A stain appears on the ceiling inside, just below a balcony. The deck surface looks fine. The coating is not peeling. Nothing obvious is cracked. So where is the water getting in?
In our experience the answer is often the doorway, and specifically the few inches where the deck, the wall and the door opening all meet. It is the hardest detail on the whole balcony to get right, and the easiest one to cover up.
The threshold is three problems stacked on top of each other
Everywhere else on a balcony, waterproofing has one job: shed water off a horizontal surface. At the door, three things happen at once.
- A horizontal surface has to turn and run up a vertical wall.
- That vertical surface is interrupted by an opening.
- The opening has a frame fixed through it, usually with fasteners.
Each of those is a place water can be redirected inward instead of outward. Together, they are why so many balcony leaks trace back to a doorway rather than the field of the deck.
What a door pan actually does
A door pan is a waterproof tray that sits under the door threshold. Its job is to catch anything that gets past the door — wind-driven rain, water running down the frame, condensation — and carry it back out onto the deck where it can drain away.
For that to work, three things have to be true. The pan has to have upturned edges at the back and sides, so water cannot run off the inside edge. It has to be sloped or at least drained toward the exterior. And it has to be integrated with the deck waterproofing and the wall weather barrier in the right order, so every layer sheds onto the one below it rather than behind it.
Get the order wrong and the pan becomes a reservoir instead of a tray.
Where it usually goes wrong
A few patterns come up repeatedly.
The deck was coated up to the door, not under it
The waterproofing stops at the threshold and the door sits on bare substrate. Anything that reaches the threshold has a direct path into the framing.
The pan has no back dam
A flat piece of flashing under a door is not a pan. Without an upturned back edge, water that collects in it runs straight into the floor assembly.
The layers are lapped the wrong way
Weatherproofing works like roof shingles: each layer has to overlap the one below it on the outside. When a pan is tucked behind the deck membrane instead of over it, or the wall barrier is lapped under the pan flange, water is actively directed inward.
The threshold was sealed with caulk alone
Sealant has a service life, moves differently from the materials either side of it, and is usually the only thing holding back water at that joint. It is a finishing detail, not a waterproofing system.
Why the stain is not directly below the leak
Water that gets past a threshold lands on framing. Framing runs horizontally. The water travels along a joist, a ledger or a layer of sheathing until it reaches somewhere it can drip — a light fixture, a seam in the drywall, the low point of a sloped ceiling.
That is why chasing the stain rarely finds the source, and why a repair aimed at the stain often changes nothing. The useful question is not “where is the ceiling wet” but “what is uphill of it”.
What a proper repair scope should cover
If the doorway is implicated, the written estimate should say what happens there, not just what happens to the deck surface. At minimum it should address:
- How far back the existing surface is removed to reach the threshold.
- Whether the substrate under and around the door is sound, and what happens if it is not.
- What pan or flashing is being installed, and how it integrates with the deck membrane and the wall barrier.
- How the door is reset, and whether the frame has to come out to do the work properly.
- What is restored afterwards — stucco, trim, paint, threshold finish.
If a quote for a leaking balcony only describes preparing and recoating the deck, the doorway has not been addressed.
A note on what can be known before work starts
Some of this is visible from the surface. Much of it is not. The condition of the substrate, the state of the pan, and the order the layers were installed in are usually hidden until an area is opened up.
A good proposal is honest about that: it sets out what has been observed, what is being assumed, and how additional work will be handled if opening the area shows something that could not be seen beforehand. Anyone who can tell you the full extent of a concealed repair from a photograph is guessing.
Related reading
If the problem looks like it sits in the deck surface rather than the doorway, our deck and balcony waterproofing page covers how we approach those repairs. Where the wall is involved, see stucco and deck-to-wall repairs.
Questions homeowners ask
Can you find the leak without opening anything up?
Sometimes. Visible conditions, the pattern of when water appears, and the location of staining often point clearly at a source. But materials that remain covered limit what can be established, and some conditions are only confirmed once an area is opened.
Will recoating the deck stop a leak at the door?
Only if the coating was the problem. If water is entering at the threshold, a new surface over the same detail leaves that path in place.
Does the door have to be removed?
Not always. It depends on how the existing pan and flashing were installed and how much of the detail has to be rebuilt. The written scope should say which approach is proposed and why.
How long does this kind of repair take?
Project timing depends on the repair scope, access, weather and material requirements. We discuss the expected schedule for your project before work begins.
Do you charge to look at it?
No. Estimates for proposed repair work are free and include a written description of the work and the price.
Seeing a stain below a balcony? Tell us what you are noticing and where the property is, and we will explain the likely source before quoting anything. Call (310) 590-5769 or request a free estimate.