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Should my brick building be completely repointed?
The process we recommend in the proper maintenance of exterior brickwork is to do as little intervention as possible in regard to the pointing mortar if in fact the large majority is still intact. We replace only what is missing wholly, or eroded back more than 3/8", with fresh mortar, which will match very closely to the original mortar in composition, color and texture. The total repoint of a building is often unwarranted. Patch pointing is cost conservative as well as functionally superior than pointing the whole building in an incorrect manner. If total repointing is to be done because the majority of the mortar is past its useful service life, a mortar should never be applied that consists of a portland cement and fine sand paste placed over the top of the existing joint. This technique employed by many "restoration" masons is superficial because of a shallow depth which lacks a good mechanical key to the surrounding brickwork and over time may delaminate. However the biggest disservice that this technique brings is that the fine portland cement, which will pass through a sieve that water itself will not pass through, will allow the wetting and drying cycles of the building, which is the eventual cause of masonry failure, to occur through the brick thus exacerbating its breakdown. The "wicking-in" of water through the brick, which can then can be driven further into the building by blowing rainwater, may cause interior damage.
Correct total repoint requires removing the joint to a depth of approximately 2-1/2 times its width and then using a compatible mortar in relation to the final p.s.i. and water-vapor transmission rate as that of the remaining joint and brick. High lime content pointing mortar is compatible with the soft and absorptive nature of historic brick which rely on their "fired skin" to protect themselves and the building from rain intrusion. If high portland cement content pointing mortar was used instead of lime, when moisture in the brick were to expand and contract during freeze/thaw cycles, often the unyielding mortar forces the softer face of the brick to exfoliate thus leaving a vulnerable unburned "salmon" center of the brick exposed to the elements.
Should I have the brick building "sealed" upon completion of patch pointing or full repointing operations?
The use of "sealers" on exterior historic masonry is a questionable intervention. Since all historic masonry walls and the individual units need to "breathe", (i.e. allow vapor to escape), there should be a specific purpose. Only after physical waterproofing via pointing and physical repair should chemical "waterproofing" be considered. Those considered must have properties which have a high vapor transmission rate which will allow moisture to escape. The specific purposes to use a water repellent are:
1. Inhibiting deterioration of the masonry units by not allowing the wetting/drying cycles, (the very cause of historic masonry failure over time), to occur through the unit or the joints. Although repellents are not traditional historic material, they can act as a sacrificial barrier to weather elements which was once performed by the fired skin of the brick which has eroded and now exposes the soft salmon orange, non-vitrified center for an accelerated breakdown.
2. As a grain strengthener, (surface consolidant/water repellent).
3. As an inhibitor to capillary action and the absorption of water into the building if the absorption of the brick is greater than the masonry's ability to release the water back into the atmosphere before entering the building's interior.
My bricks on the chimney in the attic are disintegrating, have a white powder on them and look like they need to be replaced, what causes this?
If there is moisture present at the gable end of a brick or stone building and the roof system is working and the flashing system is working around any chimney's that extend past the roof line, the moisture may be due to condensation. A column of air that exists, in used or unused and capped-off tight chimneys, moves the expanded air through a natural draw upward and the moisture content in the air may be condensed by change in pressure, (dew point), or thermal shock, (at the line where the air in the chimney goes through the roof). All masonry, wood and building materials have an "r" value which means restriction to airflow. So a cap that seals a chimney does restrict airflow but does not eliminate it. It takes approximately 11 inches of masonry to equal the "r" value in 1 inch of wood to demonstrate approximate value differential. Air which tries to move up and out but condenses near the top gets quickly absorbed into an unlined and capillary filled chimney. The plaster and lime bedding mortar or soft salmon brick are what is highly absorptive.
The moisture problem is exacerbated when a high efficiency gas or oil heating system pumps out an exhaust, into an uncapped/unlined chimney, that is practically nothing but hot air full of moisture and some unburned impurities. Even in the case of a lined chimney, the liner should be insulated on the outside of the liner within the walls of the chimney. The "salmon" center of the brick exfoliates on to the floor in the attic as salt crystals, (efflorescence), build up under the "fired skin" of the brick and jack out the face of the brick and jack out the continual reoccurring "salt skins" thus hollowing the bricks out. The moisture wants to move toward the inner, warmer attic instead of the colder outside conditions. Unused chimneys should be filled with free flowing vermiculite masonry fill insulation and capped off at the top. Liners should be cast-in-place lightweight concrete which is creosote/acids resistant and insulative, or stainless steel, which unfortunately may deteriorate in time by acids in creosote, with an insulative blanket or vermiculite placed around the liner. The stainless option is less expensive at the front-end of installation. The poured-in-place type is an excellent long-term value if installed properly.
I Have other "damp" walls on my historic brick or stone buiding, what could that be from?
Moisture that is seen in the masonry walls at first and second floor level when it has been determined that no plumbing is leaking within the wall, or improper pointing, flashing or cracks are apparent on the outside, may be due to various causes.
1. "rising damp" from the earth graded toward the building instead of shedding it away, or drainage up against the building that does not let the water be shed away but carries it to the surface of an absorptive wall below grade. This is apparent when plaster crumbles near the baseboard of the first floor or above the baseboard heating unit since the heat pulls the air toward itself. Dig down along that side of the house and after a parge coat (1:1:6), apply a bituminous foundation coat to seal out moisture. Next grade the earth or remove loose fill that causes drainage and re-grade with less percolating soil that allows water to be shed-off.
2. There are unused flues built directly into the thickness of solid brick or stone walls that need to be filled with vermiculite or if used, properly lined.
3. The moisture content in the room or an adjoining room/ basement is great and requires proper ventilation. Often rooms in older houses are tightened up with thermal windows and further power-cooled and equally should be power-ventilated and not rely on ridge, soffit, or unbalanced venting methods. Especially when north-east driving rains push against an already super-saturated wall the result is often water infiltration into the building's rooms....see water repellent notes if applicable.
This guy wants to sandblast my house....should I let him?
Invasive cleaning methods such as sandblasting or high pressure washing should be a questionable intervention upon historic fabric of any kind and should be considered carefully. Quartzite sand should never be the medium used on historic brick whose frail "fired skin" will be destroyed and thus expose a porous "salmon" center and never used upon other stone with intricate carving or glazing that can be irreversibly removed. Other media is available such as ground up walnut shells, baking soda, diatomaceous clays, glass beads and are judged on their effectiveness by how non-invasively they work upon the historic substrate while lifting only the undesirable contaminant. One could employ quartzite sand, (in varying gradation and at various p.s.i. pressure), when there is a sacrificial element allowance and need for aggressive cutting is desired such as in the case of tenaciously adhered portland cement staining from poor repointing or cementicious whitewashes when the substrate is common fieldstone with no intricate carving, or not historic brick. Modern brick will lack a porous "salmon" center having been thoroughly burned in a tunnel kiln but will become "pitted" by sharp sand action. However if any case where the limitations are realized and anticipated beforehand still warrant the use of sand as the medium this method is at your disposal if a test sample proves it is effective and the desired result is achieved while always maintaining an eye on conservation of historic fabric. Be sure of this fact : surface area of masonry exposed to the elements is increased once sandblasted and micro-cracks may be introduced by violently aggressive sandblasting especially by inexperienced operators. Another draw back in the use of this already unpopular method is that silica dust will be produced and this is the reason why the introduction of water as a knockdown to dust. When the sand comes out of the orifice, and is pulverized into dust upon impact, the water greatly reduces dust. A vacuum blaster is used when one must collect all of the contaminant such as paint. Some municipalities do not allow sandblasting of any kind because of the negligence and misuse of the tool and because of the irreversible damage caused to historic structures. This truly is a good idea on their part since more damage is done than good over all. Should you let him sandblast? Most probably not.
Why in the Sam Hill are beautiful stone farmhouses and other historic stone buildings covered with stucco in the first place ? My mother told me it was for insulation. However, the house is freezing. I got paint peeling off the stucco. I want to take the stucco off and point the stone to stop air infiltration and make the house look good.
So, are you supposed to take it off or will this de-value its historic appropriateness?
Traditionally the only exposed stone is one with a gauged mortar joint. "Free stonework" are irregular pieces but shaped to fit with large, squared alternating corner stones as borders. Ashlar work is varying sizes of cut blocks of stone that are laid in uniform coursing.
Fieldstones are stones picked up off the field when settling a property and preparing the ground for farming. They are laid up in "rubble work." Some masons pronounce it "roobil" work. I think they are just repeating the accent of the old-timers. Rubble is junk. Fieldstone is just junk stone, not dressed up in any way. "Roobil" sounds rare and costly... so you might as well call it that too because it’ll cost you dearly to restore...if you don't use our efficient work crews!!! The traditional mortar of choice before 1932, when *Corson's of Plymouth Meeting, PA, the oldest pre-hydrated and bagged building lime company invented the automatic hydrator and married a bag of portland cement to a bag of hydrated lime, was simply to mix slaked lump lime on the jobsite with aggregates of various types, (usually stream bed sand, dirt and clay for a bedding mortar). The pointing mortar was usually the same lime but with sand only and at a 1:2 RATIO. The exterior plaster may have also had animal hair in it to improve the binding.
But the question remains, Why did they cover the stone with exterior plaster? Well, when you don’t gauge the joints and keep them tight the surface exposure to the elements exacerbates erosion of the pointing mortar and may quickly deteriorated the bedding mortar and the integrity of the wall or at least aid in the transmission of water in to the building. So, the same soft, punky mortar that was used for bedding was also used for exterior plaster and finished off with a shelter coat that was the pure calcium carbonate limewater “whitewash” that was used as a waterproofer and protecting coat. It was like putting an eggshell coating on the otherwise frail render. Today the appearance of rubblework exposed is thought of as a thing of beauty. Then it was a more squared and formal wall with straight, true and gauged joinery as the sign of high-end work. Really, it still is. If buildings where not plastered but only received the inverted “v” joint to deflect the downward and angled drive of the rain, they where also whitewashed right over top of the stone and joint as a shelter coat. When you don’t see the whitewash over the stone anymore it is because the acidity of a constant rainwater bath has loosened it and it has come off and was not renewed. More often than not it remains under the porch of houses and forebay areas of barns where it has been protected.
The only insulation
gained by exterior plaster is that of slowing a driving wind. Overall masonry
is a poor insulator. 1940 and newer stucco with perlite incorporated in the
mix adds insulation. To correctly restore something would mean to put it back
to its original design. Therefore for correct architectural restoration the
plaster should remain and be finished as it was originally. However, with unsound
plaster which has lost its bond to the substrate, has cracks in it or paint
that is flaking and a total removal being considered, possibly just repointing
it may be an option. It is an option to help mitigate the water infiltration
problem, its an option for an eyesore problem of flaking paint, and an option
for getting value of what your return is on equity against what the cost is
that you expend. But “just say no” when you’ve got a mansard
roof, or other ornate Victorian elements, that’s all I ask. A repointed,
rustic look, should be reserved for a simple country farmhouse, outbuilding
or barn. As far as conservation of historic fabric and as the example of a type
of architectural detail found only on your building consult with your local
historic appropriateness review board or historical society to come to a conclusion
to point or not to point.....that was the question wasn’t it?
Is it acceptable re-pointing to paste a thin over-lay of mortar over the original concave profile of a mortar joint ?
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Surface pointing, (also known as a "scrub joint" ) is commonly applied as a pasted joint with little depth of material. It is in fact the most common method of "repointing" a whole building but contributes very little. In fact many times this method accelerates deterioration by trapping water in the wall with high concentrations of Portland cement in the mix used. Many "Restoration masons" utilize this method because pasting over the top of slightly recessed joints with a thin overlay goes up very quickly and gives the appearance of a lot of work received for what is a small amount of money charged for the work. In the end, the less savvy homeowner thinks that since the entire wall has been "repointed" the uniform look of all joints being filled is a complete job and they received a good value. |
The fineness of Portland cement and fine play sand made in a 1:1 ratio with little or no lime content is what makes this fine paste. The brittle, often gray Portland cement colored, scrub joint cracks and falls out within a few years.
Where it does not fall out and was filled into deeper voids it helps to keep moisture trapped in the bedding mortar and only allows any moisture in the wall to escape through the face of the masonry unit, if it were to get out at all. A resulting "picture frame" of proud gray mortar remains with hollowed back masonry units as the final irreversible damage. "Tuck pointing" is what some inappropriately call the scrub joint. The scrub joint is very similar to grouting the face of tile although the scrub joint is applied course by course on the brick joints. The actual root of the name "Tuck pointing" comes from a narrow keyway cut into the center of a molded brick joint and then filled or "tucked" with a bright white, red or black lime putty to give a more formal and gauged appearance to the brickwork.
Prior to the tucking in of this lime putty a red color wash is first applied to the bricks and mortar joints to give uniformity and aid as a shelter coat. Remnants of this color wash and infill of putty can be found on many historic brick buildings in the eastern states. The "grapevine joint" has taken the place for the name of a true ruled key and tucked joint and what is often reproduced in a restoration effort is simply the grapevine joint without the proper color wash and lime putty in-fill.
Do you travel to consult or perform work ?
We have been asked to consider doing consulting work or bid projects in Texas, Nevada, Illinois, Michigan, Puerto Rico, Virginia, West Virginia, New York, Delaware, New Hampshire, Vermont, New Orleans, Florida and many other states.
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Denbigh
Hall Condominiums, Wilmington Delaware
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Denbigh
Hall Condominiums, Wilmington Delaware
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Andy
deGruchy taking moisture meter readings.
We were hired to hunt down leaks in the large building and put together a plan to correct the root cause. |
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| A small luxury hotel located in Massachusetts where we prepared an intervention plan and put numbers together to carry out the plan we designed. |
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| This is the deLabra School in San Turce, Puerto Rico. The General contractor who won the project paid my way to visit the site and spend a few days reviewing specifications and preparing a masonry restoration bid. |
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