Historical masonry buildings are very different from modern buildings.  Historical bricks were fired at lower temperatures and are much softer and more permeable than modern bricks and buildings constructed with these softer bricks were designed to absorb moisture and then release it.  A key component of this design was the lime mortar historically used in masonry applications, a mortar that was also soft and readily allowed water or vapor to pass through it.

In the late 1800’s, a new mortar debuted in the United States at the height of the Industrial Revolution.  Favored for all the qualities a mass-production revolution could ask for (fast-curing, inexpensive, and less work for masons), Portland cement quickly gained popularity with masons and by the early 1900’s most buildings had some Portland mortar in their masonry surfaces – usually as an additive to traditional lime mortar.  By the mid-1900’s  Portland was no longer used as an additive and became the predominate ingredient in mortar mixes.  Historical buildings were not immune to the new technology and masonry repairs on historical buildings in the 1900’s were predominantly made with Portland mortar.

If your historic building has been re-pointed it likely was with Portland mortar.  A common mistake, Portland mortar applied to historical buildings doesn’t just erode the historic fabric of the building, it causes physical damage that is often permanent.  Traditional mortars worked with the softer historical masonry materials to expand and contract together as temperatures and moisture levels changed, creating a wall and masonry surface that “breathed” to expel excess moisture.  Applying a Portland mortar mix to historical masonry disrupts that relationship and traps moisture in the wall and historical bricks.  Moisture trapped within the walls will not easily pass through Portland cement mortar and will be forced through the soft brick instead, the path of least resistance.  When the water evaporates, salt deposits are left behind that crystallize and destroy the protective shell of the bricks.  Once this outer surface is damaged, the softer interior of the historical bricks rapidly disintegrates.

Portland mortar can cause problems that begin to decay masonry in a few years.  The historical bricks on masonry buildings are not the only things threatened by Portland cement mortar – structural elements, interior features, and occupant health are also compromised by the moisture issues associated with Portland mortar.

Remember, historical masonry materials and mortars were designed from a construction approach that created buildings that “breathed”, allowing moisture both in and out.  Modern masonry materials and mortars are designed from a watertight construction approach that aims to keep water from passing through.

Combining a material from the system designed to let a house “breathe” with a material from a system designed to prevent water from passing through is a recipe for disaster.

The truth is…historical mortar differs significantly at a molecular level from modern mortar.  This difference makes modern mortar incompatible with historical masonry materials, permanently damaging historical masonry materials, and structural elements of masonry buildings, and traps moisture in walls lowering energy efficiency and endangering air quality inside the building.

Protect Historic Masonry Buildings from Permanent Damage Caused by Portland Mortar

Historic masonry buildings are very different from modern buildings.  Historic bricks were fired at lower temperatures and are much softer and more permeable than modern bricks.  Historic buildings constructed with these softer bricks were designed to absorb moisture and then release it.  A key component of this design was the lime mortar historically used in masonry applications, a mortar that was also soft and readily allowed moisture to pass through.

In the late 1800’s, a new mortar debuted in the U.S. at the height of the Industrial Revolution.  Favored for all the qualities a mass-production revolution could ask for (fast-curing, inexpensive, and less work for masons), Portland quickly gained popularity with masons and by the early 1900’s most buildings had some Portland mortar in their masonry surfaces – usually as an additive to traditional lime mortar.  By the mid-1900’s Portland was no longer used as an additive and became the predominant ingredient in mortar mixes. Historic buildings were not immune to the new technology and masonry repairs on historic buildings in the 1900’s were predominantly made with Portland mortar.

If your historic building has been re-pointed in the last sixty years, it very likely was re-pointed with a Portland cement mortar mix.

A common mistake, Portland mortar applied to historic buildings doesn’t just erode the historic fabric of the building, it causes physical damage that is often permanent.  Traditional mortars worked with the softer historic masonry materials to expand and contract together as temperatures and moisture levels changed, creating a wall and masonry surface that “breathed” to expel excess moisture.  Applying a Portland mortar mix to a historic masonry surface disrupts that relationship and traps moisture in the wall and historic bricks.

Moisture trapped within walls will not easily pass through Portland cement mortar and will be forced through the soft brick instead, a path of much less resistance.  When the water evaporates, salt deposits are left behind that crystallize that destroys the protective shell of the bricks.  Once this outer surface is damaged, the softer insides of historic bricks rapidly disintegrate.

Moisture issues caused by Portland mortar on a historic building can begin to destroy historic masonry within just a few years.

The historic bricks on masonry buildings are not the only things threatened by Portland cement mortar – structural elements, interior features, and occupant health are also compromised by the moisture issues associated with Portland mortar.  Remember, historic

masonry materials and mortars were designed from a construction approach that created buildings that “breathed”, allowing moisture both in and out.  Modern masonry materials and mortars are designed from a watertight construction approach that aims to keep water from passing through.

Combining a material from the system designed to let a house “breathe” with a material from the system designed to prevent water from passing through is a recipe for disaster.

Historic mortar differs significantly at a molecular level from modern mortar.  This difference makes modern mortar incompatible with historic masonry materials, permanently damages historic masonry materials and structural elements of masonry buildings, and traps moisture in walls lowering energy efficiency and endangering air quality inside the building.

Here’s a tool you can use to evaluate your historic building’s masonry for potential problems and problem indicators. For a printer-friendly version of this checklist, click on the picture.

 

On Tuesday A. Tamasin Sterner from Pure Energy Coach spoke on the topic of indoor air quality at the monthly breakfast meeting for the Central Pennsylvania Preservation Society (CPPS).  
A single hour in Tamasin’s presence, is easily one of the most informative hours you’ll ever experience in your life and Tuesday was no exception.  The Historic Restorations family and other attendees at the meeting learned what the single most important aspect of energy efficiency and healthy air in a home is:
Balancing the air that goes out with fresh air coming in to achieve a neutral pressure field. 

Energy expert Tamasin Sterner shares her knowledge of Indoor Air Quality

It turns out, balance and moderation are not just good for your waistline and stress levels, it’s good for the air in your buildings too. Tamasin taught us how to evaluate and balance the air flow in buildings and the kinds of things that impact air flow patterns.  Not only does balanced air flow maximize energy efficiency, it protects the health of the building’s occupants and users, and preserves the materials and structure of the building.  
We were particularly interested to learn about the many ways air flow balance in a home is disturbed with all the seemingly innocuous improvements and changes we make to buildings that aren’t things we would have connected to impacting energy efficiency.  
Did you know that recessed lights placed near an air return can make you sick?  That sealing off the roof in your house can create moisture issues?  That even the appliances in your kitchen can create an imbalance in the health of the air of your house?  Did you know that many times asthma and allergy issues are directly related to the health of the air at home?  Did you know that sealing a house is really only half of the picture of energy efficiency?  Do you know what the other half is?  
It’s ventilation.  Without proper ventilation, insulating a house well is actually a bad thing.  It will decrease your energy efficiency, lower the quality of the air you breathe, and set up prime conditions for developing moisture issues.
Tamasin gave us those tidbits and tons of other information in her presentation, but perhaps the most surprising information from the presentation was

There is one single, simple, FREE, thing that all HVAC installers should be doing (but aren’t!) to check for proper drafting and ventilation when a new system is installed in a house and how to ask for it to make sure it gets done.  

When 30% of houses have high levels of carbon monoxide, 80% of houses have gas leaks, and the most common cause of older and historic building deterioration is uncontrolled moisture, this is critical information to have.  

Balancing the air in our buildings can not only contribute to energy conservation, it will keep our buildings healthy so the humans that use them stay healthy in order to continue expanding our healthy and living historical preservation.  
Healthy buildings.  Healthy Humans.  Healthy Histories.

If you haven’t yet attended a monthly breakfast meeting for CPPS, or you don’t make it a habit to attend regularly, you should.  Meetings are only $15, include a continental breakfast spread (with The Cork Factory Hotel’s homemade pastries), and expert presenters that cover a variety of topics.  You can see their upcoming schedule and register to attend one of their monthly breakfast meetings at: centralpennsylvaniapreservationsociety.org/events.


The November/December 2009 issue of Preservation Magazine featured an article, Getting Ready for Winter: 15 Steps to Efficiency. These tips are taken from this article.
  • Insulate the attic (this is where the majority of your heat loss will occur – though the replacement window and door companies would have you believe it is on the walls of the house – heat rises.)
  • Zoned heating system (heat only the areas of the house you “live” in).
  • Bleed radiators and clean forced-air vents.
  • Have your furnace serviced.
  • Change your furnace filters once a month.
  • Install a programmable thermostat (turn the heat down at night when you are in bed and during the day when you are away).
  • Insulate duct work and hot water pipes in cool spaces. Install foam inserts behind electrical receptacles and light switches (they sale the inserts (with precut holes) for behind the covers at any hardware store).
  • Close fireplace dampers (when the fireplace is not in use – we have had a call from someone not sure why their house was filling with smoke).
  • Set ceiling fans to low and switch direction so the hot air is being forced downward from the ceiling.
  • Make sure bathroom fans have functioning dampers.
  • Keep your original windows maintained (caulk, fix glazing, replace broken panes, repair wooden parts, and install weather stripping).
  • Install storm windows.
  • Use lined curtains, working shutters, and insulated window shades.
  • Caulk holes at exterior penetrations (mail chutes, etc.) only use exterior-grade caulking for this job.
Green building is all the rage in the building industry. I can not open a remodeling or design/build magazine without a reference to a green building project. Preservation and restoration work is green in it’s approach. By using resources (building materials) that have already be harvested on land that has already be cleared is a greener approach than building a brand new building using new green materials. When you are building a new building you have to create the resources, ship them to the building supply store, and then ship them to the job site on the newly cleared land (from farmland, forest, or a tear down).

Storm Cunningham in The Restoration Economy (covering all aspects of the restoration economy natural and built environments) states that 25% of all landfill waste is from construction activities. By reusing the salvaged materials from buildings that are being torn down in our restoration projects we are keeping those materials out of the landfills.

It is easy with these new green materials to refer to new building as green. The new building materials are green for a new building approach but that approach is not necessary the best method when working on an older home (one built before 1945). There are ways to take a green building approach when dealing with your older building that does not include retrofitting inappropriate modern materials.