Client: Construction Firm
Our client, a construction firm in Bishop Auckland, tasked Timberwise with designing and installing a basement waterproofing system to protect an extension from water ingress. This property was a house extension of shuttered concrete construction, and was both unoccupied and unfurnished at the time of our inspection.
Challenges
This property was sited directly next to a reservoir. As such, any design would need to be capable of handling the potential for changing water tables or localised flooding, either of which would increase hydrostatic pressure behind the wall. This moisture ingress also increased the risk of lime leeching from the concrete, which could block the internal drainage channels once the system was installed. As the extension was being built as a habitable space over two floors, controlling these measures would be crucial in ensuring the success of the project.
Observations
Our surveyors first investigated the property by examining drawings supplied by the architect during the planning process. These plans proposed a new building extension incorporating an above-ground reception room as well as a below ground basement structure. This extension would be connected to the original stone structure of the building during construction.
This construction would be completed by creating a shuttered frame, in which concrete would then be poured and reinforced. Once cured, our technicians would install the proposed waterproofing system to prevent moisture ingress into the finished rooms.
Solutions
With the proposal approved by our client, and with the concrete structure poured and cured, our team arrived on site to install the waterproofing system in the below ground area of the property.
To begin, our technicians installed an anti-lime coating to both the external and internal concrete surfaces. This would prevent lime from leaching out of the concrete, which could potentially cause blockages in the internal drainage channels, or affect the soil outside the extension, limiting the growth of grass and other plants around the extension.
Once the anti-lime coat had dried, our technicians then installed a further two layers of crystallising mineral waterproofing slurry to the external walls. This acts as a tanking solution, preventing moisture ingress into the concrete and internal walls. Asan additional measure, fillet details were installed at the base of each wall, encouraging water to flow away from the wall and preventing ingress in the joint between the interior wall and floor.
With the exterior measures in place, our technicians began installing the internal waterproofing systems. To begin, our technicians installed perimeter channels into pre-formed sections of the floor slab, at the base of each wall. These channels would collect any moisture that made its way through the wall. Jetting ports were set into each corner intersection for future maintenance, as well as a chamber to host a sump pump. This pump would expel any channelled moisture into an external waste drain.
With the drainage channels and pump system installed, our technicians installed the final measure to prevent moisture ingress. Moulded plastic cavity membranes were cut to size and installed along each interior wall and on top of the floor slab. These membranes were sealed at the joints between walls and the floor to ensure the system was watertight. These membranes could then be covered with a decorative finish of our client’s choice once work was completed.
These membranes prevent any moisture that would find its way into the basement from penetrating into the interior surface of the wall. Instead, water drips off the membrane, collecting into the drainage channels at the base of each wall, where it is then pumped off site. In this way, water is allowed to flow freely, preventing the build-up of hydrostatic pressure behind the wall, which can degrade tanking solutions over time.
Once all systems were in place, our technicians performed a final test of the pump alarm system and battery backup to ensure everything was working as expected prior to completion. This would warn our client if the pump wasn’t functioning, or allow the pump to continue working even through a power cut.
Results
Our surveyor designed a comprehensive waterproofing system compliant with BS 8102:2022, achieving a habitable Grade 3 environment for the new basement extension. Our client was delighted with the solutions provided, and was satisfied that the long-term guarantee would protect their home even from the fluctuating water levels of the adjacent reservoir. They were also pleased that our surveyors concluded a post-installation assessment, clean, and check to ensure the system’s long-term integrity.
Do You Want Help with a Waterproofing Solution?
Our dedicated and experienced team in Newcastle are ready to talk to you about your options for property preservation. Don’t hesitate to call us on 0191 204 1063, or you can request a survey online.
