Listed property Marylebone

Case Study / Waterproofing 

Listed property in Marylebone

Waterproofing the lower ground floor level to optimise space

Listed property Marylebone

A stunning property in London’s Marylebone was recently undergoing major refurbishing. Along with the external stabilizing works, this 600sqm private residential property needed a complete revamp of the lower ground floor level. Maximizing the existing space is crucial in very central London and there was an opportunity to turn the damp, unused lower ground floor level into habitable space.

The client was hoping that the flat-roofed vault spaces at the Lower Ground level could be eventually used for ancillary and infrequent habitation including climate-controlled wine storage, steam and sauna, storage, and plant space. The main contractor working on this project OLF Construction recommended MacLennan to the Mayfair architect Arkle Boyce for waterproofing works. MacLennan had worked with OLF on previous similar waterproofing projects in the area.

Waterproofing Listed property
Waterproofing Listed property
Waterproofing Listed property


After surveying the property in person, MacLennan senior surveyor concluded that because the Lower Ground Floor is below ground level it is at risk of water ingress and should therefore be waterproofed. The existing structure hadn’t historically had water ingress issues however when designing waterproofing you need to future-proof the building. The change can occur due to a change in the behaviour of the ground water, blocked street drainage or a burst water main, just to name a few potential issues. If the below level would not be waterproofed appropriately, all refurbishing works could be at risk of being damaged if they would not be protected. Waterproofing was required to the main body of the house at this level also.

Given this is an existing structure the best solution for the inside of the below ground level was to use the cavity drain waterproofing system for minimal impact to the listed building with drainage and sumps and pumps to get rid of any potential water ingress. Areas of flat deck/terrace such as the under-pavement areas and Garden would were treated with MacLennan’s liquid applied waterproofing coating Polyprufe.


MacLennan installed waterproofing to the Listed building in Marylebone, London to make most use of the existing space turning unused space into wine cellar / steam room, sauna and all important storage and plant room space.

The work was carried out in the agreed time frames and within budget. MacLennan guaranteed the work, and it was all covered by our 10million PI.

Waterproofing deck
waterproofing concrete steps
Waterproofing deck

3d Details

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