The new Harley Gallery is an award winning extension to the original Harley Gallery which was originally opened in 1994. The new Harley Gallery was opened in March 2016 to house the Portland Collection which includes Masterpieces such as Michelangelo’s Madonna del Silenzio (c.1583), a rarely seen Van Dycke painting of Thomas Wentworth Earl of Strafford, the pearl earring worn by Charles 1st at his execution in 1649 and George Stubbs painting of the 3rd Duke of Portland on horseback outside the stables at Welbeck.

Delta Membrane Systems Limited were employed as waterproofing consultancy to the design team headed by Hugh Broughton Architects in London. Delta Membrane Systems Limited took care of the project from design stage to completion on site. The main contractor was Caddick Construction of Knottingley in West Yorkshire and our Delta Registered installer was Preserva CSS of Derby. Delta Membrane Systems were involved in all design consultations, product certifications, reviews, design team meetings, site meetings and delivered a successful product which exceeded expectations.

The scope of Delta Membrane Systems Limited role in waterproofing includes the main Harley Gallery structure and also the adjacent basement ancillary rooms, public conveniences, store rooms and the like.

The Harley gallery extension measures approx. 892m2 in overall floor area.


The main gallery slab is recessed below external ground level and it also houses all the environmental controls and plant machinery that is required to maintain the stringent climatic conditions required to protect the priceless works of art.

This is protected by two coats of Delta Koster Deuxan 2c polymer modified bitumen mesh reinforced and applied over smooth concrete blinding, protected by Delta GeoDrain Quattro drainage and protection membrane, which is flashed in and buried just below external ground level, using a Delta MS Profile Capping Strip.

The adjacent Harley Gallery basement wc’s and wash rooms are protected by a “combined” waterproofing system comprising of two coats of Delta Koster Deuxan 2c protected by Delta GeoDrain Quattro on the outside, with Delta MS20 cavity drainage DPM over the slab, Delta MS500 cavity drainage membrane over the inner faces of the retaining walls, all over a secret sub slab Delta pumped drainage system involving mid floor gulleys at regular spacings, linked with a Delta Dual V3 sump and pump system with high water alarm and battery backup.

Internal in situ concrete walls cast upon reinforced concrete kickers are protecting from rising damp internally by use of Delta Koster NB1 Grey crystalline slurry, applied within the joint and lapped down beneath the Delta MS20 cavity drainage DPM, which is sealed to the faces of the concrete internal walls using Delta Bitumen Primer in conjunction with Delta corner strip wide profile butyl tape to provide an adhesive key.

Case Study Results

Caddick Construction and Hugh Broughton Architects were delighted with Delta Membrane System Limited’s services, their onsite attendance, assistance and knowledge. Specifications were achieved efficiently and in a timely fashion which exceeded the expectations of all involved. Great work by our Registered installers Preserva CSS.

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