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Case Study

A partial roof replacement on the historic English Heritage building, 49 Kew Green.

49 Kew Green, Kew Gardens, London

Dating back from the early 18th to early 19th century, this grade II English Heritage building was home to the botanist Sir William Hooker.

49 Kew Green, also known as Methold House, is a historic building located in Kew, London. This Grade II listed building has significant historical value. It was the residence of Sir William Hooker (1785-1865), the first official Director of Kew Gardens. Hooker's legacy continued through his son, Sir Joseph Dalton Hooker (1817–1911), who also became a distinguished botanist and succeeded him as Director of Kew Gardens. Ever since, the house has been the home of every Kew Gardens Director during their time in office. The house is situated on Kew Green, a large open space in west London, known for its picturesque surroundings and proximity to the Royal Botanic Gardens. The building itself dates back to the early 18th century and features a distinctive brown brick façade with irregular two and three-story sections.

View products used in project

Location

49 Kew Green, Kew Gardens

Requirements

The client required a solution that would ensure that the longevity of the building would not be compromised. Retaining the original aesthetics of this historic English Heritage building was essential.

Why Permavent was chosen:

A section of the building’s low pitch roof (approximately 46m2) required replacing. Tudor handmade tiles, which were specified by English Heritage; are designed for a minimum pitch of 40°. The section of roof to be replaced was 31°. Permavent Plain Easy, which is made in Britain and can be used on roofs with a pitch as low as 17.5° was specified and installed due to the systems suitability with traditional tiling methods, maintaining the critical aesthetics of the roof. The system guarantees the waterproofing integrity of roof, which the traditional Tudor handmade tiles could not provide at the lower pitch.

Plain Easy was installed alongside the high-performance roofing underlay Permavent DRY+, a vapour permeable membrane which contributes to condensation control, provides optimum permeability, and is specifically designed for low pitched roof applications.

Permavent’s unrivalled 40 year product guarantee for Easy Roof in conjunction with Permavent Dry + and Permatac Butyl tape was the only solution to futureproof the life of the is wonderful historical building.

 

 

How Permavent was installed:

Philip Wells, Conservation Architect at Martyn Ashley Architects and an expert in the conservation design of historic buildings, specified Plain Easy from our award-winning Easy Roof System range.

Plain Easy is an innovative low pitched roofing solution that protects the roof by preventing water ingress into the batten cavity and allows tiles to be installed on any roof with a pitch as low as 17.5°.

This particular part of the historic building’s roof has a standard four hip design with a fascia board on one side and a valley gutter on the other three sides of the 31° pitched roof.

The installation on the fascia side was standard, however the three valley gutter sides proved more problematic.

A Nicholson Airtrak LB20 lay board ventilator was installed on the three gutter sections. However, this complicated the installation of the Plain Easy system, so Grace Ice and Water Shield was placed over the Nicholson ventilator, covered with code 05 lead, allowing the roofer to nail through Permavent DRY+ vapour-permeable membrane, and then installed over the AirTrak.

Butyl tape was also used to run down the rafters ensuring an airtight and waterproof seal around nail penetrations.

Plain Easy and Tudor handmade tiles were installed onto the low pitched roof.

Easy Roof System offered significant improvements to the historic roof whilst minimising any aesthetic changes to the profile or external appearance.

 

 

“The longevity of the roof at 49 Kew Green was of upmost importance, whilst also keeping the original aesthetics of the historic building’s roof in place. Permavent offered superior product that would guarantee that longevity by means of the Easy Roof System 40 Year Guarantee.
Plain Easy provided the ultimate solution for the low pitch roof angle with Tudor slate ensuring the aesthetics of the original roof features remained the same as when the building was originally completed. Permavent also provided excellent technical support.”
Danny Harkin, D.Harkin Roofing & Company Ltd.

Client:

English Heritage

Contractor:

D Harkin & Co (Roofing) Ltd
58 Beragh Hill Road
Ballyarnett
Londonderry
Derry
BT48 8LY

Roofing Contractors | L’ Derry | D Harkin & Co Roofing Ltd

Products used:

Plain Easy

Low pitch system for plain tiles

  • Pitch as low as 17.5°
  • Creates new areas for plain tile application
  • Extends the life of the roof by keeping battens dry
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Permavent DRY+

High Performance Membrane

  • High performance construction membranes
  • Vapour permeable
  • Integrated tapes, suitable in all UK wind zones
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Permatac Butyl Waterproof Sealant Tape

High Tack airtight sealing tape

  • High Tack
  • Airtight
  • Strong & flexible
 MORE
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