The Grove Hotel

BauderTHERMOFOL PVC single ply waterproofing system with an extensive green roof finish


The Grove Hotel is set in the Hertfordshire countryside. The private resort is a luxury five-star retreat with an award-winning spa, championship golf course and features unique restaurants and bars. The original first house of the building was founded in the 1500s. In 1996 the building was in a ruinous state and was renovated with the help of famous architects, interior designers and landscape gardeners. Seven years later in 2003, the luxury country house estate was opened as a hotel and spa.
However, in 2022 there was major water ingress from the roof of the Amber Suite, which needed rectifying. The client (Ralph Trustee) required a new waterproofing system that would last for more than 20 years. They also needed the roof finishes to complement the surrounding vegetated areas, as the balconies of the luxury hotel rooms overlooked the roof. The specification and installation of this project was contractor led by Delomac Roofing.

Bauder Building Board

Project: The Grove Hotel
Location: Hertfordshire
Project type: Refurbishment
Roof size: 645m2
Approved contractor: Delomac Roofing

The specification

The roof specification required replacing the roof with Bauder’s high quality waterproofing, plus a green roof finish to match the existing ground aesthetics.

The roof replacement of the original ballast involved overlaying with 645m2 of the BauderTHERMOFOL PVC waterproofing system. The overlay comprised of a separation fleece, followed by BauderTHERMOFOL U 15 FR Anthracite which was mechanically fixed. At all the upstands, a new plywood backing was installed and adhered the BauderTHERMOFOL U 15 FR. The BauderPVC ABL-R 75 rigid PVC vertical outlets were dropped into the existing outlets and downpipes with a compression seal allowed sealing of the waterproofing membrane to a new outlet. This meant there were no internal works to the amber suite needed.

A green roof finish was specified for the Amber Suite. A Bauder green roof combines the finished planting scheme and all its supportive components with a secure waterproofing system. The chosen vegetation finish for the green roof were Plug Plants which are designed to be comparatively lightweight. The 'plugs' are varieties of sedums, grasses, herbs and perennials and are planted by hand to the required density. This is particularly useful for small green roofs where a high aesthetic finish is required. Bauder’s British Native Species plugs are all grown in the UK and sourced in line with the Flora Locale Code of Practice.

Products applied

BauderTHERMOFOL U 15 FR membrane
This single ply membrane is lightweight and has a high-grade virgin polymer formulation. The PVC formulation ensures it is resistant to chemicals and micro-organism attacks, making it well suited to receive a green roof.

Bauder Plug Plants
Plug planting enables the greatest degree of control for the green roof designer. Bauder supplies approximately 300 different species of British native wildflower plugs, enabling the exact species to be supplied for a particular location.

Project challenges

The Bauder flat roof system was installed by Delomac Roofing. The biggest challenge on The Grove Hotel roofing project was the removal of over 80 tonnes of ballast which the installing operatives carried out by hand. The installers utilised approximately 35% to 40% of the ballast within the scheme by planting on the roof and the low-level gutter. However, to minimise waste, the remaining product was used by The Grove Hotel elsewhere.

The installing operatives carried the works out in sections to minimise the amount of ballast that had to be moved from roof to ground level, which also meant they were able to focus on installing one section of the roof at a time. The gutter was completed first as this was where the ballast would be utilised. The next section completed was the main roof, because all the ballast could be moved into the gutter on completion and the excess was then removed to a designated area, agreed with the hotel.

As The Grove Hotel is a live hotel and events venue, this also raised some potential logistical challenges. To overcome these challenges, the contractor was provided a programme of events and dates during which different types of works were allowed, for instance, on days when events were taking place no noise was allowed to be made. Therefore, the installers planned their work to fit in with the schedule and to meet the expectations of the hotel. ​

Access to the roof was only made internally through a hotel bedroom. This was to stop any guests being able to access externally via a ladder. There were also clear demarcation routes signed below the works for the guests. Additionally, the site had limited access; only 7.5 tonne rigid vehicles were suitable for site deliveries and Delomac Roofing had no means to offload the vehicles. This meant all the materials had to be safely manually distributed to the hoist. To limit the distances materials had to be moved on the ground, a flatbed van was used on site to transport materials to and from areas.

The works to the lead piers and capping proved to be complex. These faceted details were removed and redressed in Thermofol membrane by Delomac’s skilled operatives which took time to carefully create the lead like faceted detail.

The result

Due to the integral pre-project planning by Delomac, Bauder and The Grove hotel, all works were met within the budget and on time. Bauder and the approved contractor worked closely together throughout the project. Throughout the project, there was a full-time SSSTS operative who ran the works daily on site. A Bauder site technician carried out interim inspections to ensure the quality was up to standard throughout the installation process. There was clear communication between operatives from Delomac, Bauder and The Grove Hotel Team in regard to health and saftey. A final roof inspection of the installation on completion of the project was carried out by the Bauder site techician, before final sign off and guarantee of the project.