Restoring an ageing 2,500 m² torch-on roof.

This was a large refurbishment of an existing torch-on roof covering approximately 2,500 m². The aim was to retain serviceable parts of the roof while rebuilding the areas that could compromise the new waterproofing system.

The roof needed more than an overlay.

Parts of the plywood and OSB deck had deteriorated and required selective replacement. Existing outlets were renewed, additional ventilation shafts were introduced and local falls were reshaped so that water moved toward the drainage points instead of remaining on the field area.

Those works were completed before the main two-layer membrane build-up. This kept the waterproofing sequence tied to the real condition and geometry of the roof rather than treating the old surface as a uniform substrate.

The complete Börner waterproofing route.

The field build-up used GEBÖRTOL V Rapid primer, MONOPLEX SBS PV 180 S4 underlay and POLY-ELAST PV 180 S4 cap sheet. TEK Bitumen Wedges were used at selected uninsulated changes of direction so the membranes were not forced through a sharp internal corner.

How the refurbishment was sequenced.

1. 01
   Survey and repair mapping

   The existing torch-on surface, deck condition, drainage points and vulnerable details were reviewed before the refurbishment zones were defined.

2. 02
   Selective deck replacement

   Failed plywood and OSB sections were opened up and replaced to provide a sound base beneath the retained and renewed roof areas.

3. 03
   Drainage and falls correction

   Outlets were replaced and local roof falls were reformed to improve the flow of water toward the drainage points.

4. 04
   Ventilation and angle detailing

   Additional ventilation shafts were incorporated and weathered into the system. Selected uninsulated upstand junctions received bituminous angle fillets before the membranes were dressed through the change in direction.

5. 05
   GEBÖRTOL V Rapid + MONOPLEX SBS PV 180 S4

   Compatible prepared surfaces received the bituminous primer before the reinforced SBS underlay was installed as the first waterproofing layer.

6. 06
   POLY-ELAST PV 180 S4

   The mineral-finished cap sheet completed the two-layer waterproofing system across the field, laps, outlets, penetrations and perimeter details.

The completed roof.

The project delivered a renewed two-layer waterproofing surface across approximately 2,500 m² while addressing the defects beneath it. The repaired deck provided a sound base, the reworked falls improved drainage and the replacement outlets and added ventilation shafts were integrated into the new membrane system.

The successful part of this refurbishment was not simply the new cap sheet.
It was correcting the deck, drainage and details before the roof was closed again.