Monitoring the drying process of water-damaged buildings and wet basements

This section reviews methods for monitoring the drying process, ultimately leading to a certificate of drying which is considered an essential part of the restoration program. It also presents examples of a completion report covering repair work to the building for inclusion with a building user's manual and a report for a Home Information Pack.

Monitoring equipment

There are many different types of proprietary equipment available [2] and different methods used to measure both air conditions and the material equilibrium moisture levels. The most widely used are hygrometers, resistance (or conductance) meters and calcium carbide meters. Other equipment also includes infrared thermal topography. Obtaining accurate moisture meter readings is rarely easy.

Hygrometers

To measure air conditions a thermal hygrometer should be used. This instrument measures both temperature and relative humidity (RH). The importance of undertaking this exercise is to ensure that the best drying conditions are achieved which in turn allow an optimum evaporation process to take place and are also critical in insuring that secondary damage doesn't occur.

Relative humidity exceeding certain levels could promote mould growth.

The accepted RH for mould growth is 60% RH, but can be as high as 70%.

Resistance meters: The dry condition of many materials (e.g. wood, bricks and concrete) acts as an insulator. This means that the materials will not conduct electricity in their dry state -- they have high resistance. As moisture is introduced into a material it increases its conductivity and allows a small electric current to pass through it. The greater the amount of moisture in the material the easier it becomes to conduct electricity. Therefore the measurement of electrical resistance is an indicator of moisture content in the material.

There are many different resistance meters available; but whatever meter is chosen, the most important factor is that it's used by a person who is fully trained and understands how to operate it, takes readings that are as accurate as can be obtained and then interprets them correctly.

Calcium carbide moisture measurement method . The calcium carbide, pressure based measurement method is a test where the free water in a sample is converted to an acetylene gas by mixing the sample with calcium carbide. The sample of the material is obtained using a drill. It is then weighed and inserted into the calcium carbide meter. The calcium carbide powder is added ensuring that both the test material and the calcium carbide don't mix before the tester is sealed. The resulting test provides a quantitative assessment of moisture content as a percentage of the wet weight of the drilled material.

Further information on different methods for testing both air and material moisture levels is given in the publication, A review of testing for moisture in materials

Certificate of drying

Presenting a certificate of drying to the property owner is recommended when drying operations have been completed; it's good practice and ultimately removes uncertainty about responsibility for the resulting condition of the property, if there were to be any unresolved issues. Ideally, only a technically competent person should issue the certificate.

Shown is a form of words for a certificate of drying based on Damage Management wording.

Damage Mgmt members are entitled to use the Association’s recommended wording provided they adopt its agreed standards and protocols. It is prudent for suppliers of all kinds to agree specific warrantee and guarantee wordings with their liability insurers to avoid later misunderstandings.

A certificate should be included in any building user’s manual which exists.

A “CERTIFICATE OF DRYING”?

The damage management contractor certifies that drying works required as a result of the event at the property and carried out by the contractor are now, in the opinion of the contractor, completed in accordance with agreed good practice which states that a building may be considered dry, following water damage, when: the internal conditions are at, or better than, normal room conditions the moisture on and in the building materials will not support active growth of mould and mildew.

Property at which event occurred:

Customer name:

Type of event:

Contractor reference number:

Date of event:

Date contractor completed drying works:

Date contractor completed any additional works:

This certificate of drying works is given in good faith by the contractor on the following basis: the contractor has attended the property and taken moisture readings in all areas identified by the contractor as having been affected.

This certificate does not cover pre-event dampness or water damage. It has been assumed by the contractor that the customer, or representative of the customer, has provided relevant information relating to the history of the property and in particular any previous problems with dampness or water damage events, and that these are listed below together with any apparent signs of such matters observed by the contractor (who has not carried out a full survey of the property).

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Report of flooding event

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A caveat! It is emphasized that the content of this guide does not, in its own right, provide sufficient technical information to allow a certificate of drying to be issued for which a greater degree of technical knowledge is required.

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Once the repairs have been completed, a report which identifies the issues involved, what was carried out, and any further problems likely to arise should be presented to the owner for their immediate information and for including in the building user's manual, if they have one. It should also be made available to future owners.

An example of a form for the report is shown below.

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REPORT OF FLOODING EVENT for inclusion in the Building User's Manual and /or the Home Info/Specs Sheet or Web page

Address of the property details of the flooding event outline of the event, significant dates, specific features of the event affecting the structure and fabric of the building repairs and renovations following the event details of the scope of repairs and renovations undertaken recovery measures details of methods used for drying the building fabric and timescales. Details of moisture readings flood mitigation measures details of any measures that have been taken to prevent or minimize a reoccurrence of flooding (eg installation of a sump pump, flood warning and adjustment of external levels) photographs provide digital photographs if available of damage and any key items of repair (eg damp proofing treatments, insulation, dry lining and drainage sumps).

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Report of repairs to flood damaged property :

Also, as part of the remediation process, a report should be prepared describing the work that has been done to restore the building to its pre flooding condition - a suggested format is shown opposite. This report should, again, be included in the HIP for any future sale process, and in the building user's manual, if one exists.

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Following the flooding of the building at on renovation has been carried out to restore the structure and fabric to a sound condition.

Elements of the structure describe in detail the elements of the structure affected by the event, the measures taken to restore them, any special materials or treatments used and manufacturers' recommendations. Provide materials literature where appropriate:

• Walls (external)
• Walls and partitions (internal)
• Ceilings
• Floors
• Joinery (external)
• Joinery (internal)
• Staircases
• Finishes (external)
• Finishes (internal) address date report of repairs and treatment of a flooded building

Insulation :

• Roof (external)
• Roof (internal)
• External features
• Boundary walls
• Paving
• Outbuildings
• Electrical
• Gas
• Water
• Heating
• Drainage
• Specialist installations

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Where appropriate the report should also contain details and certification of:

• biological decontamination (e.g. of sewage overflows)
• insect infestation: diagnosis and /or treatment
• fungal attack (including moulds): diagnosis and /or treatment
• asbestos: in situ and sites from where asbestos removed.

Also:

• that moisture content remaining will not have adverse effects on decorative and construction materials, and on contents generally
• that moisture content remaining will not encourage fungal or insect attack or other deterioration.

The contractor in charge of drying the building can't be held responsible for any dampness or water damage that occurs due to reconstruction, reinstatement or redecoration works carried out after it has completed the drying work.

The contractor's opinion regarding the acceptable levels of dryness within the flooded property is based on the assumption that moisture sensitive materials will not be used in any redecoration or refurbishment process. If these materials have been used, moisture barrier products should have been installed before applying any coverings (e.g. under wood laminate floors).

This report relates to drying operations arising from a flooding event and not to any inherent or pre-existing problem or matter at the property which could result in dampness or water penetration. This includes (without limitation) concrete floors, party walls, defective damp proof courses, ground floor voids and columns, cellars and basements, inadequate ventilation, production of excess moisture from normal household activities or unsatisfactory building methods resulting in condensation.

DETAILS AND CERTIFICATION OF ANY REPAIR WORK CONCERNING INSECT OR FUNGAL ATTACK, ASBESTOS, ETC.