Insufficient Waterproofing Upstand and Termination Height – A Common Cause of Leakage
Technical guidance for architects, engineers, specification consultants and project teams
A waterproofing system may perform perfectly across a horizontal roof, balcony or podium deck, yet the building can still experience serious leakage if the waterproofing is terminated too low or incorrectly detailed.
This is one of the most frequently overlooked areas in waterproofing design.
Water does not remain only on the horizontal surface. During heavy rain, ponding, blocked drainage or wind-driven rain, water can rise against walls, parapets, door thresholds, equipment bases and other vertical interfaces.
If the waterproofing upstand is insufficient, water may simply travel above or behind the waterproofing system.
At Topkrete, we consider waterproofing termination an integral part of the waterproofing design.Waterproofing does not end where the horizontal surface ends.
What Is a Waterproofing Upstand?
A waterproofing upstand is the continuation of the waterproofing system from the horizontal surface onto a vertical surface.
Common locations include:
- Roof parapets
- Balcony walls
- Podium walls
- Planter boxes
- Door thresholds
- Equipment plinths
- Plant rooms
- Toilets and bathrooms
- Swimming pools
- Water features
- External walls adjoining decks
- Roof penetrations
The purpose of the upstand is to maintain continuity of the waterproofing system above the level where water may accumulate or splash.
However, simply turning the membrane vertically is not enough.
The height, termination method, substrate condition and protection of the upstand all need to be considered.
Why Is Upstand Height Important?
Consider a flat roof during normal conditions.
Rainwater falls onto the roof and flows towards the outlet.
If drainage is functioning properly, the water level remains relatively low.
But what happens when:
- The outlet becomes partially blocked?
- Heavy rainfall exceeds the immediate drainage capacity?
- Leaves or debris obstruct the drainage point?
- The screed does not have sufficient falls?
- Water ponds around an equipment base?
- Wind pushes water against a parapet or doorway?
The water level may temporarily rise.
If the waterproofing upstand terminates below that level, water can enter behind the membrane.
Once water reaches the substrate behind the waterproofing, the membrane itself may no longer be able to prevent leakage.
Consultant Consideration
The waterproofing termination height should therefore be determined based on anticipated water exposure and project detailing, not simply convenience during installation.
1. Roof Parapets
Roof parapets are one of the most important areas requiring proper waterproofing upstands.
A common arrangement is:
Roof slab → screed to falls → waterproofing membrane → parapet upstand → termination/protection.
The waterproofing should continue sufficiently up the parapet to protect against:
- Ponding water
- Wind-driven rain
- Splashing
- Drain blockage
- Water accumulation at the roof edge
The upper edge of the waterproofing must also be properly terminated.
Otherwise, water running down the wall may travel behind the membrane.
Depending on the selected waterproofing system, termination may involve:
- Recessed termination
- Termination bar
- Counter flashing
- Metal flashing
- Compatible sealant
- Protective render
- Mechanical fixing
Important Principle
A high upstand with a poor termination can still leak.
Upstand height and termination should always be designed together.
2. Door Thresholds and Balcony Entrances
Door thresholds present a particularly challenging waterproofing detail.
Architectural requirements increasingly favour:
- Flush thresholds
- Minimal steps
- Level access
- Large sliding doors
However, external balconies and terraces remain exposed to rain.
If the external finished floor level is too close to the internal floor level, water may enter through the doorway during:
- Heavy rainfall
- Blocked drainage
- Ponding
- Wind-driven rain
Consultants therefore need to coordinate:
Door level + waterproofing upstand + external floor level + internal floor level + drainage.
Where a high waterproofing upstand is not possible because of architectural requirements, additional design measures may be necessary.
These may include:
- Linear drainage channels
- Secondary drainage
- Recessed balcony levels
- Carefully detailed door frames
- Waterproofing beneath the threshold
- Appropriate membrane termination
Consultant Consideration
A flush architectural detail should never be achieved by simply reducing waterproofing protection without considering the increased water-ingress risk.
3. Plant Rooms
Plant rooms frequently contain water sources and drainage systems.
Possible sources of water include:
- Equipment leakage
- Condensation
- Pipe failure
- Cleaning
- Maintenance activities
- Drainage blockage
Waterproofing should therefore generally extend vertically at perimeter walls, kerbs and equipment bases according to the expected exposure.
Particular attention should be given to:
- Doorways
- Pipe penetrations
- Floor drains
- Equipment bases
- Wall-to-floor junctions
If a plant-room floor is waterproofed but the membrane stops exactly at the wall-floor junction, water may enter the adjoining wall or room.
4. Toilets, Bathrooms and Wet Areas
Wet-area waterproofing is another application where vertical continuity is important.
Water exposure occurs not only on the floor but also around:
- Shower areas
- Wall-floor junctions
- Pipe penetrations
- Sanitary fittings
- Floor traps
- Doorways
Consultants should clearly identify which walls require waterproofing and to what height.
The design should consider the actual wet zone rather than treating all areas identically.
For example, a shower wall is subject to significantly greater direct water exposure than a wall outside the shower zone.
Consultant Consideration
Waterproofing heights should correspond to the actual exposure condition of each area.
5. Planter Boxes
Planter boxes are particularly demanding waterproofing applications because water may remain within the planter for extended periods.
The waterproofing system should be continuous across:
- Planter base
- Internal walls
- Corners
- Drainage outlets
- Pipe penetrations
The membrane should also terminate at a suitable level above the expected soil and water zone.
Other considerations include:
- Root protection
- Drainage layer
- Protection board
- Soil level
- Overflow provision
- Irrigation pipes
A membrane terminated below the soil level can allow moisture to penetrate behind the waterproofing.
6. Podium Decks
Podium decks often contain multiple interfaces, including:
- Landscaping
- Walkways
- Planters
- Building walls
- Door openings
- Drainage systems
- Expansion joints
- Equipment bases
Waterproofing may eventually be covered by:
- Screed
- Tiles
- Pavers
- Landscaping
- Protection boards
Once covered, the waterproofing termination becomes difficult to inspect and repair.
Consultants should therefore clearly define all perimeter upstands before finishes and landscaping are installed.
A common risk occurs where the final landscaping or screed level is raised during construction but the waterproofing upstand remains unchanged.
The result can be a termination that ends too close to—or even below—the final finished level.
Important Coordination Point
Waterproofing heights should be coordinated with the final finished level, not only the structural slab level.
7. Equipment Plinths and Roof Bases
Mechanical equipment, tanks, solar systems and air-conditioning units are frequently installed on roof plinths.
The waterproofing should normally continue around these bases in a manner that prevents water from reaching the concrete interface.
Consultants should consider:
- Height of the plinth
- Waterproofing upstand
- Membrane termination
- Equipment fixing
- Future replacement
- Maintenance access
Where possible, waterproofing should be completed before equipment installation. Drilling through a waterproofed plinth after completion can compromise the waterproofing unless the penetration is properly detailed and resealed.
Upstand Height Alone Is Not Enough
It is tempting to solve the problem simply by increasing the waterproofing upstand.
However, the effectiveness of an upstand depends on several elements working together.
A complete detail should consider:
1. Substrate
The wall or upstand surface should be suitable for the selected waterproofing material.
2. Internal Corner
The wall-to-floor junction may require:
- Fillet
- Reinforcement
- Additional membrane
- Joint treatment
3. Membrane Continuity
The waterproofing should continue from the horizontal surface onto the vertical surface without interruption.
4. Termination
The top edge must prevent water from travelling behind the membrane.
5. Protection
The membrane must be protected from:
- Mechanical damage
- Subsequent trades
- Screeding
- Landscaping
- Maintenance work
All five elements contribute to a reliable waterproofing detail.
Do Not Determine Waterproofing Height From Structural Drawings Alone
One of the most important coordination issues occurs between:
Structural level and finished architectural level.
Consider the following example:
The structural slab is completed.
The waterproofing contractor provides a vertical upstand.
Later, the project installs:
- 50 mm screed
- 20 mm tile
- Raised paving system
- Landscaping
- Insulation system
The final finished level may become significantly higher than the original structural slab.
If the waterproofing height was measured only from the structural slab, much of the effective upstand may disappear.
Better Design Approach
Consultants should indicate waterproofing height in relation to the final finished surface or expected water level, wherever appropriate.
Waterproofing Termination – The Forgotten Detail
The upper edge of a waterproofing membrane is an important vulnerability.
If water can get behind the membrane at the termination, it may migrate between the waterproofing and substrate.
This may result in:
- Dampness
- Blistering
- Delamination
- Internal leakage
- Difficult leak tracing
Depending on the waterproofing system, termination methods may include:
- Mechanical termination bars
- Recessed chases
- Flashings
- Counter flashings
- Compatible sealants
- Protective coatings
- Render protection
The exact solution should be selected according to the membrane type, substrate and exposure.
Avoid Arbitrary Upstand Heights
It is common to see specifications stating a single waterproofing height for every area.
However, one standard height may not suit every application.
Consultants should consider:
- Expected water level
- Finished floor level
- Exposure to rainfall
- Drainage arrangement
- Ponding risk
- Splash zone
- Doorway location
- Parapet design
- System manufacturer requirements
- Applicable project standards
For critical applications, the waterproofing specialist should review the detail with the consultant before construction.
TOPKRETE Consultant Design Approach
When reviewing waterproofing upstands, we recommend evaluating the detail in the following sequence:
Water source → expected water level → finished level → waterproofing upstand → termination → protection.
Do not start by simply asking:
“How high should the waterproofing go?”
Instead ask:
“What is the highest realistic level at which water could reach this detail, and how do we prevent it from getting behind the waterproofing?”
That question leads to a more reliable design.
Consultant Upstand & Termination Checklist
Before issuing waterproofing drawings for tender, check:
- Final finished floor levels are confirmed.
- Waterproofing upstand heights are clearly shown.
- Roof parapet terminations are detailed.
- Door thresholds are coordinated with drainage.
- Balcony levels are coordinated with internal floor levels.
- Plant-room perimeter upstands are shown.
- Equipment plinths are waterproofed.
- Planter-box waterproofing extends above the critical water/soil zone.
- Membrane terminations prevent water travelling behind the system.
- Wall-to-floor junctions are properly detailed.
- Waterproofing is protected from subsequent works.
- Changes to screed or landscaping levels will not reduce the effective waterproofing height.
- All critical details are reviewed before waterproofing installation.
The Small Detail That Can Defeat a Large Waterproofing System
Imagine a 10,000 m² roof with a correctly installed waterproofing membrane.
If the entire roof membrane is watertight but water enters behind the waterproofing at one poorly detailed parapet termination, leakage may still occur inside the building.
The waterproofing material may not have failed.
The waterproofing detail has failed.
This distinction is important when investigating waterproofing problems.
Many apparent “membrane failures” are actually:
- Termination failures
- Interface failures
- Drainage failures
- Penetration failures
- Joint failures
The complete system therefore needs to be considered during both design and troubleshooting.
Conclusion
Waterproofing should never stop simply because the horizontal slab ends.
Vertical upstands and membrane terminations are critical components of the waterproofing system and should be designed with the same level of attention as the main membrane area.
Consultants should coordinate waterproofing heights with:
- Final finished levels
- Drainage
- Architecture
- Building services
- Structural details
- Expected water exposure
Most importantly, the upper edge of the waterproofing must be properly terminated to prevent water from travelling behind the system.
At Topkrete, our philosophy remains:
Waterproofing is a system, not a product.
And every upstand, termination and interface is part of that system.
Need Assistance Reviewing Waterproofing Upstands and Details?
Topkrete provides technical waterproofing support to architects, engineers, developers and specification consultants during design, tender and construction stages.
Our technical team can assist with:
- Roof waterproofing details
- Podium waterproofing systems
- Balcony and wet-area waterproofing
- Waterproofing upstand details
- Membrane termination details
- TPO/PVC membrane systems
- Crystalline waterproofing systems
- Construction and expansion joint detailing
- Waterproofing specifications
- Method statements
- Project-specific technical recommendations
TOPKRETE SDN BHD
Waterproofing • Resin Flooring • Protective Coatings
Website: www.topkrete.com
Email: info@topkrete.com