Stucco News

Question and answers on Stucco and Plastering

December, 2015

More about leaking chimneys


When a chimney is leaking or failing, usually the only solution is to re-do the
whole chimney, at least from the roof line up.

The main sources of chimney leaks are from the flashing, the metal that covers the gap between the
chimney and the roof, and the cap, or the mortar that covers the very top of the chimney.

These are the main causes of failure and the reason for almost all our chimney jobs.

Two other sources of failure are a lack of a kick out flashing, where a gutter butts to the chimney,
and the shoulder, or the angled part that connects the narrow part at the top to the wide part at the bottom.

The loose and damaged stucco on the chimney is a result of a leak and not a cause of the leak.

Leaking stucco
                            chimney in Washington, DC

The solution someone had in the past was to
coat the bricks above the roof with thoro seal.
Of course, this didn't stop the leak.

The thoro seal was peeling and popping
because the cap, or the mortar on top was deteriorating.

How we corrected it is here:

Rotten stucco chimney
                            in Chevy Chase

This chimney was just stuccoed
6 years before we got here.

A kick out flashing, or a small piece
of sheet metal, would have prevented
this failure.

A kick out flashing deflects water
from the chimney flashing into the gutter.

Rescueing an old
                            historic stucco chimney in Washington, DC
You may have seen this chimney on my site here:

The old flashing on this Spanish tile roof was never put on tight to the substrate, in this case, terra cotta blocks. The more the stucco deteriorated, mainly due to deteriorating mortar on the cap,
the more the chimney leaked.

The stucco is cut off to the block and
flashing is put on over the old flashing. What we are doing is building a little roof.
When we stucco the chimney, mortar overlaps the flange on our counter flashing.
Someone's solution in the past was to put a big glob of goo around the base of the chimney, which did nothing, but waste goo.
Deteriorated chimney
                            in Washington, DC

Just because a chimney looks
fine from the ground doesn't mean it is alright.

I took this picture from my scaffold
of the next door neighbor's chimney,
when we were working in Northeast
Washington, DC.

I never showed him, because I
didn't want to make him feel bad.

This is a good candidate for stucco.

Probably the only reason it hasn't collapsed is because the mortar
has washed out between the bricks
allowing water to escape.

I bought a drone with a camera for only 40 dollars and it is a great tool for inspecting chimneys.
We were working in Arlington, Virginia stuccoing a chimney when a man stopped to ask me what was wrong with his chimney. His brick chimney was leaking and someone talked him into putting on one coat stucco basecoat and a a synthetic finish for a solution. After $ 2,000 his chimney was still leaking.
I explained that the mortar cap and the flashing were the cause of his leak, and there was no need to
stucco over the brick. This is my competition for you. Water runs downhill always. It doesn't travel horizontally through brick.