Chimney question

Inspection yesterday - chimney brick was did colored from roofline up. Sort of a greyish/white. Chimney was used for gas furnace & gas hot water heater. Could not see a metal sleeve in the clay flues tiles. Is the most likely cause condensation from inside the chimney wicking through the brick??

In a day and a half, no comments? Well, I don’t know the answer but I know a lot of people troll me, so I’ll leave this comment and see if someone can help you.

Thanks Russell. Been meaning to message you. We spoke by phone roughly a year ago. I acted on your marketing suggestions and I’m seeing the results (starting to surpass my target numbers actually). Thank you very much for taking the time to speak with me.


Any pics?

Sounds like efflorescence.
Flowering minerals.
Soluble salts.

Look at the crown for crack/s! I start at the Crown/liner/s, cap, spark arrester, and work down the chimney wydth, shoulders, ash pit, if any and lastly the base.

Crown questions to ask; a. Does the crown protrude 4 inches from the masonry walls? b. Is there a capillary break in the crown? c. is the crown / masonry intersection intact? d. Are/is the flue liner/s sealed at the concrete flue intersection? e. Do/does the flue/s extend 4" inches above the crown?

Hypothesis; from the roofline up usually means chimney water infiltration at the crown.

When/while inspecting masonry chimney’s; Observe the brickwork mortar bonds. The Bed, Head and Butt joints.
Even a hair line crack allows water to enter the masonry chimney chase.

Thanks Robert. If it were water coming into the chimney system from above, would it not be more endemic throughout the chimney structure? This was maybe the first 5’ down from the top on all 4 sides?

you are welcome.

Good point.
Taking gravity into consideration one would think so.

Too many if’s to use.
It also depends upon how the masonry and chimney are structured.

Here is one example
1: When the leak starts is at the crown, bulk water is absorbed into the mortar ooze and bricks.
Over time, gravity works the water several courses down.
1 a. Not enough water to penetrate lower.
1 b. not enough water vapor to do any damage.

Over time is will go lower.

Zny pics?

Sounds like a moisture issue, likely condensation, the cause depending heavily on flue configuration.

Think of this, if it was water coming in the chimney from below, and only appearing above the roofline, I suspect the homeowner may have moved out by then. Ha ha ha

cadalian, think of the amount of air movement rising out of the brick chimney flue even when there is no solid fuel being burnt.
bricks can reach 63°C or 145.4F.
100 feet of brick can expand 1" inch.

When you add to that the mechanical design of a clay brick masonry chimney and the mortar ooze, efflorescence below the crown and above the roofline is most common.
Mostly water enter between the concrete and flue liners.
That starts the degrading process.

Sorry for the edit.
cadalian, NOTE: a chimney crown must slope away from the flue/s.
The crown base 4 inches wider than the chimney and the top angled 15% from the center downwards.
So water runs off the crown.
Under the crown there is a capillary break, like a window sill.
Remember, water travels downstream, along the vertical face, and under the crown.
The capillary break, a curff, cut stops water from traveling under the crown or even upstream and backwards onto to the bricks.

When efflorescence is below the roofline it is likely degraded/poor quality mortar and cracked mortar bonds.