Why Commercial Stairwells in the Western Cape Need Waterproofing

Commercial stairwells need waterproofing in the Western Cape because the region takes most of its rain in a few winter months, and a stairwell is a vertical channel where water enters through walls, joints and roof edges and then runs down. Left untreated, that water corrodes reinforcement, spoils finishes and leaves wet, slippery steps in your main escape route. A sound waterproofing and drainage system, checked on a schedule, is the cheapest way to prevent all of it.

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TL;DR

The Western Cape is generally South Africa’s wettest region, and most of its rain falls in winter, so stairwells are tested hard for several months each year.
Water enters stairwells through cracks, failed sealant, joints, windows and roof edges, and it can travel a long way inside walls before you see a stain.
Persistent moisture corrodes steel reinforcement, cracks concrete and creates slip hazards on steps and landings.
Slope, drainage, flashing and good joint detailing do most of the protective work. Inspect before winter and after heavy weather.
Do the work in the dry summer months and hire a contractor who can show licensing, experience and a written warranty.

Why a stairwell is more exposed than it looks
How water gets into a commercial stairwell
What water does to a stairwell
What good protection looks like
When to inspect and maintain
Signs your stairwell is already letting water in
Timing the work for the Cape climate
Our perspective
How to choose a contractor for stairwell waterproofing
Get your stairwell assessed
FAQ
Sources

Why a stairwell is more exposed than it looks

A stairwell is easy to ignore. It sits at the edge of the floor plan, often has an external wall, a window-wall or open sides, and it connects the roof to the ground. Anything that gets into the top of the structure has a natural path downwards.

In the Western Cape that matters more than in most of the country. The regional climate profile describes the province as generally the wettest part of South Africa, with most rain in winter. Estate guidelines for a Cape Peninsula development make the same point: most rain falls between June and September, while summer is generally dry. So a small defect can sit unnoticed through a dry summer and then show itself in the first serious cold front.

Exposed stairwells also take wind-driven rain sideways. Rain that hits a wall or a window-wall at an angle is pushed into hairline cracks and joints that would stay dry in a vertical downpour. That is why a stairwell can leak even when the roof above it is sound.

How water gets into a commercial stairwell

Building-envelope specialists describe a leak as needing three things: water, an opening and a force to move the water through it. The same article names gravity, capillary action, kinetic energy and differential air pressure as the forces. In a stairwell, all four can be at work in the same winter storm.

Walls, joints and windows

The usual entry points are cracks, joints, windowsills, parapets, copings, lintels, penetrations and wall cavities, according to the same moisture-intrusion article. A professional investigation of a concrete building by IIBEC found that through-wall cracks and failed sealant around a steel window-wall system contributed to water reaching the stairs. Sealant is a wearing item. When it hardens, shrinks or pulls away, the joint becomes a path.

Steps, landings and horizontal surfaces

Horizontal waterproofing is the weak link in many structures. Structural engineering guidance points to flashing at horizontal waterproofing systems, guardrails, windows and penetrations as common leakage points that need integrated detailing. In a stairwell, think of guardrail posts fixed through a landing, a door threshold, or the junction between a landing slab and a wall. Each one is a place where the membrane has to be cut, lapped or sealed.

The same guidance says that slope and drainage are critical, because standing water can wear out membranes early or seep through to the substrate. A landing that holds a puddle will eventually leak.

Puddle beside a guardrail post on landing

Water that travels before it shows

The most expensive mistake is fixing the stain rather than the source. A New Zealand case study of a leaking office building found water entering above the visible damage and tracking down inside cladding and framing cavities. It ended in mould, rotting framing, cracked wet slabs and repeated flooding marks on stairwell landings, as Aamsko’s case study describes it. The same write-up notes that water may travel considerable distances inside wall or floor cavities before it appears as a stain. Patching the damp patch on a landing can therefore miss the real defect two floors up.

What water does to a stairwell

Structure

Most commercial stairwells are reinforced concrete. When moisture reaches the steel inside, it corrodes. IIBEC explains that corrosion of embedded reinforcement can make concrete crack, delaminate and spall, and that the cracking then lets in more moisture and can cause interior leakage. A transport authority’s inspection manual lists carbonation and chloride ingress as mechanisms that can start reinforcement corrosion, followed by cracking, delamination and spalling. For coastal buildings in Cape Town, chloride from sea air is a reason to take this seriously.

Steel stairs, handrails and wooden supports are affected too. Trade coverage notes that unchecked water damage can disintegrate steel and rot wooden supports, which leads to costly structural repairs.

Finishes and indoor environment

Damp stairwells peel paint, lift floor finishes, stain ceilings and grow mould. Mould and musty air in a common area reflect directly on a managed property, and tenants and visitors notice it first in shared circulation space. Moisture that reaches electrical fittings, lighting or signage adds another cost.

Safety

A wet stair is a slip hazard, and in a commercial building the stairwell is also an escape route. Safety rules differ by country and none of the following is South African law, but they show how regulators treat the problem:

New Zealand’s building regulator says access routes must have adequate slip-resistant walking surfaces under all conditions of normal use, and it specifically covers stairs and wet-to-dry transition zones.
California’s workplace regulation requires that slippery conditions on a stairway be eliminated before the stairway is used to reach another level.

For a South African building, confirm your obligations as owner or employer with your safety consultant and your municipality. The practical lesson holds anywhere: a stairwell that stays wet is a stairwell that needs fixing, not mopping.

What good protection looks like

The aim is to keep water out and, where it gets in, give it a way out. Structural guidance summarises the envelope approach as the “four Ds”: deflection, drainage, drying and durability. Applied to a stairwell:

Measure	What it does	Where it applies
Deflection	Keeps rain off vulnerable surfaces	Copings, parapets, sills, window heads
Drainage	Moves water away fast	Sloped landings, roof outlets, gutters, weep holes
Flashing	Diverts water outward at junctions	Windows, guardrail posts, penetrations, wall-to-roof joints
Membrane or coating	Forms a continuous barrier	Landings, external stairs, roof slabs above the stairwell
Sealant	Closes movement joints and cracks	Façade joints, window frames

The moisture-intrusion article recommends sloped horizontal joints, flashing and weep holes to divert moisture outward, plus proper roof drainage, and notes that sealants need suitable selection and application. In other words, products matter less than detailing and workmanship. A good membrane over a poorly drained landing will still fail.

If the stairwell sits under or beside a roof deck, treat the two as one system. Our guide to commercial waterproofing in South Africa explains how roofs, decks and structural elements fit together. If your roof has a planted area, see rooftop garden waterproofing for commercial buildings.

When to inspect and maintain

Waterproofing is not fit-and-forget. Maintenance guidance from a membrane manufacturer’s guarantee documents calls for routine cleaning of outlets, inspection for physical damage, annual inspections in spring and late autumn, more frequent checks in high-risk locations, and an extra inspection after adverse weather or work by other trades. That guidance is British, so translate the seasons for the Cape: check before the winter rains arrive and again once the worst of them has passed.

A practical stairwell routine:

Before winter: clear outlets, gutters and weep holes, and look for cracked or shrunken sealant and hairline cracks in external walls.
After the first heavy storm: walk the stairwell from the top down and look for damp patches, efflorescence (white salt deposits), peeling paint and pooling on landings.
After other trades work nearby: cable, aerial, signage or façade work often punches holes through the waterproofing. Check those spots.
Record everything: dated photos make it easy to see whether a stain is growing.

Our waterproofing inspection checklist gives you a longer list to work from, and the maintenance guide for South African properties covers upkeep after the work is done. For the wider case, read why waterproofing systems need maintaining.

Signs your stairwell is already letting water in

You do not need a specialist to spot early warning signs. Look for:

Damp or dark patches on walls or ceilings, particularly below windows and at the top of the stairwell.
White crystalline deposits on concrete or plaster.
Bubbling, flaking or peeling paint and lifting floor coverings.
Rust staining or cracked, flaking concrete around handrail fixings and steel edges.
A musty smell, or visible mould in corners.
Puddles that remain on landings long after rain stops.

If you see any of these, do not stop at the stain. As the case study above shows, the entry point may be well away from the visible damage, so ask a contractor to trace the water to its source before choosing a repair.

Timing the work for the Cape climate

Because the rain is concentrated in winter, the best window for membrane and coating work is summer, when substrates can dry. Most waterproofing systems need a dry surface to bond properly, so booking in autumn or winter can mean waiting for a weather window. Planning in late spring gives you time to survey, get quotes and compare scope before the dry months, rather than scrambling when the first leak appears. Emergency fixes in the rain are sometimes necessary, but they are usually temporary.

Our perspective

Most stairwell leaks we hear about are not dramatic failures. They are small defects that went unchecked through a dry summer: a tired sealant joint, a blocked outlet, a landing that never drained properly.

Our view is that the biggest saving for a building owner comes from two things: finding the true source of the water, and hiring the right contractor to deal with it. That is why our site puts so much weight on the questions you should ask any contractor: about licensing, experience, a clear written scope and a warranty you can rely on.

A stairwell is a safety space as well as a structural element. We would rather you treat waterproofing as part of normal building care, planned before winter, than as an emergency in July.

Eben

How to choose a contractor for stairwell waterproofing

A stairwell job touches walls, joints, landings and often the roof, so the quality of the contractor matters as much as the product. Ask for:

Licensing and insurance: proof that the company is registered and covered for work at height on commercial property.
Relevant experience: similar commercial or industrial projects, not only houses.
A written scope: which surfaces, which system, how drainage and flashing details will be handled, and how existing cracks will be treated.
A source-first diagnosis: a plan that traces the water to its entry point rather than covering the stain.
A warranty: its length, what it covers and what maintenance it expects from you.

Our comparison of waterproofing contractors in South Africa and the complete waterproofing checklist for owners walk through the full process.

Get your stairwell assessed

If you manage or own a commercial or industrial building in the Western Cape, we connect you with vetted waterproofing professionals who can inspect stairwells, landings and the roof or walls feeding them, and quote for the right fix. Send us the details of your building through our waterproofing quote request and we will start the introduction.

It helps to have photos of any stains, the age of the building and the date of the last waterproofing work ready when you enquire.

FAQ

Do all commercial stairwells need waterproofing?

Any stairwell with an exterior wall, window-wall, exposed landing or roof above it can take in water, so most do in practice. In the Western Cape, where most rain arrives in winter, the exposure is concentrated and intense. A contractor can tell you which parts of your stairwell need a membrane, which need sealant, and which just need better drainage.

Why does water appear on a landing when the roof looks fine?

Water often enters higher up or at the side and travels through wall or floor cavities before it shows. Investigators have found that water can move a long way inside cavities before appearing as a stain. Window frames, sealant joints, parapets and guardrail fixings are the usual suspects, so the survey should cover those, not just the roof.

How often should a stairwell be inspected?

At least twice a year is a sensible baseline, matching manufacturer guidance of spring and late autumn inspections, adjusted to the Cape’s seasons. Add a check after severe storms or after other trades have worked on the building.

What happens if I ignore a damp stairwell?

Moisture can reach the reinforcement, which then corrodes, and corroding steel can crack and spall the concrete. Finishes deteriorate, mould can develop and wet steps become a slip risk. Repair costs generally grow the longer the cause is left.