A five-year-old house in Borehamwood, Hertfordshire, suffered an ingress of blackwater in the kitchen, caused by a blocked drain.
We were called to the property where our aim was to evaluate the moisture levels in the affected part of the property, and to complete air and water sampling. We carry out air sampling following a blackwater leak to check the levels of contaminants in the air, while water sampling checks potential sources of potable water for contamination.
The evaluation of moisture levels was based on a visual inspection and where possible, a non-invasive moisture survey to identify locations of moisture and moisture migration from the incident.
The affected property is a two-storey, modern double-fronted house which was built approximately five years ago. It is compromised of a kitchen/diner, lounge, study, four double bedrooms, three bathrooms and a garage.
The internal walls are built of blockwork and drylined using the dot and dab method. The kitchen floor consists of sand cement screed and judging by the age of the property, we expected to find thermal insulation between the screed and damp proof membrane. We believed that the floor to the rest of the property is a suspended timber construction with a subfloor void underneath.
We were advised by the client that blackwater had entered the property via the sink waste and spread horizontally through the kitchen and into the hallway, WC, study, and lounge. As a result, water damage occurred to floor coverings, skirting boards, and the lower walls. The occupants were moved into alternative accommodation due to the damage.
As part of our inspection, we carried out a non-invasive moisture survey in the affected areas. At the time of our visit, atmospheric readings read as:
|Relative Humidity||Temperature||Dewpoint||Specific Humidity||Vapour Pressure|
Moisture readings taken from sample points around the property ranged from 100% WME and 999 REL to much lower readings as we reached the lounge (as pictured below).
The Technical Part
A primary area of concern was defined following in-depth moisture surveys which highlighted high moisture levels. To adequately and efficiently dry these areas, focused restorative drying was recommended.
The first steps were to complete enabling work which aims to mitigate identified risks and safety hazards. The environment is made safe, with proper access and egress identified.
In addition to focused drying, a thorough decontamination was required to make the areas safe for the occupants to return home. Sanitation of the floors needed to be done before the drying commenced to remove contaminants and prevent them becoming airborne and further distributed throughout the rest of the property.
Removal of the base fitted kitchen cupboards, skirting boards in the affected areas, kitchen floor tiles and adhesives, self-levelling compound, and laminate flooring and underlay in the hallway, study and lounge was required to aid in the drying process.
The drying process was expected to take three weeks.