Basement waterproofing – Don’t Smother It – Uncover It !

Premier Heritage were contracted to undertake a detailed measured survey and prepare / design a specification of works to provide a basement water proofing system beneath a detached Grade II Farmhouse 

New floor ready for sump pump

New floor ready for sump pump

The client had previously contacted several building contractors / water proofing specialists all of whom put forward specifications that involved covering the walls with water proofing membranes and cementitious slurries.

This semi basement was an integral part of a domestic dwelling but was largely unusable due to its limited head height and extremely un-even floors, made up of concrete and flags stones, the latter of which were mainly unsalvageable for reuse.

Perimeter drainage installed and sump pump fitted

Perimeter drainage installed and sump pump fitted

To make the project viable and following a full survey it was decided that the finished floor level could be reduced by at least 300mm, although this would potentially create a risk of flooding as the floor would be lowered close to the existing water table. The client also expressed a desire to maintain the aesthetic finish of the exposed stone walls internally, which whilst damp were not considered to be a potential point of water ingress.

Having put forward a design and guideline costs and following consultation with our appointed structural engineer and the local conservation department, works commenced, which initially involved digging out and reducing the existing floor levels, reinstatement of a new floor slab incorporating a perimeter drainage system, sump and pump to remove excess ground water. This design also allowed that; – in the event of any water ingress above the finished floor level, that this would run safely down the walls and into the floor drainage system.

Membrane laid over the floor slab

Membrane laid over the floor slab

The exposed stone walls were raked out, cleaned and re-pointed using a lime based mortar, ‘which allows the walls to breathe’ and finally the entire floor was over laid with salvaged flagstones obtained from local reclamation yards.

With improved passive / mechanical ventilation and heating this basement is now in full use as a family room, gymnasium, and office, but more importantly whilst works have incorporated modern methods of water management and materials, the conservation approach taken in retaining the exposed stone walls and flagstone flooring has maintained the character of the property, without the loss of or covering of historic fabric.

The finished basement

The finished basement

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