In heritage buildings, waterproofing is never simply a matter of applying a coating.
Every intervention must protect the building from water ingress while respecting its existing structure, architectural character and often-complex detailing. This becomes particularly important in roof drainage areas, where even a small defect can allow water to penetrate deeply into walls, ceilings and historic finishes.
Safeguard Chemicals recently supplied a polyurethane waterproofing system for the wooden box gutters of a cathedral in Cape Town.
Following the first significant weekend rainfall after completion, the client reported:
“We had zero leaks or evidence of moisture after this weekend’s rains. Safe to say the application was successful.”
That is the result every waterproofing project should ultimately be judged by.
Wooden box gutters are often hidden between roof slopes, parapets and adjoining walls. Unlike external gutters, a failure may not be immediately visible from ground level.
They are exposed to several demanding conditions:
On a heritage building, the consequences of failure can be especially serious. Water entering through a wooden box gutter may damage timber, ceilings, plaster, masonry, decorative finishes and other historically significant elements long before the source of the leak is correctly identified.
The objective must therefore be to create a continuous waterproofing system capable of accommodating the gutter’s geometry and normal movement while maintaining strong adhesion to the prepared substrate.
The cathedral’s wooden box gutters were protected using Safeguard PU 720 and PU 290 as a compatible polyurethane waterproofing system.
PU 720 was used as the preparatory primer to promote adhesion between the correctly prepared gutter substrate and the waterproofing coating.
A waterproofing system is only as reliable as its bond to the substrate. Correct preparation and priming are therefore critical, particularly where existing surfaces, junctions and previous repair areas are involved.
PU 290 formed the seamless waterproofing and protective layer over the prepared and primed box gutters.
Because it is liquid-applied, the coating can follow the shape of the gutter and be worked into junctions, upstands and other details where rigid or sheet materials may be difficult to install.
Once cured, it creates a continuous protective barrier without the multiple laps and seams commonly associated with sheet-based waterproofing.
PU 720 and PU 290 were specified and applied as one compatible system – not as unrelated individual coatings.
Heritage wooden box gutters frequently contain irregular dimensions, difficult transitions and interfaces between different construction materials.
A correctly specified liquid-applied polyurethane system offers several practical advantages:
The absence of an open-flame application method is particularly relevant when working around historic roof structures and potentially combustible building materials.
The rain provided the first real-world performance check
Visual inspection after application is important, but waterproofing ultimately has to perform under real exposure.
Cape Town’s rainfall provided the first meaningful site check. Following the weekend rains, the client confirmed that there were no leaks and no evidence of moisture ingress.
This successful outcome demonstrates what can be achieved when the substrate is properly assessed, the details are correctly prepared and a compatible primer and liquid-applied waterproofing coating are installed as a complete system.
It is an encouraging result – but responsible waterproofing does not end after the first rainfall. Heritage roof drainage systems should continue to be inspected and maintained, particularly before and during the winter rainfall season.
Outlets must remain clear; water must be allowed to discharge freely and any later work carried out by other trades must not puncture or damage the waterproofing system.
Heritage waterproofing begins with diagnosis
Historic buildings should never be subjected to a generic “coat and hope” repair.
Before selecting a system, the source and pathway of moisture must be established. This requires assessment of the gutter substrate, outlets, falls, joints, roof interfaces, parapets and previous repairs.
The most durable intervention is the one that addresses the actual route of water ingress while causing the least unnecessary disturbance to the building.
Before :
After:
At Safeguard Chemicals, our approach is simple:
Diagnose the cause. Design the system. Protect the building.
For this Cape Town cathedral, the first rain brought very welcome confirmation: the restored wooden box gutters performed successfully, with zero leaks and no evidence of moisture ingress.
A quiet result, perhaps – but for a heritage building, an extremely important one.
Safeguard Chemicals SA
Waterproofing and damp-proofing systems supported by technical diagnosis, specification guidance and application training.
🌐 www.safeguardchem.co.za
✉️ technical@safeguardchem.co.za
#HeritageBuildings #HeritageWaterproofing #Waterproofing #BoxGutters #PolyurethaneWaterproofing #BuildingConservation #CapeTownArchitecture #RoofWaterproofing #MoistureManagement #SafeguardChemicals
Waterproofing of roofs, basements, etc. shall be laid under appropriate manufacturer guarantees supplemented
by a contractor workmanship guarantee. Waterproofing to flat roofs shall be laid with a minimum fall to outlets of
1:80 and include all outlets, etc.Waterproof of external basment walls shall take into account the definition of dry and wet sides as per SANS 10021: 2006 6.15.2 and 6.1.5.3 and provide one or two layer membrane systems as
appropriate descriptions of sheets or membrane waterproofing shall be deemed to include all labour costs.
Apply Safeguard SG720″ primer to prepared surfaces, followed by two coats of “Safeguard SG280” waterproofing polyurethane and one coat of SG PU440 with SG PU Fabric on horizontal and vertical joints.
Apply Safeguard SG720″ primer to prepared surfaces, followed by two coats of “Safeguard SG280” waterproofing polyurethane and one coat of SG PU450 with SG PU Fabric on horizontal and vertical joints.
Thoroughly clean and prepare the surface, as per Safeguard Method Statement for Surface Preparation.
Apply one coat of Safeguard solvent-based Bitumen Primer to the surface ensuring full coverage without any “ponding” of primer on the surface.
Allow to dry and heat-fuse one layer of Safeguard Euro Gecko 4mm APP single re-inforced Bitumen Membrane to the primed surface, lapping all side walls and dressing into and around outlets and upstands.
Provide 100mm side laps and 150mm end laps to adjoining rolls of membrane, ensuring that laps are properly “bled”.
Suitable performance-related products are acceptable.
5-7 days after application of the Bitumen Membrane, thoroughly clean the surface of the membrane and apply 2 coats of Safeguard Bitumen Aluminium paint to the membrane using a brush, roller or spray.
Equivalent products are acceptable.
Thoroughly clean and prepare the surface, removing all laitance, dust, dirt, grime and grease.
Apply one coat of solvent-based Bitumen Primer to the surface ensuring full coverage without any “ponding” of primer on the surface.
Allow to dry and heat-fuse one layer of 4mm APP single re-inforced Bitumen Membrane to the primed surface, lapping all side walls and dressing into and around outlets and upstands.
Provide 100mm side laps and 150mm end laps to adjoining rolls of membrane, ensuring that laps are properly “bled”.
5-7 days after application of the Bitumen Membrane, thoroughly clean the surface of the membrane and apply 2 coats of Bitumen Aluminium paint to the membrane using a brush, roller or spray
Thoroughly clean and prepare all external walls from foundation to 2 brick courses above finished ground level as per Safeguard Method Statement for Surface Preparation.
Apply one coat of Safeguard SG 720 Primer to the walls by spray, roller or brush and allow to dry.
Apply two coats of Safeguard SG PU 610 by spray, roller or brush. If applying by spray, dilute with 5% MEK. Allow the first coat to dry overnight. A third coat should be applied where “Wet” sites are encountered as per SANS 10021:2006 6.1.5.3
Protect membrane with soft board or dimpled membrane prior to backfill.
Equivalent performance-related products may be supplied.
Thoroughly clean and prepare all external walls from foundation to 2 brick courses above finished ground level, removing all dirt, dust, grime grease and any unnecessary mortar,
Apply one coat of Polyurethane Primer to the walls and allow to dry.
Apply two coats of Polyurethane waterproofing membrane to a DFT of 1-2mm. The membrane should accommodate temperatures from -30? to +90?C and have a minimum elasticity of 600% with a Shore A hardness of 60 or greater and a Tensile strength of 4N/mm? or greater. Allow the first coat to dry overnight. A third coat should be applied where “Wet” sites are encountered as per SANS 10021:2006 6.1.5.3
Protect membrane with soft board or dimpled membrane prior to backfill.
Thoroughly clean shower walls and floor, removing all loose dirt, mortar, grime and grease. Walls should not be plastered.
Apply a coat of Safeguard Latseal Slurry mixed with Bondaid to the walls and floor, embedding a non-woven polypropylene membrane into the slurry at all joints.
Allow to cure overnight and apply a further coat of Safeguard slurry to the entire area.
At the joint with the outlet, an expandable polyurethane sealant should be applied to cover both surfaces. This should be allowed to cure, together with the slurry before application of any tiles/mosaics.
Equivalent products are acceptable.
Thoroughly clean shower walls and floor, removing all loose dirt, mortar, grime and grease. Walls should not be plastered.
Apply a coat of cementitious waterproof slurry mixed with bonding liquid to the walls and floor, embedding a non-woven polypropylene membrane into the slurry at all joints.
Allow to cure overnight and apply a further coat of slurry to the entire area.
At the joint with the outlet, an expandable polyurethane sealant should be applied to cover both surfaces. This should be allowed to cure, together with the slurry before application of any tiles/mosaics.
PRODUCT GUARANTEE
Polyurethane Roofing – SG PU280
Polyurethane Foundation – SG PU610
Joint Sealant – SG Flex20
Bitumen Roofing – 4mm Torch-on membrane
Polyurethane Undertile Showers / Balconies – SG PU610
Cementitious Undertile Showers/Balconies – Latseal Slurry
SG PU 280 Flat Roof
SG PU 610 Garden Roof
SG 4mm Bitumen Roof
SG PU 610 Foundation
SG PU 280 Car parking
Waterproofing of roofs, basements, etc. shall be laid under appropriate manufacturer guarantees supplemented
by a contractor workmanship guarantee. Waterproofing to flat roofs shall be laid with a minimum fall to outlets of
1:80 and include all outlets, etc.Waterproof of external basment walls shall take into account the definition of dry and wet sides as per SANS 10021: 2006 6.15.2 and 6.1.5.3 and provide one or two layer membrane systems as
appropriate descriptions of sheets or membrane waterproofing shall be deemed to include all labour costs.
Apply Safeguard SG720″ primer to prepared surfaces, followed by two coats of “Safeguard SG280” waterproofing
polyurethane and one coat of SG PU440 with SG PU Fabric on horizontal and vertical joints.
Apply Safeguard SG720″ primer to prepared surfaces, followed by two coats of “Safeguard SG280” waterproofing
polyurethane and one coat of SG PU450 with SG PU Fabric on horizontal and vertical joints.
Thoroughly clean and prepare all external walls from foundation to 2 brick courses above finished ground level as per Safeguard Method Statement for Surface Preparation.
Apply one coat of Safeguard SG 720 Primer to the walls by spray, roller or brush and allow to dry.
Apply two coats of Safeguard SG PU 610 by spray, roller or brush. If applying by spray, dilute with 5% MEK. Allow the first coat to dry overnight. A third coat should be applied where “Wet” sites are encountered as per SANS 10021:2006 6.1.5.3
Protect membrane with soft board or dimpled membrane prior to backfill.
Equivalent performance-related products may be supplied.
Thoroughly clean and prepare all external walls from foundation to 2 brick courses above finished ground level, removing all dirt, dust, grime grease and any unnecessary mortar,
Apply one coat of Polyurethane Primer to the walls and allow to dry.
Apply two coats of Polyurethane waterproofing membrane to a DFT of 1-2mm. The membrane should accommodate temperatures from -30? to +90?C and have a minimum elasticity of 600% with a Shore A hardness of 60 or greater and a Tensile strength of 4N/mm? or greater. Allow the first coat to dry overnight. A third coat should be applied where “Wet” sites are encountered as per SANS 10021:2006 6.1.5.3
Protect membrane with soft board or dimpled membrane prior to backfill.
Thoroughly clean and prepare the surface, as per Safeguard Method Statement for Surface Preparation.
Apply one coat of Safeguard solvent-based Bitumen Primer to the surface ensuring full coverage without any “ponding” of primer on the surface.
Allow to dry and heat-fuse one layer of Safeguard Euro Gecko 4mm APP single re-inforced Bitumen Membrane to the primed surface, lapping all side walls and dressing into and around outlets and upstands.
Provide 100mm side laps and 150mm end laps to adjoining rolls of membrane, ensuring that laps are properly “bled”.
Suitable performance-related products are acceptable.
5-7 days after application of the Bitumen Membrane, thoroughly clean the surface of the membrane and apply 2 coats of Safeguard Bitumen Aluminium paint to the membrane using a brush, roller or spray.
Equivalent products are acceptable.
Thoroughly clean and prepare the surface, removing all laitance, dust, dirt, grime and grease.
Apply one coat of solvent-based Bitumen Primer to the surface ensuring full coverage without any “ponding” of primer on the surface.
Allow to dry and heat-fuse one layer of 4mm APP single re-inforced Bitumen Membrane to the primed surface, lapping all side walls and dressing into and around outlets and upstands.
Provide 100mm side laps and 150mm end laps to adjoining rolls of membrane, ensuring that laps are properly “bled”.
5-7 days after application of the Bitumen Membrane, thoroughly clean the surface of the membrane and apply 2 coats of Bitumen Aluminium paint to the membrane using a brush, roller or spray.
Thoroughly clean shower walls and floor, removing all loose dirt, mortar, grime and grease. Walls should not be plastered.
Apply a coat of Safeguard Latseal Slurry mixed with Bondaid to the walls and floor, embedding a non-woven polypropylene membrane into the slurry at all joints.
Allow to cure overnight and apply a further coat of Safeguard slurry to the entire area.
At the joint with the outlet, an expandable polyurethane sealant should be applied to cover both surfaces. This should be allowed to cure, together with the slurry before application of any tiles/mosaics.
Equivalent products are acceptable.
Thoroughly clean shower walls and floor, removing all loose dirt, mortar, grime and grease. Walls should not be plastered.
Apply a coat of cementitious waterproof slurry mixed with bonding liquid to the walls and floor, embedding a non-woven polypropylene membrane into the slurry at all joints.
Allow to cure overnight and apply a further coat of slurry to the entire area.
At the joint with the outlet, an expandable polyurethane sealant should be applied to cover both surfaces. This should be allowed to cure, together with the slurry before application of any tiles/mosaics.
