Stains below the terrace door
The classic sign of an unflashed door sill.
Roof deck and terrace waterproofing in New York, NY
A terrace is a roof with furniture on it. When it leaks, the fix is almost never on the surface you walk on; it is the membrane and drainage underneath.
- We answer 24/7
- Pavers and wood decks
- Membrane and drains rebuilt
Quick answer: Terrace leaks in New York, NY usually come from the waterproofing under the pavers or decking, not the walking surface: a failed membrane, a clogged drain hidden below, or a door sill with no flashing. The repair means lifting the surface, rebuilding the membrane and drainage, and relaying it.
What the job involves
What sits under a terrace
A well-built terrace is layers: a structural deck, a waterproof membrane turned up the walls and under the door sills, a protection or drainage layer, then pavers on pedestals or a wood deck on sleepers. Water is meant to pass through the walking surface and drain away on the membrane below.
Most terrace leaks start where those layers meet something else: the door threshold, a railing post, a planter, or a drain buried under pavers and clogged with years of grit. Finding which one takes lifting part of the surface, not guessing from below.
Cost factors
What terrace waterproofing costs depend on
Removing the surface
Pavers lift out. Decks built in place take longer to take apart.
Membrane condition
A spot repair or a full new membrane under the terrace.
Door sills and walls
Turning the membrane up under thresholds can mean adjusting doors.
Drains
Buried drains cleared, replaced or added.
Pedestals and protection
New pedestals, pads or drainage mat under the surface.
Relaying
Resetting pavers level or rebuilding deck sections.
Variations of the job
Terrace work we do
Paver terraces
Pavers on adjustable pedestals are lifted, numbered and stacked, the membrane is repaired or replaced, drains are cleared, and the pavers are reset level. Pedestals also keep pavers from grinding into the membrane.
Wood deck over membrane
Decking is built in removable sections on sleepers resting on protection pads, never screwed through the membrane. Where an old deck was fastened through the roof, those holes are the leak.
Leaks below a terrace
Water in the apartment below often comes from the door sill, where many terraces were built with no flashing turned up under the threshold. We rebuild that detail as well as the field of the terrace.
Local conditions
Railings, decks and historic districts
Adding railings or a deck changes what a roof looks like from the street, which matters on historic blocks. Park Slope's historic district shows how it usually goes: when rooftop work there, railings included, cannot be seen from the street, Landmarks has handled it as a Certificate of No Effect rather than a full public review. We check which path a new terrace on your building would take before the design is fixed.
Timing
How long a terrace is out of use
A repair at one door sill or drain can often be done in a day or two, with the surface lifted only around it. A full rebuild under a large terrace takes longer, because the pavers or decking come off, the membrane is replaced, and everything is reset.
Weather matters too. Membranes and liquid flashings need dry conditions to bond, so a rainy week stretches the schedule. The work is planned so the terrace is watertight at the end of every day, even when it is not yet usable.
How it runs
How a terrace gets rebuilt
- 1
Find the leak
Water test at sills, walls and drains before lifting everything.
- 2
Lift and store
Pavers or deck sections removed and protected.
- 3
Rebuild the waterproofing
Membrane repaired or replaced, turned up walls and under sills.
- 4
Drainage layer
Protection board or drainage mat, drains cleared and tested.
- 5
Relay the surface
Pavers on pedestals or deck sections on sleepers, set level.
Warning signs
Signs a terrace is leaking
Water that pools and stays
A buried drain is clogged.
Pavers rocking or sinking
Pedestals have shifted or something below has failed.
Soft or rotting deck boards
Water is not draining away underneath.
Roots and soil in the drains
Planters shedding into the drainage.
White deposits on walls below
Salts left where water moves through masonry.
Questions we hear
Roof deck and terrace questions
Rarely for good. Sealers on top of pavers do not stop water that reaches the membrane below. The waterproofing has to be repaired where it failed.
Door sills are where the membrane most often stops short. Water running on the membrane reaches the threshold and gets in under it.
For waterproofing, usually. Pedestals keep pavers off the membrane, let water drain freely, and let pavers be lifted for repairs without breaking them.
Yes, on protection pads, with drainage that does not wash soil into the roof drains. Planters fastened through the membrane or sitting straight on it cause leaks.
It can. Structural checks, Department of Buildings filings, co-op or condo boards and, in historic districts, the Landmarks Preservation Commission may all apply, depending on the building.
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Learn moreTerrace leaking into the apartment below?
Call and we will find where the water gets past the waterproofing.