Our client, a prospective homeowner in Oxford, contracted Timberwise to conduct a pre-purchase damp survey to investigate water ingress and potential fungal decay within a property. This property was a mid-terrace property of solid brick construction, and was both occupied and furnished at the time of our inspection. The weather conditions were overcast but dry.
Challenges
Due to historic flooding and elevated water tables within the local area, the property had suffered from repeated ingress of groundwater entering the sub-floor void. The occupants had installed a pump within the sub-void to remove groundwater. However, there was still evidence of ongoing groundwater ingress into the sub-void beneath the property, indicating that the pump had either failed or was not powerful enough to remove the amount of water entering the void. Repeated water ingress can create significant problems not only with decorative elements of a property but also with structural elements such as timber floors or masonry.
Observations
To understand the issues within the property, our surveyor began by investigating the internal floor. The owner of the property had given permission to lift floorboards in two areas to inspect the sub-floor timbers.
Upon lifting timbers near the front bay window, black spot mould was identified underneath the timber flooring, as well as white mould growth on the floor joist. Our surveyor identified the likely cause as high humidity evaporation, as the timbers were near the front air vents.
Our surveyor also used an electronic conductivity meter to assess the moisture content of the nearby timbers, which revealed moderately high readings within the area. They continued taking readings on the adjacent wall, which also revealed high moisture content within the masonry. Although conductivity meters only give a true reading on timber, they can still provide an indication of a damp concern when used on plaster or masonry, and can be used to profile how far a damp issue has spread.
In the rear of the property, our surveyor measured a moisture reading of 34% from one accessible floor joist, indicating very damp sub-floor conditions. The timber had also been repaired previously, indicating previous issues with fungal decay created by the damp environment. High moisture readings were also taken on the floorboards and adjacent wall plaster.
High moisture conditions throughout the ground floor of the property were not only creating risk to the internal decorative finishes, but more importantly, the structural timbers were at risk of sinking or even collapsing if the damp issues remained unresolved. A long-term waterproofing solution capable of managing hydrostatic pressure and groundwater movement was required to protect the property from future damp ingress.
Solutions
Due to repeated water ingress and fungal decay within the sub-floor void, our surveyor recommended two possible courses of action. Either;
- Installing a new pump into the sub-floor void, as well as sub-floor fans to remove humidity from the property, or
- Installing a concrete slab in place of the timber flooring, along with a damp-proof membrane and cavity drainage system.
While the former option was more economical in cost, it also carried with it significant risk. No guarantee would be offered due to the presence of water in the sub-floor void, and the proposed renovations would only treat the symptoms, rather than the root cause of issues within the property.
The latter option was identified as the best practice by our surveyor, and would provide a complete waterproofing solution to combat hydrostatic pressure and damp ingress in the property. The solution would also fall under Timberwise’s standard guarantee period, ensuring the longevity of the solution for our client.
After taking ownership of the property, our client contracted Timberwise to install a full waterproofing system within their new property. Our surveyor designed this system to a Type C standard to ensure complete control of water ingress within the property.
Next, the timber flooring was removed, and the sub-floor cleared of any fungal material or mould to create a clean base to work from. Once cleared, our technicians prepared the floor void for damp prevention beneath the concrete slab, first by installing a layer of scalping in the sub-floor void, and then a layer of blinding sand. Both measures would provide a permeable material to drain any moisture away from beneath the slab and prevent erosion. The team then laid the reinforced concrete slab over these layers.
After a 4-day curing period, our team returned to finalise the treatment for our client. To prepare the area, our team of technicians first removed the existing wall plaster in the affected areas, which had failed due to the ingress of moisture over time. A new damp proof course (DPC) was installed on the affected walls, as it was found that the existing DPC had worn away through the consistent moisture ingress within the property. The walls and concrete floor were then lined with an anti-lime coating to protect against future damp ingress.
Once dried, our technicians installed a cavity drainage system. This was achieved by first creating a channel at the base of each wall, at then applying a damp proof membrane to each wall and the concrete slab floor. If water ingress occurred in future, this would reflect off the membrane and into the channels at the base of each wall, preventing moisture from entering the interior of the property.
Our technicians completed these measures by installing a new sump pump into the concrete floor. This was then connected to the discharge pipework from the previous failed pump to safely direct water away from the property. Due to the levels of water ingress, our technicians also installed a battery backup system, ensuring that the system would always be functional even if power were lost to the pump during outages.
As a final measure, our technicians installed a layer of closed-cell insulation followed by new chipboard flooring above the damp proof membrane, ensuring that the floor could be walked on and was also ready for any decorative flooring our client decided on.
Results
Our client was impressed with Timberwise’s expert team, both during their home-buying process and later during the installation of their damp proofing solution. They were overjoyed by our surveyor’s willingness to advocate for them while entering a stressful period during their purchase, but were also delighted by the high standard of work achieved once they had their keys in hand. Our clients are now looking forward to completing the decoration of their new home, with peace of mind that the damp issues within the property are now a thing of the past.
Do You Want Help with a Waterproofing Solution?
Our dedicated and experienced team in Oxford are ready to talk to you about your options for property preservation. Don’t hesitate to call us on 01865 389 720, or you can request a survey online.
