Standards for repairing basements and flooded buildings

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This section provides benchmark repair strategies for common flood damage scenarios in domestic properties. It covers the basic elements of construction and , where appropriate, suggests a range of measures that can be taken to improve the flood resistance of new and existing buildings that might be vulnerable to repeat flooding.

The construction methods and materials used for domestic buildings vary considerably and many older properties need the knowledge of a qualified building surveyor to specify and oversee repair strategies.

fig63 Plates show the levels that flooding has reached at this UK city location.

Hence, the guidance which follows, will be most applicable to domestic buildings built after 1930. For buildings that predate 1930 and those of non-traditional construction methods the advice of a qualified building surveyor is recommended.

The resilient repair options to improve the flood resistance of new and existing buildings follow guidance provided in the document Preparing for floods issued in 2011.

= = Standards for repairing flooded buildings = =

External walls -- external finish

[Flood damaged element; Brickwork, face blockwork and stonework; Unpainted render, smooth, roughcast, pebbledash, tyrolean; Painted finish - on various render backgrounds; Tile hanging, mathematical tiles, cedar shingles, pre-finished panels, PVC-cladding]

[Benchmark repair strategy:

Pressure cleaning and making good pointing if required

Pressure cleaning if required

Pressure cleaning -- repainting required

Cleaning manually with low pressure hose and brush]

[Issues to consider

Pre-flooding condition of materials and pointing

Pre-flooding condition of render

Aesthetics

Entrapped moisture c beneath impervious coatings

Bonding

Substrate

Corrosion of fixings

Entrapped moisture]

[Resilient repair option N/A; N/A Microporous coatings can be considered N/A]

External walls -- structural element

[Flood damaged element:

Solid brickwork or stonework construction of various thicknesses

Cavity brick or block work construction of various thicknesses and materials

Timber framed construction

Chalk-clay, cob or mud walls

System built properties of precast reinforced concrete or steel frame]

[Benchmark repair strategy:

Controlled and monitored drying

Stripping out internal finishes and insulation to facilitate controlled and monitored drying

Allowing to dry with natural ventilation and seeking immediate advice from surveyor

Seeking immediate advice from qualified building surveyor]

[Issues to consider:

Solid walls may suffer from pre-flood dampness and never achieve 'dry condition'

Type of insulation within cavity

Silt entry to cavity through a Seeking immediate advice from qualified building surveyor

Submersion in floodwater can result in significant loss in strength or collapse

Corrosion of metal components and fixings

Deterioration of insulation]

[Resilient repair option:

Considering water resistant coatings externally to 500mm above flood line

Ensuring airbricks sleeved and cavity fully sealed where air bricks and services penetrate walls Reconstructing with traditional materials and methods

Reconstructing with traditional materials and methods, subject to controls

Specialist moisture repelling coatings

Self-draining insulation]

External walls - insulation:

[Flood damaged element:

Cavity brick, stone or block with urea formaldehyde foam or blown fiber insulation cavity fill Cavity brick, stone or block with closed cell foam or self-draining mineral wool batts cavity insulation Solid masonry with external insulation of self-draining mineral fiber batts or rigid plastics behind cladding Solid masonry with internal insulation behind plaster boar linings Timber frame walls with mineral wool or other insulation ]

[Benchmark repair strategy:

Seeking immediate advice from qualified building surveyor

Controlled and monitored drying

Stripping out plasterboard and removing insulation if of water absorbent type

Removing internal linings insulation to facilitate and e controlled and monitored drying of timber frame.

Seeking advice from surveyor]

[Issues to consider:

Entrapped moisture

Deterioration of insulation

Corrosion of wall ties and insulation fixings

Corrosion of insulation fixings

Entrapped moisture

Contamination of insulation

Corrosion of fixings

Existence of embedded timber grounds in masonry

Deterioration of the external sheathing panels reducing racking resistance

Damage to breather membrane]

[ Resilient repair option:

Closed cell insulation foam

Stainless steel ties and fixings

Stainless steel fixings

Stainless steel fixings

Low absorption insulating boards or semi-rigid self draining mineral wool batts]

External walls, and internal walls and partitions - internal finishes

[Flood damaged element: Gypsum plaster directly applied to masonry a background

Lime based plaster on a cement-sand rendered d background over masonry

Plasterboard on adhesive dabs applied to masonry or fixed to timber studwork

Timber strip, sheet of veneer paneling

Ceramic tiles on cement-san rendered background over masonry

Paint finish: emulsion, eggshell or gloss; Wallpaper]

[Benchmark repair strategy: Removing plaster to 500mm above flood line

Controlled and monitored drying following removal of affected decorative finishes

Removing affected plasterboard

Removing and replacing

Washing off and re-grouting if required with a water resistant grout

Washing down and removing loose and flaking finish.

Repainting

Removing and replacing when new plaster thoroughly dry]

[Issues to consider:

Visible joint between new and old plaster

Bonding of old plaster

Loss of bonding

Visible joint between new and old plasterboard

Continuity of vapor barrier a on timber frame where partial removal

Salvaging paneling in historic buildings for re-fixing after drying

Substrate

Insulation

Services

Integrity

Entrapped moisture beneath certain impervious finishes

Temporary micro porous paint finish to allow plaster to dry before re-papering]

[Resilient repair option:

Water resistant render and lime based plaster or hydraulic lime coatings

Fixing boards horizontally where re-flooding likely to allow for easier partial replacement. Not suitable for timber frame

Waterproof adhesives and grout

Microporous paints

Avoiding vinyl wall coverings]

Internal walls and partitions

[Flood damaged element:

Timber stud partition with plasterboard

Timber stud partition with lath and plaster, or lime and horse hair plaster Masonry walls with gypsum plaster finish

Masonry walls with lime based plaster finish on cement and sand render

Metal framed partitions with plasterboard sheets or faced gypsum panels]

[Benchmark repair strategy: Controlled and monitored drying following removal of w affected decorative finishes

Controlled and monitored drying of timber.

Replacing lath and plaster with plasterboard

Removing plaster to 500mm above flood line

Controlled and monitored drying

Controlled and monitored drying following removal of affected decorative finishes

Replacing plasterboard or gypsum panels]

[Issues to consider: Condition of timbers or other works may make replacement more economic Condition of timbers or other works may make replacement more economic

Visible joint between new and old plaster

Bonding of old plaster

Loss of bonding

Corrosion of metal frame and fixings]

[Resilient repair option:

Preservative impregnated timbers; plasterboard sheets horizontally

Preservative impregnated timbers and plasterboard sheets horizontally

Water resistant render and lime based plaster or hydraulic lime coatings]

Floors:

[Flood damaged element

Vinyl floor tiles or sheet vinyl floor covering submerged

Quarry tiles submerged

Solid concrete floor submerged

Suspended timber floor with chipboard

Suspended timber floor with softwood tongued and grooved floorboards

Oak blocks set in bitumen on solid concrete floor slab

Modern 'thin section' hardwood block or wood strip floors including parquet Suspended concrete floor of beam and hollow block construction]

[Benchmark repair strategy

Cleaning or replacing

Cleaning and monitoring drying

Cleaning or replacing chipboard if damaged.

Controlled and monitored drying of structural timbers

Cleaning or replacing floorboards if damaged.

Cleaning, repairing or replacing

Repairing or replacing

Cleaning and monitoring drying]

[Issues to consider

Substrate

Duration of flooding

Type of floodwater

Aesthetics

Substrate

Insulation

Services

Integrity

Entrapped moisture

Type of floodwater

Access may be required to clean silt from flooded void

Access to void beneath]

[Resilient repair option

Consider relocating services

Replacing with solid floor

Replacing with marine plywood

Replacing blocks with screed and floor finish (e.g., carpet)

Replacing with screed if on concrete floor and covering

Considering relocation of services]

Joinery and fittings:

[Flood damaged element

Painted softwood or treated hardwood external door

Double glazed hardwood patio doors or window units

Double glazed PVC-U patio doors or window units

PVC-U external door Wooden window frames submerged in floodwater

Cellular type internal doors

Timber staircase of softwood or hardwood submerged in floodwater Built in wardrobes and cupboards submerged in floodwater

Fitted kitchen units submerged in floodwater

Skirtings, door linings, architraves and trims of MDF or small section softwood

Skirtings, door linings, architraves and trims of large section softwood or hardwood]

[Benchmark repair strategy:

Cleaning and repainting or replacing if warped.

Overhauling or replacing ironmongery

Cleaning and allowing to dry out before assessing damage.

Replacing glazing units only if seals have failed

Cleaning and replacing glazing units only if seals have failed

Cleaning and replacing glazing units only if seals have failed

Cleaning and allowing to dry out before assessing damage.

Replacing double glazed unit only if seals have failed

Replacing

Cleaning and allowing to dry out before assessing damage.

Repairing with strengthening to treads or replacing

Replacing

Unless of solid hardwood and high quality, removing and replacing

Replacing

Controlled and monitored drying, removing paint finish, priming and redecorating]

[Issues to consider:

Considering cost of replacement against salvage where of modest standard

Corrosion of fixings, runners and ironmongery Corrosion of fixings, runners and ironmongery

Corrosion of fixings, runners and ironmongery Pre-flood condition of windows

Shrinkage of glue blocks may cause squeaking when dried out

Some stairs may have MDF treads and risers

For high quality, purpose-made hardwood joinery, considering specialist restoration N/A

Joinery might require removal for other trades but could be salvaged if economic]

[Resilient repair option:

Replacing with PVC-U unit

Selecting units with stainless steel fittings and ironmongery

Staircases of solid timber construction below flood level

Building off floor using plastic legs

PVC-U units

Building off floor using plastic legs

PVC-U units Hardwood or PVC-U N/A]

Electrical services:

[Flood damaged element:

Electrical installation comprising PVC sheathed cables, sockets, switches and fuse boards submerged in floodwater

Fixed electrical appliances submerged in floodwater

Electrical metering equipment in contact with floodwater]

[Benchmark repair strategy:

Immediate advice to be sought from qualified electrician.

Presumption for c replacing all components in contact with floodwater

Should be replaced

Electricity supply authority to be contacted immediately ]

[Issues to consider:

Remaining installation may R not comply with current c regulations and be condemned

Moisture may affect other components]

[Resilient repair option:

Raising sockets and routing cables above flood line can be considered

Repositioning equipment above flood line can be considered]

Gas installation:

[Flood damaged element:

Gas service pipes and apparatus in contact with floodwater

Gas fire (wall hung or floor mounted) submerged in floodwater]

[Benchmark repair strategy:

Electricity supply authority to be contacted immediately and its advice acted upon

Should be replaced]

[Resilient repair option:

Repositioning equipment above flood line can be considered Repositioning boiler above flood line can be considered]

Central heating - wet system:

[Flood damaged element: Steel panel radiators in contact with floodwater

Pipe work and apparatus in contact with floodwater Boiler (floor or wall mounted) submerged in floodwater]

[Benchmark repair strategy:

Radiators to be cleaned and repainted

Equipment to be cleaned and sanitized

Any electrical components to motorized valves or controls replaced, and insulation replaced Should be replaced]

[Resilient repair option:

Repositioning boiler above flood line can be considered]

Sanitary ware:

[Flood damaged element:

Vitreous china sanitary ware submerged in floodwater

Bath of pressed steel, cast iron or plastic submerged in floodwater MDF or chipboard base vanity unit ]

[Benchmark repair strategy:

To be cleaned and sanitized

To be cleaned and sanitized

Whole of vanity unit to be replaced]

[Issues to consider:

May need removal to facilitate other works

Salvage may be uneconomic

Removal to facilitate other works

Salvage and storage may be uneconomic

Plastic bath may have chipboard frame]

Drainage:

[Flood damaged element:

Underground drains and sewers backed up with floodwater]

[Benchmark repair strategy:

Debris and silt to be flushed through to remove.

Conduct CCTV survey if blockages encountered]

[Issues to consider:

Pre-flood condition of surface water drainage and sewerage systems]

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Updated: Saturday, February 22, 2020 11:01