On many roofs, the large flat area gets most of the attention.
It is easy to see.
Easy to measure.
Easy to price.
But the most critical waterproofing areas are often not horizontal.
They are vertical.
Upstands, parapets, kerbs, penetrations, thresholds and changes in level are where the waterproofing system has to work much harder.
Why?
Because these details combine several risks at the same time:
- Changes in direction
- Movement between different materials
- Corners and terminations
- Mechanical fixings
- Difficult access
- Water concentration
- Increased workmanship dependency
A large flat membrane can often perform very well.
But one poorly prepared upstand can compromise the whole roof.
The square metres do not tell the whole story.
Typical problems include:
- Insufficient upstand height
- Poor adhesion to vertical surfaces
- Weak internal or external corners
- Incorrect termination
- Gaps behind flashings
- Incompatible substrates
- Poor reinforcement around changes in direction
- Water tracking behind the waterproofing layer
This is why vertical detailing should never be treated as an afterthought.
Before installation, we should ask:
- Is the upstand high enough?
- Is the substrate suitable and stable?
- Does the detail require reinforcement?
- How will the membrane terminate?
- Are corners properly formed?
- Can water get behind the system?
- Is there enough space to install the detail correctly?
The flat area may represent most of the square metres.
But the details often determine whether the roof succeeds or fails.
The membrane protects the area.
The details protect the system.