What a chimney leak looks like from inside the house

From the inside, a chimney leak usually looks like a brown ring on a ceiling near the chimney breast, a damp patch on the wall of an upstairs bedroom, paint or wallpaper lifting on the chimney breast itself, white powdery staining on the brick where the stack passes through, or a damp smell in the fireplace that gets worse after rain. It rarely looks like water running anywhere, which is why it is often found months late.

A chimney leak usually arrives as a water damage call about a ceiling. The water came in at the roof, traveled along a joist and appeared in the room below, several feet from where it entered.

The four common paths for rain into a house through a chimney

• The crown, the sloped concrete cap on top of the stack. It cracks with age and lets water straight into the masonry below it.
• The cap or rain cover over the flue opening. A missing or damaged cap means rain goes directly down the flue, and it also lets birds and debris in.
• The flashing, the metal that seals the joint where the chimney passes through the roof. Lifted, corroded or poorly sealed flashing is one of the most common roof leaks in any house.
• The masonry itself. Brick, concrete and stone are naturally porous, so unsealed masonry absorbs water, and masonry exposed to repeated water can crack, craze, spall or disintegrate through freeze thaw cycling.

That last one explains why chimney damage tends to show up in spring. Water absorbed in fall freezes in winter and expands, and the brick that survived December fails in March.

How to tell it apart from a plain roof leak

None of these tests is conclusive on its own, which is what an inspection is for, and together they are usually enough to know what to ask about.

1. Where is the stain relative to the chimney breast? A stain that follows the line of the stack through the house points at the chimney rather than at the field of the roof.
2. Does it appear after wind driven rain in particular, or after any rain? Flashing and crown leaks often need the rain to arrive at an angle.
3. Is there a damp smell in the firebox after rain, or a change in how the fire draws? Water in a flue changes both.
4. Is there white powdery staining on the brick, inside or outside? That is a sign of water moving through the masonry and leaving salts behind as it dries.
5. Is the ceiling stain fresh at the edges each time it rains, or is it an old, dry, sharply defined mark? A stain that grows is an active leak.

There is a fifth question people forget: is there anything above that ceiling other than the chimney. Bathrooms, condensate lines from air conditioning and roof valleys all produce ceiling stains, and a competent look at the inside of the house rules them out before anyone climbs anything.

Why the wet material is the urgent half

The leak is the cause and it needs fixing. The wet plaster, the wet insulation and the wet framing are the part with a clock on them. The EPA advises drying water damaged areas and items within 24 to 48 hours to prevent mold growth, and a ceiling cavity that has been quietly wet through several rainstorms is well past that window.

Plaster and masonry are class 4 materials under the water damage standard, ANSI/IICRC S500, which means water is bound inside them and comes out slowly. They are read with meters, never by touch, and they take longer than drywall to reach a dry standard.

What an inspection should look at

The three inspection levels come from NFPA 211. A level 1 covers the readily accessible parts of the chimney and the appliance connection. A level 2 adds the accessible areas of the attic, crawl space and basement and a video camera scan of the flue interior, and it is what a property sale or an event that may have caused damage calls for. A level 3 opens part of the building or the chimney where a concealed hazard is suspected and cannot be evaluated any other way.

For a leak with a stain already showing, the attic and the flue scan of a level 2 are usually the useful part, because that is where the water track can be seen. The levels are set out side by side in Level 1, level 2 and level 3 chimney inspections compared.

What a homeowner can do today

• Photograph the stain with something in the frame for scale, and photograph it again after the next rain. The comparison tells you whether it is active.
• Look in the attic with a flashlight during or just after rain, if you can do it safely, and note where the water track sits relative to the chimney.
• Move anything absorbent away from the wall or ceiling below the stain.
• Do not paint or seal the stain until the source is dealt with.
• Do not use bleach on the wet plaster. The EPA does not recommend a biocide such as chlorine bleach as a routine practice, and it does nothing about the water still in the material.

Where this sits with DHL

The water damage side of this is the everyday work: assessment, moisture mapping, drying to a dry standard with readings logged daily, and documentation photographed for the carrier. That method is on the Water Damage Restoration page, and the same team covers Morris County, Bergen County and the four other counties.

Start on the water side, because the wet plaster and the wet framing above the stain are the half with a clock on them. The chimney scope, including the crown, cap and flashing work behind most of these leaks, is on Chimney Repair.

This article is about Chimney Repair.