Case Study · Single Ply Membrane Overlay
Single Ply Overlay Refurbishment at The Trinity Centre
A weathered flat roof at Cambridge Science Park, restored to full
watertightness with an adhered single ply overlay — renewing
waterproofing performance while working with the retained roof build-up,
avoiding the disruption of a full strip-out.
Renewing Performance Without a Full Strip-Out
Cambridge Roofers were appointed by Princebuild Limited to refurbish the
main flat roof at The Trinity Centre, Cambridge Science Park, Milton. The
existing roof covering had weathered over time, with visible surface
contamination, moss and debris build-up, and redundant flashing fragments
left over from previous repairs.
Rather than a full strip-out, the brief called for an adhered single ply
overlay system — providing renewed waterproofing performance while
working with the retained existing roof build-up.
What an Overlay Demands of the Substrate
Overlay systems place particular demands on the existing roof covering,
since the retained substrate has to be sound, stable and properly bonded
before a new membrane can be adhered over it.
Sound & Stable Base
The retained roof covering had to be inspected and confirmed sound,
stable and properly bonded before any new membrane could be adhered
over it.
Clearing Debris & Contamination
The roof needed to be thoroughly cleared of loose debris, vegetation
and surface contamination before preparation work could begin.
Localised Unstable Areas
Areas of loose, blistered or unstable material had to be identified
and made safe individually before the overlay could proceed.
A Large, Open Roof
Working across a large, fully open roof area meant careful sequencing
of the membrane laying and welding to maintain a weathertight surface
throughout the works.
Method & Sequence
Work began with a full inspection and preparation of the existing roof,
before the new membrane was adhered, welded and detailed across the
whole roof area.
Inspection & Preparation
The existing roof was cleared of loose debris, moss and redundant
material, and checked that the retained covering was adequately
bonded and dry enough to receive the new system.
Making Safe & Adhesion Trials
Localised areas of loose or unstable material were cut out and made
safe, and adhesion trials were carried out to confirm compatibility
between the existing roof and the proposed Sika adhesive.
Membrane Installation
Sikaplan SGK-18 fleece-backed PVC single ply membrane was adhered
across the main roof area using SikaRoof Adhesive-500, with all side
laps hot-air welded to form a continuous, fully bonded waterproofing
layer.
Detailing & Leak Detection Test
Perimeters, upstands, rooflight kerbs and penetrations were detailed
with compatible Sikaplan detailing membrane, pre-formed corners and
coverstrips, with termination bars and counter flashings securing all
exposed edges. On completion, an electronic leak detection test
verified the integrity of the new membrane before handover.
A Fully Welded, Warranted System
Sikaplan SGK-18 Single Ply Membrane
Perimeters, upstands, rooflight kerbs and penetrations were detailed
using compatible Sikaplan detailing membrane, pre-formed corners and
coverstrips, with Sika termination bars and counter flashings installed
to secure and weather all exposed edges.
From Weathered Roof to Welded Membrane
Existing Roof Condition
An aerial survey and close-up inspection showed visible surface
staining, moss, and debris and redundant flashing fragments across
the existing roof covering.
The aerial survey shows the condition of the existing roof before works began, with visible surface staining and debris across the covering.
Close-up of moss and surface contamination on the existing roof covering.
Redundant flashing fragments and debris cleared from the existing roof during preparation.
Perimeter Detailing
Termination bars and coverstrips were installed at the roof perimeter
to secure and weather the edges of the new membrane.
New single ply membrane installed with termination bar detailing at the roof perimeter.
Close-up of termination bar and coverstrip detailing along the roof edge.
Completed Roof
The finished roof provides a continuous, fully welded single ply
membrane across the whole roof area, restoring watertightness with a
back-to-back Sika manufacturer warranty.
Completed Sika SGK single ply membrane roof at The Trinity Centre.
Wide view of the completed single ply overlay roof at The Trinity Centre.
Watertight Again, Without a Strip-Out
The refurbishment at The Trinity Centre delivered a fully welded,
watertight single ply overlay system across the main roof area for
Princebuild Limited, restoring the performance of the roof without the
disruption of a full strip-out. The completed installation was verified
with an electronic leak detection test and is backed by a Sika
manufacturer warranty for the new waterproofing system.
Overlay, Not Strip-Out
Renewed waterproofing performance while retaining the existing roof build-up.
Fully Welded Membrane
Sikaplan SGK-18 laid and hot-air welded for a continuous, bonded finish.
Tested & Warranted
Verified by electronic leak detection and backed by a Sika manufacturer warranty.
Talk to Us About Single Ply Membrane Roofing
Whether it’s a full re-roof or an adhered overlay that avoids a
strip-out, our Sika-approved team can assess your existing roof and
recommend the most cost-effective, warranted solution.