6 Sarnafil Roofs

These inner city apartments were built on the roof of an old warehouse building in the mid 1990s and the roof covered with Sonogard liquid applied polyurethane membrane.
No slope was built into the roof structure, in fact it was designed to actually hold water on the roof, with the use of 50mm high trangular timber battens 200mm in from the perimeter edges restricting the flow of rain water to the drains.
All very well if the membrane stays 100% watertight, but a disaster if there is a failure of the membrane.
In this case there was parial failure of the polyurethane coating at some of the plywood joints. Although quite a flexible product the pu could not cope with the expansion and contraction that the substrate was undergoing every day, and it is quite likely the layer of water did not help in this, in fact adding to the heat buildup in the Summer like a magnifying glass.
We were asked to have a look at re sloping the roofs and then apply either a Butynol rubber or a Torchon membrane. After much research into methods of re sloping such as timber framing (too heavy) and tapered insulation from Europe (too expensive) and then also taking into consideration the design restrictions of the height of those windows off the roof and they type of cladding on the opposite walls, this idea was abandoned.
The only product on the New Zealand market that would provide a Guarantee on their membrane under ponding conditions turned out to be Sika Sarnafil.
2mm thick Sika Sarnafil PVC G410-20 L Felt (fleecebacked) laid in Sarnacol contact adhesive. inspected by a Sika Rep on completion and Certifed by Sika Sinagpore this project obtained a 20 Year Guarantee.
The Sonogard membrane was thoroughly cleaned with a commercial degreaser and then rinsed off, the perimeter metal edge flashings were removed, with great difficulty I might add due to being bedded in silicone sealant, and then refixed again after application of the Sarnafil, the ring clamp drains were rescued and the wall cladding loosened off to allow an upstand at the walls then re-tightened. Those nasty triangular batten water checks were removed to allow water to flow to the drains ( as best it can).
At the big windows the membrane was dressed up under the aluminium window frames with a bead of Sikaflex polyurethane sealant along the underside edge, then covered with a Sarna Termination Bar, again bedded in Sikaflex on top of the Sarnafil membrane, screwed to the outside of the window frame and sealed a 3rd time along the top edge with Sikaflex.
The work was spread over 3 months of the 2010/2011 “Summer”, which was a windy one. The location is extremely exposed, at all times safety was paramount, not only for us workers, but for the public below in the street. With no storage facilities on site every piece of material and all tools and equipment had to come down off the roof every afternoon.
Here are some photos of the work. Clicking on individual photos will open a larger version in another tab ( or window in IE)
corner building roofs on the top floor access by scaffold at the rear six roofs four ladders to the end one one of the lower roofs typical higher roof failed sonogard pu drain and waterchecks watercheck along the wall another drain and waterchecks all the roofs pond water dan removing a watercheck dan sealing up the cut out typical recess where the watercheck was drain corner with watercheck removed another corner with watercheck out degreaser wash, south end roof opposite view north end roof is clean, and wet next day, starting to lay the sarnafil long way down adhesive tacking off 2nd sheet glued up 2nd sheet tacking off close up of adhesive on roof and sheet folding down the sheet other half of 2nd sheet gluing up the last sheet last sheet tacking off perimeter is temporarily sealed with butyl sealant clamp drain is re-used typical welded 80mm lap/seam dan screwing down the u bar around edge mike doing the same closeup of u bar fixed down feeding the 4mm pvc rod through the hot air gun pvc rod welded to the sheet (on the right) 1.5mm thick detail membrane strip glued up detail strip dressed over the watercheck metal edge flashing is reattached over view of outside edge metal lower (2nd) roof wash clean, but wet dan gluing up the 1st full width sheet part done laying 2nd roof mike hot air welding the seams lower roof feild sheets are down 1st and 2d roofs feild areas done lower (2nd) roof is flooded after rain lake detail strip flashing to vents, 1st roof another vent roofed in lower view of vent detail more rain overnight washing the 3rd roof in the rain lower (4th) roof being degreased 3rd roof being laid up in 2mm sarnafil 3rd roof done view over the first 3 roofs 5th (upper) roof laid and u bar down edge detail strip glued up detail strip in place and welded edge metal back on (roof 5) typical detail at window corner, lower roofs u bar under windows detail strip installed under window corner detail in sarnafil termination bar under windows typical upper and lower roof completed back to the 4th (lower) roof ready to lay laying the sarnafil, west end 4th roof laying the sarnafil, east end 4th roof 4th (lower) roof laid opposite view detail strip under window ready for welding welding done all done this side out at the edge, roof 6 cleaning up the watercheck, roof 6 u bar screws bedded in pu sealant here, due to threat of rain last detail strip going on, very windy last strip down and welded edge metal back on sharp corner we are done here

Advertisements