The short answer
Chimney waterproofing protects brick and mortar from absorbing rain and snow, which causes cracking, flaking and leaks over time. AshVanta inspects the chimney, repairs the crown, flashing and mortar as needed, and applies a breathable, vapor-permeable water repellent so moisture stays out but can still escape.
Brick and mortar look solid, but they absorb water. In New York, rain, wind-driven storms, snow and repeated freeze-thaw cycles push moisture into a chimney all year. When that water freezes, it expands and slowly breaks the masonry apart from the inside. Over time this leads to crumbling mortar, flaking brick, rusted dampers, stained ceilings and, in bad cases, a chimney that has to be partly rebuilt. AshVanta Chimney Services waterproofs chimneys for homeowners in New York City and nearby cities. Our certified technicians find where water is getting in, fix the problems a sealant can't cover, and apply a breathable water repellent. The repellent keeps rain out but still lets moisture inside the masonry escape. This page explains the warning signs, what the service includes, how we work, and what affects the cost.
Signs you need it
Water damage in a chimney usually shows up slowly. You may notice it inside the fireplace, on the outside brick, or on the walls and ceiling near the chimney. If you see any of the signs below, it's worth having the chimney looked at before the damage spreads.
- White, chalky staining on the outside brick, called efflorescence, left behind as water moves through the masonry and evaporates
- Brick flakes, crumbled mortar or small debris collecting in the firebox
- Water, drips or rust stains in the firebox or on the damper
- A musty or strong creosote smell, often worse on humid or rainy days when moisture mixes with deposits in the flue
- Brick faces popping off or breaking away, known as spalling
- Damp spots or peeling paint on walls or ceilings next to the chimney
What's included
A sealant only works if the chimney underneath it is sound. Every waterproofing job starts with finding out why water is getting in. Then we handle the repairs that need to come before any sealing.
- Inspection of the chimney exterior, crown, flashing, cap and visible flue
- Camera inspection of the flue when we suspect water damage inside
- Cleaning loose dirt, moss and efflorescence from the brick so the repellent can bond
- Notes and photos of cracked mortar joints, spalled brick, or crown and flashing problems
- Repointing and minor masonry repairs when needed, agreed with you before we start
- Crown crack sealing, or a crown coating where the crown is still sound
- Flashing sealing where the chimney meets the roof
- Applying a breathable, vapor-permeable water repellent to the exposed masonry
- Checking that a chimney cap is in place to keep rain out of the flue
- Cleanup and a walkthrough of what we found and what we did
How we work inside your home and on the roof
Most waterproofing happens on the roof, but we usually check the inside of the chimney too. Before we work at the fireplace, we lay drop cloths from the door to the hearth. We seal the fireplace opening and run HEPA vacuums so soot and masonry dust stay out of your living space. If the flue needs sweeping before we can see it clearly, we use rotary brushes. A camera lets us look for cracked flue tiles, gaps in the joints and water staining you can't see from below.
On the roof, we set up safe access and protect shingles and gutters where we step and stage materials. We clean the masonry before treating it. We only apply repellent when the brick is dry and the weather fits the product's requirements, because sealing damp masonry traps moisture inside. We don't use paint or non-breathable coatings on brick, since they hold water in and can make spalling worse.
Time for your annual chimney check?
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 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 include a Level 1 inspection. We'll tell you if what we find calls for a higher level.
Moisture matters even more for chimneys that vent gas appliances. When a New York City building converts its boiler from oil to gas, the chimney has to be evaluated as part of the work. A new liner is often needed because gas exhaust produces acidic condensate that can corrode a masonry flue. Water getting in from outside adds to that damage.
Timing matters too. New York City's heat season runs from October 1 through May 31. Scheduling waterproofing in late spring, summer or early fall avoids cold-weather application problems and gets the chimney ready before heavy use.
What affects the price
Every chimney is different, so we price after we've seen it. These are the main factors:
- Chimney height, roof pitch and how hard it is to reach the roof
- Fuel type the chimney serves: wood, gas or oil
- Flue size and condition, including cracked tiles or a missing liner
- How much soot, creosote or debris has to be cleared before inspection
- Whether a camera inspection is needed
- How much masonry, crown or flashing repair has to come before sealing
How a visit works
When you contact us, we ask about the chimney, the fuel it serves and any leaks or staining you've noticed. Then we schedule a visit. Our technician inspects the chimney and shows you photos of any problems. You get a clear explanation of what needs repair and what can be sealed. We don't start any repair work until you've agreed to it.
Once the work is approved, we make the repairs, let any new mortar cure as needed, and then apply the water repellent in suitable weather. At the end, we clean up the work areas and walk you through what we did.
