The short answer
Chimney waterproofing applies a vapor-permeable water repellent to clean, sound masonry so rain can't soak into the brick and mortar, while trapped moisture can still escape. It works best after an inspection and any needed repairs to the crown, mortar joints and flashing, because sealer will not stop water coming through cracks or gaps.
Brick and mortar look solid, but they are porous and absorb water every time it rains. On Staten Island, wind-driven coastal rain followed by winter freeze-thaw cycles works water deeper into the masonry each year. Water inside brick expands when it freezes, which cracks mortar joints, pops the faces off bricks, rusts dampers and stains ceilings. Chimney waterproofing seals the outside of the chimney with a breathable water repellent. Rain beads off, and moisture already inside the brick can still dry out. CrestFlue Chimney Service waterproofs chimneys for homeowners across Staten Island and nearby communities. Before any sealer goes on, we inspect the chimney and handle the repairs that waterproofing alone cannot fix.
Signs you need it
Water damage in a chimney usually shows up slowly, and often far from where the water actually gets in. If you notice any of these, have the chimney looked at before the next winter.
- White, chalky staining on the brick (efflorescence), which is salt left behind as water moves through the masonry
- Water, rust or puddling in the firebox or on the damper after a storm
- Brick flakes, crumbled mortar or small chunks of masonry collecting in the firebox
- Brick faces popping off or spalling on the outside of the chimney
- A stronger smoke or creosote smell in humid or rainy weather, which happens when moisture mixes with deposits in the flue
- Damp spots, peeling paint or stains on the ceiling or walls next to the chimney
- Mortar joints that are recessed, cracked or sandy to the touch
What's included
Every waterproofing visit starts with finding where water is getting in. Sealer is only one part of the job. A chimney with a cracked crown or loose flashing will keep leaking no matter what is sprayed on the brick.
- Visual inspection of the chimney exterior, crown, cap, flashing and firebox
- Camera check of the flue when water damage inside the chimney is suspected
- Cleaning loose debris, moss and dirt from the masonry surface
- Checking that the brick is dry enough to accept sealer
- Pointing out mortar joints, crown cracks or flashing gaps that need repair first
- Covering roofing, siding and windows near the work area
- Applying a breathable, vapor-permeable water repellent to the brick and mortar
- Final walkthrough with photos and notes on anything to watch
How our crew works in your home and on the roof
Most of the waterproofing work happens outside, but we often need to check the firebox, damper and flue from inside. Before we open anything, we lay drop cloths from the door to the fireplace and run HEPA vacuums to catch soot and debris. If the flue needs a sweep before we can see it clearly, we use rotary brushes with the vacuum running so dust stays in the chimney and out of the room. When water damage is suspected higher up, a camera lets us see the liner and flue tiles without opening anything.
On the roof, our certified technicians set ladders and fall protection, then protect shingles and nearby surfaces before cleaning the brick. The water repellent goes on with a low-pressure sprayer so it soaks into the masonry instead of running off. We use breathable products only. Paint and non-breathable coatings trap moisture inside the brick and can speed up spalling.
Weather matters. Sealer needs dry masonry and a dry forecast to cure, so we may reschedule if rain is coming.
The standard we follow
The NFPA 211 standard calls for chimneys, fireplaces and vents to be inspected once a year. Chimney professionals use three inspection levels. Level 1 applies when nothing about the system has changed. Level 2 applies when the system changes, such as a new appliance or a switch of fuel, or when the home is sold. Level 3 applies when a hidden hazard can only be reached by opening part of the chimney or building.
Waterproofing ties into that annual inspection. Water is one of the main reasons chimneys deteriorate, and catching early damage during a routine inspection is easier than repairing a failed crown or a crumbling stack. If your home has switched from oil to gas heat, keep in mind that gas exhaust produces acidic condensate that can corrode a masonry flue. A new liner is often needed in that situation, and it is a separate issue from exterior waterproofing.
What affects the price
We give you a clear quote after we see the chimney. These are the main factors:
- Chimney height, roof pitch and how easy it is to reach the stack
- Size of the chimney and how much masonry surface needs sealing
- Fuel type and the condition of the flue, especially if water has already damaged the liner
- How much dirt, moss or buildup must be removed before sealing
- Whether a camera inspection is needed to trace a leak
- Whether repairs to the crown, mortar joints, cap or flashing are needed first
How a visit works
You contact us and describe what you are seeing: stains, water in the firebox or flaking brick. We schedule a visit and check the forecast, since the masonry needs to be dry.
On the day of the visit, the crew protects your floors, inspects the chimney inside and out, and shows you what we found. If repairs are needed before waterproofing, we explain them and give you a quote before doing any extra work. Once the chimney is sound, we clean and seal the masonry, clean up, and walk you through photos of the finished job.
Many homeowners book waterproofing in spring or late summer so the work is done before New York City's heat season starts on October 1 and the fireplace or heating system sees regular use.