Every multi-pour concrete structure has them: the lines where one pour ends and the next begins. Construction joints are unavoidable in slabs, columns, walls and foundations, since concrete simply cannot all be poured at once on any project of scale. What’s avoidable, though, is water finding its way through the gap between those sections once the building is complete. That’s precisely what construction joint sealing is designed to prevent, and it’s a detail that developers and commercial property owners can’t afford to overlook.
Why Construction Joints Are a Weak Point
A construction joint forms wherever a concrete pour is interrupted, whether that’s between floor levels, across a long slab poured in sections, or where a wall meets a footing. The two sections bond, but never quite as seamlessly as a single continuous pour would. That interface becomes a natural path of least resistance for water, particularly under hydrostatic pressure below ground, or wherever a joint sits exposed to rain and runoff above ground.
Left unsealed or poorly detailed, water travels through this gap and can carry on into the structure itself, reaching reinforcing steel, undermining slabs, or tracking into occupied space below. On commercial and industrial builds, where slabs and structural elements are inherently large, the number of construction joints across a single project can add up quickly, which makes getting the sealing detail right at every one of them a genuine priority rather than an afterthought.
How TT Waterproofing Approaches Construction Joint Sealing
Since 2014, TT Waterproofing has sealed movement joints, construction joints and perimeter gaps across Pretoria, Centurion and Midrand, and the same core principle applies to every joint we treat: use the correct system for that specific joint, not a generic fix that happens to be on the van.
Assessment first. We start by identifying exactly where a structure’s construction joints sit and what conditions they’re exposed to. A joint below a basement slab facing constant ground water pressure needs a very different approach to one running across an exposed rooftop parking deck.
Correct sealant selection. Where separate concrete pours or building sections join, we seal the joint with a system matched to its exposure and movement characteristics, whether that means a flexible polyurethane sealant, a hybrid MS polymer, or a waterstop detail built in ahead of the pour itself. The goal in every case is the same: water cannot travel through the gap between the two elements.
Proper preparation. Before any sealant goes in, the joint faces are cleaned and primed, and a backing rod is fitted where needed to set the correct sealant depth. This step is easy to rush and just as easy to get wrong, and it’s often the difference between a seal that lasts and one that fails within a season.
Application built to move with the structure. Concrete structures shift slightly with temperature, load and settlement over their lifespan. A sealant that can’t accommodate that movement will crack and separate again, which is why we use flexible systems that flex and compress as the building does, rather than rigid fillers that simply fight the movement until they fail.
Why This Matters More on Commercial and Developer Projects
For a developer or commercial property owner, a failed construction joint rarely stays a small problem. Water tracking through a slab joint below ground can compromise waterproofing across an entire basement level. A leaking joint on a parking deck or roof slab can affect the space below it long before the source becomes obvious. And on a project with dozens of joints across multiple pours, one poorly detailed joint is often all it takes to undermine the durability of the whole structure.
This is exactly why TT Waterproofing treats joint sealing as a specialist detail rather than a finishing touch. Every joint we seal, whether it’s a single construction joint on a small extension or dozens across a full commercial development, is backed by our 10-year workmanship guarantee, so property owners and developers have real assurance the detail was done properly the first time. It’s this level of care, applied consistently across every project, that has made our team trusted waterproofing specialists for homeowners, bodies corporate, developers and commercial property owners right across Pretoria, Centurion, Midrand and the wider Gauteng region.
Frequently Asked Questions
When should construction joints be sealed, during the build or afterwards? Ideally, joint detailing is planned before or during construction, since waterstops and correct joint preparation are far easier to install at that stage. Existing joints on completed structures can still be resealed effectively, though the approach depends on access and exposure.
How long does a properly sealed construction joint last? With the correct sealant system and preparation, a construction joint seal is built to last for years under normal movement and exposure. That’s why every joint we seal carries our 10-year workmanship guarantee.
Can construction joints be sealed on an occupied or operating building? Yes, in most cases. We assess access and exposure on site and plan the work to minimise disruption, which is particularly relevant on commercial and industrial sites that need to keep operating during the job.
Managing a development or commercial property with construction joints that need attention? Contact TT Waterproofing for a free, no-obligation on-site assessment and an itemised quote for the work.
