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Page 4
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| Jack under lintel. Wall is rebuilt on concrete footing. |
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Mortar (continued)
Here are a few examples of problems to consider:
1. Wooden sills rotting from sustained moisture. The Sills of old houses were typically resting, 16 to 20 inches above grade, high and dry upon a brick or stone foundation wall or upon split granite “set up” stones.
Now we see old houses that appear to have sunk into the ground with their bottom most clapboards at grade.
In the 19th century, it became fashionable to surround a house with a necklace of shrubs.
As the decades passed, the annual fallen and composted leaves caused gradual rise in the grade.
The house never sank, but it might as well have for now the sills lie beneath the snow.
The solution, after the sills have been repaired, is to remove the shrubbery and return to the original grade that must be pitched to drain away from the house.
2. Bulkhead collapses and lintel above drops, causing brick veneer face to split and sag.
Note second floor windows sagged out-of square. Examination shows that, with no drainage provided for gutters, water ran down the bulkhead wall, froze and pushed it out.
When we began this repair we had a surprise. All the settling problems were confined to the basement and the lower first story.
So, what caused those sagging second floor window casings? A drunken mason in 1825? That would be my guess.
When his brickwork came around the house, he was one course off. That’s about 2 3/4 inches. Hard to hide, but also hard to fix.
So somebody decided to leave the mistake. Just have the carpenters make crooked windows. Make them about 2-3/4 inches out of square. We decided not to correct this situation… it has been structurally sound for 150 or so years. |
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Detail showing original brick coursing “off ”
by one course. |
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3. House catches fire because chimney settling allows hot coal to work down through rubble masonry and ignite beam.
This little coal smoldered for a week on basement drafts, and finally lit up the beam and part of the house.
A solution for this hazard is to pour a hidden concrete slab to seal off the fireplace and hearth from wood.
Everything still looks original, even the crow’s mouth joints.
4. Original Chimney blown apart by Concrete flue liner. A poured concrete liner is a quick, relatively inexpensive and fireproof method for bringing an unlined chimney up to code. Or is it?
The hard and impervious liner is a change to a natural breathing system, a flowing system where water absorption was quickly evaporated by the warmer air in the chimney.
With the introduction of the concrete liner, water trapped between the bricks and the liner froze, and when it expanded the soft bricks rather than the hard liner blew apart.
To the cost of the liner add the cost of completely rebuilding the chimney and installing a proper terra cotta liner. In this case, the shortcut costs more.
5. Building Code requires the use of lab tested high temp refractory cement for setting flues.
Lab condition tests show this water soluble cement takes a hard, fireproof, durable set at about 400 degrees F.
Real life conditions: the house has five chimneys with nine fireplaces. The Owner only ever uses one fireplace.
The flues at the top of the chimney he does use are 42 feet away from fire, and the chimney is constantly chilled by raw New England winds.
Even with a hot fire, the heat doesn’t reach the uppermost flues at a temperature sufficient to harden the cement.
Result: Over a year or so, the rainwater washes away the majority of the refractory cement.
Solution: use RF cement to meet code and go over the outside of all joints with a heavy layer of regular mortar.
6. Lab tests determine fireplaces to be inefficient. Engineers recommend elimination of fireplaces.
Real life condition: Hundreds of clients over decades declare unanimous love for their fireplaces.
Solution: Determination of aggregate efficiency must include spiritual and aesthetic efficiency. |
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