The short answer
Chimney waterproofing seals the brick, crown and flashing so rain and snow can't soak into the masonry and cause leaks, cracking and flaking. We inspect first, fix the entry points, then apply a breathable water repellent that keeps water out but lets trapped moisture escape.
Water causes more chimney damage than fire. Rain and snowmelt soak into brick and mortar, then freeze and thaw through a New York winter, and the masonry slowly cracks, flakes and loosens. Leaks also rust dampers, stain ceilings and walls, and can weaken the flue liner. Nexora Chimney Services waterproofs chimneys for homeowners in New York City and nearby cities. Our certified technicians first find where the water is getting in, then seal the masonry with a breathable water repellent so moisture stays out while the brick can still dry. Waterproofing works best on a chimney that is sound, so every job starts with an inspection. Repairs to the crown, flashing or mortar come before any sealant.
Signs you need it
Water damage usually shows up slowly. A homeowner notices a stain or a puddle months after the problem started. If you see any of the signs below, have the chimney checked before the next freeze-thaw season.
- White, chalky staining on the outside brick. This is efflorescence, a mineral residue left behind when water moves through the masonry.
- Water, damp ash or rust streaks in the firebox after rain
- Brick flakes, crumbled mortar or small debris collecting in the firebox or on the smoke shelf
- A musty, damp smell from the fireplace, or a stronger creosote odor on humid or rainy days
- Spalling bricks, where the face of the brick pops off and leaves a rough, pitted surface
- Water stains on the ceiling or wall next to the chimney
- A rusted damper or firebox parts that stick or won't close fully
- Poor draft or a smoky fireplace, which can happen when a damaged crown or flue lets water and debris in
What's included in a waterproofing service
Waterproofing is more than spraying the outside of the chimney. Sealant applied over a cracked crown or failed flashing won't stop a leak, so we check and address each place water can enter. Before we start any repair, we explain what we found and what it involves.
- Chimney inspection at the right level for your situation, with written notes and photos
- Video camera inspection of the flue when we see signs of internal water damage
- Check of the chimney crown for cracks, gaps and poor slope, with sealing or repair as needed
- Check of the flashing where the chimney meets the roof, with resealing or repair as needed
- Check of mortar joints and repointing of failed joints before sealing
- Chimney cap inspection, or installation of a cap if the flue is open to rain
- Cleaning of the masonry surface, including efflorescence and loose debris
- Application of a vapor-permeable water repellent made for masonry chimneys
- Cleanup inside and outside the home, and a review of the work with you
How our crew works on the roof and in your home
On the roof, the crew sets up safe access and looks over the crown, cap, flashing and every face of the brick. We use a breathable, water-based or siloxane-type repellent designed for masonry. It soaks into the brick and mortar without forming a film, so water vapor from inside the chimney can still escape. Paint or a non-breathable coating traps moisture and can make spalling worse. We apply the repellent only when the brick is dry and the weather and temperature allow it to cure, so roof work sometimes has to wait for the right day.
Inside, we lay drop cloths from the door to the fireplace and cover the hearth. When the flue needs cleaning or a camera inspection, we use rotary brushes and run HEPA vacuums to keep soot and dust out of your living space. The camera lets us see cracked liner tiles, gaps in the mortar joints and water damage that can't be seen from the firebox or the roof.
Water damage can also start inside the flue. When a New York City building switches its boiler from oil to gas, the chimney has to be evaluated, and a new liner is often needed. Gas exhaust produces acidic condensate that can corrode a masonry flue. If we see that kind of damage, we'll tell you.
Time for your annual chimney check?
The standard we follow
Our work follows NFPA 211, which calls for chimneys, fireplaces and vents to be inspected once a year. The industry uses 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. Most waterproofing visits start with a Level 1 or Level 2 inspection, depending on your chimney's history.
What affects the price
Every chimney is different, so we quote after we've seen it. The main factors are:
- Chimney height, the number of exposed faces, and how easy the roof is to reach
- Fuel type and how the chimney is used: wood, gas or oil
- Flue size, the number of flues, and the condition of the liner
- How much soot, creosote or debris has built up if cleaning is needed
- Whether a camera inspection is needed
- Repairs needed before sealing, such as crown work, flashing, repointing or a new cap
How a visit works
You book a time and tell us what you've noticed, such as stains, leaks or flaking brick. The technician arrives, protects the work area and inspects the chimney from the inside and the roof. We show you photos, explain where water is getting in, and walk you through the recommended work before anything begins. Small repairs and sealing can often be done the same day if the weather is dry. Larger repairs may need a second visit. When we finish, we clean up and review the work with you.
New York City's heat season runs from October 1 through May 31. Owners who need a working chimney or boiler flue in winter should schedule waterproofing in late spring, summer or early fall, when dry weather makes curing more reliable.
