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The information below, while specific to Hollin Hills, also applies to Hollin Hall and other homes that have chimneys constructed of used brick.


One of the unique design features in Hollin Hills homes is the chimney.

Beyond adding an interesting design element, the chimney serves a dual function, housing the fireplace and flues, as well as offering a structural mass to brace the house against wind loading. Brick chimneys pose a special set of practical problems for the homeowner.


Their
way

                                   
Click images for larger view
 
The unsightly "tin cap" fix.                      Tin cap with bad brick patch job.


Our
way
(detail)
    Chimney       
Click images for larger view
 
New cap, drip edge, pointing, and counter flashing.  Click here for detail.
Please note: new mortar color matches old.


Click image for larger view
Chimney with new sloped brick cap.


Click image for larger view
Chimney repointed from roofline up.

These brick chimneys often experience several interrelated problems due to the nature of the material and the design of the chimney. Typical problems include leaking between the chimney and the roof, water staining on the interior (living room) face of the brickwork, blistering paint and plaster where the ceiling meets the chimney, leakage into the wood box and/or fireplace, crumbling brick, and a disintegrating chimney cap.  Many chimneys experience a combination of the problems above. All of these problems are caused by water entering the chimney structure through defects in the masonry, and through the flashing at the roof/chimney joint.

Used Brick. To comprehend the problems and solutions, one must understand the structure and the material of the chimney. Brick chimneys are typically a hollow column of brick, enclosing the clay flue pipes from the fireplaces and in some cases, the furnace flue pipe. The top of the chimney has a mortar cap. Most brick in Hollin Hills, Hollin Hall and the surrounding neighborhoods is what is known as “used brick”. As the name implies, used brick is salvaged from the demolition of older buildings and is generally a mix of brick from different sources.  The bricks in this area are from demolished buildings in DC and Baltimore. The original walls from which the bricks were salvaged were occasionally painted, thus the paint remnants on some bricks.


When this brick  was originally manufactured (around the turn of the century and before) the kiln baking process was uneven. In the kiln, brick close to the heat source was baked hotter and ended up harder with a dark red color. Brick that was further from the heat source was baked less and thus is softer and has a lighter, salmon color. These “salmon” bricks were originally used on interior walls and were never intended to be exposed to the weather. Their softness allows them to absorb moisture, and when that moisture freezes in the winter, the expansion of the water into ice causes the surface of the brick to flake off. Over time, the entire brick can flake away to nothing.


Unfortunately, when Hollin Hills, Hollin Hall, and some of the surrounding neighborhoods were built, these salmon bricks were indiscriminately mixed with the darker brick. Virtually every chimney built with used brick has exposed salmon brick. Other exterior walls also have salmon brick, but this is a less serious problem as the bricks are shielded from the weather by the roof overhang. Disintegrating brick (a problem in itself) also allows water to penetrate the chimney structure and cause other problems. The fix for the crumbling brick is to cut out the bad brick, and replace it with a non-salmon brick. In any given chimney, there may be just a few bricks that need replacing, or there may be dozens.


Chimney cap. The top of the chimney is covered with a cap of mortar which has often developed cracks. The porosity of the mortar and the cracks allow water to penetrate both the brickwork and the chimney cavity. A leaky cap is often the source of water dripping into the wood box and fireplace. In cases where the cap is extremely deteriorated, it should be replaced. To improve longevity, when replacing the cap, we use reinforced concrete rather than mortar. The new cap can also overhang the edge of the brick by an inch to provide a lip so water running from the cap drips clear of the chimney rather than running down the face of the brickwork. In cases where the chimney cap is fairly intact, we coat it with black roof cement (looks like tar) to make the cap waterproof. Where a replacement cap is not necessary, water can be diverted from the sides of the chimney by adding a small metal drip lip. We add this lip on all four sides of the chimney by cutting a slot into the brick around the top edge of the chimney. The drip lip is fairly unobtrusive when painted black to match the tar coating the cap. Our subtle drip lip is not to be confused with the unsightly tin lids with which so many Hollin Hills Chimneys have been disfigured.

Pointing. As described above, leaky chimney caps allow water to seep into the top rows of brick. Through repeated freeze/thaw cycles, this moisture causes the bricks and mortar in the top few feet of chimney to separate from each other. The separation creates cracks around the top of the chimney that allow even more water into the brickwork, thus accelerating decay. As water penetrates through the leaking cracks, leaking cap, and crumbled bricks and seeps downwards, it evaporates through the brick surface, leaving a white calcium residue on the brick face.  Many hoemowners are familiar with this residue on their living room chimney wall. Our solution to the cracked joints is to grind out the cracked mortar and replace it with new mortar. This process is called pointing. Typically, only the top foot or two of the chimney needs to be pointed but in some cases, more pointing is necessary. We make sure the color of the new mortar is similar to that of the original mortar through careful combination of different sand colors and different cement colors.  Most of the original mortar over time has darkened with dirt and mildew so it may take some time for the new mortar to acquire that aged patina. Alternatively, the entire chimney can be acid washed so all of the mortar looks clean.

Flashing.  The final challenge with chimneys is the flashing joint between the chimney and the roof. The typical roof has a piece of sheet metal (flashing) that is embedded in the roof tar or shingles and runs up the face of the brick ten inches or so. The top edge of this metal is sealed to the brick with caulk or tar to prevent water from running down the brick behind the metal. However, the durability of this seal is entirely dependent on the integrity of the caulk. As soon as the caulk cracks or peels away from the brick, water can get behind it. A typical scenario is that the caulk joint crosses a crumbling salmon brick and the caulk peels away with the flakes of brick. The water running down from the top of the chimney and down the face of the brick is then funneled behind the flashing and the water continues its downward path, eventually running down the face of the brick inside the house. At the point where the ceiling meets the brick, the water soaks into the plaster, causing the plaster to flake and crumble and the paint to blister and peel. The water also continues to flow down the face of the chimney, leaving water stains, and in extreme cases, puddles on the floor. The typical roofer/handyman solution is to smear more tar over the flashing joint, which usually solves the problem only for the short term. The permanent solution we use is to cut a slot into the brickwork above the flashing, and install another piece of flashing that is bent into the slot, and then bent to overlap the piece of flashing below.

Conclusion.  Since chimney leaks often have multiple causes, it is usually necessary to use all of the solutions above to ensure a dry and sound chimney. This means coating or replacing the cap, installing a drip lip at the cap, pointing up the bad joints, replacing the bad bricks, and adding new counter flashing. We have developed this holistic approach over the past twenty five years to achieve a complete, lasting, and visually pleasing remedy.

Photos and drawings of the solutions above are available below. (Click images for larger view)

Their
way

                                   
Click images for larger view
 
The unsightly "tin cap" fix.                      Tin cap with bad brick patch job.


                                                 
Click images for larger view                                      Typical failed, leaking chimney cap.
Typical used brick chimney with decaying
salmon bricks, cracked mortar joints. 


Typical unsuccessful attempt to repair flashing leak.
Click image for larger view


Our
way
(detail)
    Chimney       
Click images for larger view
 
New cap, drip edge, pointing, and counter flashing.  Click here for detail.
Please note new mortar color matches old.

In future articles, I will discuss the other general type of chimney as well as flue caps and heatilators.

    Robert Fina


Questions and comments are welcome at 703-718-0804 or email us for more information.

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