by Dorothy Wallace, Live Easy & Ryan Kane, Structure Pros
On our islands, water is the operating environment. Salt-laden air, high humidity, wind-driven rain, and storm exposure don’t just affect finishes: they affect core underlying assemblies. Repainting something is maintenance. Waterproofing is a system performance.
Balcony Assemblies
Most elevated balconies are reinforced concrete slabs. Embedded inside that slab is reinforcing steel (rebar). Concrete protects that steel. But only as long as chlorides and moisture don’t penetrate it. In marine environments, salt migrates into porous concrete over time. Once moisture reaches reinforcing steel, corrosion begins. Rust expands, creating internal pressure that causes cracking and spalling (the flaking concrete often seen at slab edges). Once corrosion starts, surface coatings do not stop it; they merely hide the deterioration.
Proper balcony waterproofing typically includes:
• Crack repair and surface preparation
• A continuous fluid-applied or sheet membrane
• Reinforcing fabric at transitions
• Proper termination at thresholds
• Metal drip edges and flashing
• Positive slope
Cementitious “waterproof” coatings are often marketed as a simple solution for concrete and masonry surfaces. These products can resist moisture penetration under ideal conditions, but they rely entirely on substrate integrity. They do not accommodate structural movement well, and they are not substitutes for mechanical water barriers.
Screen Enclosures
Screen enclosures introduce dozens, sometimes hundreds, of slab penetrations. Each fastener interrupts the protective concrete cover over reinforcing steel. In salt-exposed environments, improperly coated fasteners corrode, expand, and crack the surrounding concrete, creating pathways for water intrusion. Best practice includes stainless steel fasteners, proper sealant at penetrations, and isolation detailing between aluminum framing and concrete. Water intrusion here is rarely dramatic: it is cumulative.
Stucco Over Frame
Many island homes are wood-frame construction with stucco cladding. Stucco is not waterproof. It is designed to shed water. Beneath it should be a continuous water-resistive barrier (WRB), properly lapped flashing, and integrated drainage detailing. When cracks develop, and they inevitably do, wind-driven rain can enter. If flashing or WRB installation is flawed, water reaches the sheathing and framing, concrete spalls, and the wood rots, and wood-boring organisms that rely on water are highly likely to prevail. Framing deterioration can remain hidden for years before visible symptoms appear. Applying elastomeric paint over cracked stucco does not correct failed flashing or improperly integrated barriers. Waterproofing framed construction is about layered defense from the inside out.
Josh Michalski of Crevalle Consulting provided the photo and explained why it is important to prevent water from reaching the framing. “The reason may seem obvious, but we see conditions like this all too often. At the top of the balcony, a gap between the concrete topping and the wood column allowed a substantial leak for years. The water caused extensive deterioration of the decking, beams, and columns, requiring significant structural repairs. Yes, waterproofing can be expensive. Yes, it can be intrusive to remove existing systems to install it properly. But deterioration like this is all too common and is significantly more expensive to repair than the initial waterproofing would have been. Preventative maintenance now prevents future repairs later.”
Real Systems vs. Surface Solutions
There is a difference between engineered waterproofing assemblies and consumer-grade rubberized coatings marketed as universal fixes. Consumer-grade coatings, like Flex Seal, may serve temporary, minor repair needs, but they are not engineered to prevent chloride intrusion, remediate reinforcing steel corrosion, or replace integrated flashing systems. Only engineered waterproofing systems can provide real protection.
On the islands, proper waterproofing is essential. Repairs can cost 10 times as much as a proper waterproofing system, and these costs can escalate quickly. Past storm events have already introduced moisture into vulnerable assemblies. Waterproofing the building envelope may well be the most under-scrutinized and poorly executed phase of construction, although the repairs and damage that appear later will certainly get your attention.