the building in such a way that although flood water enters the building, elements that are damaged by flood water can be easily repaired or replaced

Page 6: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 6© HR Wallingford 2005 11 April 2023

Research/responses for flood mitigation

• Flood avoidance - PPS25 and use of Flood Risk Assessments to determine flood risk and inform design

• Flood resistant - testing of flood protection products via kitemark scheme (to address doorways and other openings)

• Flood resilient - recent project to address other ‘weak points’ in walls, floors, joints

• Flood repairable - wide experience from flood repair industry (‘PAS64’, ‘Standards for repair’, ‘Repairing flooded buildings’)

Page 7: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 7© HR Wallingford 2005 11 April 2023

Recent project (1)

‘Improving the flood resilience of buildings through improved materials, methods and details’Funders

• DCLG & Defra / Environment Agency with:– NHBC– Scottish Building Standards Agency– Council of Mortgage Lenders– Concrete Block Association– CIRIA Core members

Page 8: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 8© HR Wallingford 2005 11 April 2023

Recent project (2)

Consortium• CIRIA• HR Wallingford• Leeds Metropolitan University• WRc• Waterman Burrow Crocker

TimeframeJanuary 2005 to February 2007

Contributes to ‘Making Space for Water’ (Defra)

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Page 9© HR Wallingford 2005 11 April 2023

Resilience – main issues

Flood resilience• Limiting the damage• Reducing time to re-occupy• Health & safety issues – stress and the disruption

to normal lifestyle• Cost of repairs (Promoted by insurers)

Outcomes• A guidance document for key stakeholders• Methodology to incorporate methods and

techniques into the Building Regulations

Page 10: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 10© HR Wallingford 2005 11 April 2023

WP2 – Review of existing knowledge

• Reviewed experience and evidence from around the world • Very difficult to provide total flood resistance• Much of existing knowledge based on expert advice, assumptions and extrapolations • The advice is in the main derived from experience and a common sense approach• General lack of scientific experimental data• Little published scientific research into the performance of buildings and construction materials in floods, with only limited attempts to collect and analyse experiential data

Page 11: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 11© HR Wallingford 2005 11 April 2023

WP 6 (Collation & analysis of post-flood data)

• Many interviews with key groups/individuals involved in flood repair industry• Liaison with other initiatives (e.g. flood resilient house built as part of FLOWS project)• Review of new documents (PAS69, ‘Repair of flooded buildings’)• Analysis of drying data

• Largely confirms findings of WP2 review• Lack of hard evidence• Lack of agreement on definition of resilience

Page 12: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 12© HR Wallingford 2005 11 April 2023

WP5 – Laboratory tests

Testing programme:

• Stage 1 – Building materials • Stage 2 – Walls • Stage 3 – Floors • Stage 4 – Promising / Innovative materials

Page 13: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 13© HR Wallingford 2005 11 April 2023

WP5 – Laboratory tests of building materials

Test procedure (mimicking flood conditions)

Two phases:

- Wetting phase: up to 4 days (48 hours) ; testing units are exposed to still flood water 1m deep

- Drying phase: 7 days (168 hours); test units allowed to dry naturally under laboratory ambient conditions

Page 14: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 14© HR Wallingford 2005 11 April 2023

Elements testedMaterials Masonry cavity walls

Bricks: Engineering bricks (Classes A and B) Pressed Facing Bricks (sand and spike textured) Hand-made facing bricks

Empty cavity: Engineering bricks and concrete blocks Engineering bricks and Aircrete blocks Facing bricks and concrete blocks Facing bricks and Aircrete blocks Facing bricks and concrete blocks and external cement render

Blocks: Concrete blocks (3.5N and 7N) Aircrete (Autoclave concrete)

Full fill: Facing bricks and Aircrete blocks and mineral fibre insulation Facing bricks and Aircrete blocks and blown-in insulation Facing bricks and concrete blocks with mineral fibre insulation and internal lime based plaster

Timber board OSB2 11mm and OSB3 18mm thick

Part fill: Facing bricks and concrete blocks with rigid foam insulation

Mortars Below DPC 1:3 (cement:sand) Above DPC 1:6 (cement:sand)

Timber framed walls

Floors External facing bricks, empty cavity

External concrete blocks with cement render, empty cavity

External concrete blocks with lime render, empty cavity “Promising methods”

Thin layer mortar joint on solid block wall Solid masonry wall with external insulation Masonry cavity wall with external and internal renders

Concrete slabs (0.5m by 0.5m): 100mm thick, strength 32.5 150mm thick, strength 32.5 150mm thick, strength 42.5 150mm thick, strength 42.5, polythene sheet below slab - 300m overlap - Taped lap - Blockwork foundation, side wall - Blockwork foundation, side

wall, concreted trench - Blockwork foundation, corner

wall, concreted trench

Timber framed cavity wall using splash-proof plaster board

Page 15: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 15© HR Wallingford 2005 11 April 2023

Test results

Hand-made brick

Seepage through Hand-made brick

Page 16: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 16© HR Wallingford 2005 11 April 2023

Stage 2 - Testing of walls

Test rig – two identical test rigs

Page 17: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 17© HR Wallingford 2005 11 April 2023

Test results – illustrative examples

Wall ME1 (Eng Bricks on external face and Concrete blocks on internal face) during wet test

Plaster board

Page 18: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 18© HR Wallingford 2005 11 April 2023

Flood resilience characteristics

Water penetration – the seepage through the material (different from “water absorption”)

Drying ability – the capability to regain the original moisture condition

Retention of pre-flood dimensions, integrity – the lack of deformation or change in form or appearance of the material

Page 19: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 19© HR Wallingford 2005 11 April 2023

Summary information for GuidanceResilience characteristics*

Material Water penetration

Drying

ability

Retention of pre-flood

dimensions, integrity

Overall resilience

performance

External face

Engineering bricks (Classes

A and B)

Good

Good

Good

Good

Facing bricks (pressed: sand-textured, spike-

textured)

Medium

Medium

Good

Medium

Internal face

Concrete

blocks

Poor

Medium

Good

Medium

Aircrete

Medium

Poor

Good

Medium

Cavity insulation

Mineral fibre

Poor

Poor

Poor

Poor

Blown-in

Poor

Poor

Poor

Poor

Rigid PU foam

Medium

Medium

Good

Medium

Renders/Plaster

Cement render – external

Good

Good

Good

Good

Cement/lime render – external

Good

Good

Good

Good

Gypsum

Plasterboard

Poor

Not assessed

Poor

Poor

Lime plaster

Poor

Not assessed

Poor

Poor

* Resilience characteristics are related to the testing carried out and exclude aspects such as ability to withstand freeze/thaw cycles, cleanability and mould growth

Page 20: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 20© HR Wallingford 2005 11 April 2023

New Guidance

May 2007

Launched by Minister

Page 21: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 21© HR Wallingford 2005 11 April 2023

CIEF Bristol

11 December 2007

Design water depthup to 0.3m

Design water depthfrom 0.3m to 0.6m

Design water depthabove 0.6m

Approach

Attempt to keep water out‘Water Exclusion Strategy’

• Materials and constructions with lowpermeability

Allow water through property to avoid risk of

structural damage.Attempt to keep water out for

low depths of flooding

‘Water Entry Strategy’ ***

Design water depth* Mitigation measures

• Materials with low permeability up to0.3m

• Accept water passage through buildingat higher water depths

• Design to drain water away after flooding• Access to all spaces to permit drying

and cleaning

Attempt to keep water out, in full or in part, dependingon structural assessment.

If structural concerns exist follow approach above ***

• Materials with low permeabilityto at least 0.3m

• Flood resilient materials and designs• Access to all spaces to permit drying

and cleaning

Notes:

* Design water depth should be based on assessment of all flood types that can impact on the building

** Resistance/resilience measures can be used in conjunction with Avoidance measures to minimise overall flood risk

*** In all cases the ‘water exclusion strategy’ can be followed for flood water depths up to 0.3m

Remove building/developmentfrom flood hazard

Res

ista

nc

e/R

esi

lien

ce**

Avo

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• Land raising, landscaping, raised thresholds

Page 22: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 22© HR Wallingford 2005 11 April 2023

Proposed changes to Building Regulations

New requirement in Part C* - Resistance to the effects of flooding:

• An FRA/FCA – mirroring requirements in PPS 25/TAN 15• Requirement to incorporate reasonable measures to

mitigate the effects of flooding• Adequate means of refuge/escape• Safe during floods without increasing risk to emergency

services• * Site preparation and resistance to contaminants

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Page 23© HR Wallingford 2005 11 April 2023

Closing the loop between Planning and B. Regs.

Proposals to B Regs – expected to be implemented in 2008/09 – aim to close the loop between:

Planning system - key responsibility to determine whether flood effect mitigation is requiredBuilding control - responsible for its application

In practice, proof of compliance to amended Part C to be sent to LPA prior to commencement of building work

Page 24: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 24© HR Wallingford 2005 11 April 2023

Resilient House (1)

Page 25: The role of building flood resilience within flood risk management Andrew Tagg Principal Engineer Andrew Tagg Principal Engineer

Page 25© HR Wallingford 2005 11 April 2023

Resilient House (2)

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Page 26© HR Wallingford 2005 11 April 2023

Concluding remarks

• Await amendment to Building Regs. – will it happen?• Recent project on ‘encouraging uptake of resilience’• Pilot studies on resilience measures – update end May• Has new Guidance being used?

•Clear benefits from resilience, BUT- Needs incorporating into policy- Uptake for existing properties would provide greater benefits