Masonry Magazine June 2004 Page. 20
Restoration Techniques
It is interesting to note that "hiding immediately behind what seems to have been a misunderstood nomenclature was a lost art.
The Recipe for a Proper Repointing Job
All recipes require ingredients. For the repointing of older structures, the ingredients consist of:
1) The Mix. Over a century ago, mortar had a different composition than the mortar used in modern masonry. In the past, mortar was produced from limestones that were fired at a high temperature, turned to powder, and then water and sand were added. It was called a lime putty mortar or a traditional lime-based mortar. Logistical problems, such as slow setting and lengthy preparation, led to the search for an easier product. One thing led to another, and Portland cement, which was invented and patented in England in the 19th century, eventually became the main mortar ingredient, making the traditional lime-based mortar obsolete for new construction.
As a general rule, if the building was constructed prior to 1872, it should be repaired with a traditional lime-based mortar consisting only of lime and sand, as well as some color pigment. If the building was built between 1873 and 1932, it should be repaired with a mortar that consists of lime, some Portland cement and sand, as well as some color pigment. This is still considered a traditional lime-based mortar. If the structure was built after 1930, it can be repaired with a modern cement-based mortar, although I personally find that some buildings built up to about 1945 are best repaired with a mix consisting of Portland, lime and sand.
2) The Sand. Don't assume that the sand you always use will do! Have a look at the sand used on the building you will be restoring and see if you can get a type of sand in your area that will, at least approximately, match it.
HISTORIC MASONRY RESTORATION CONFERENCE
The International Masonry Institute, the City of Annapolis, Md., and the Maryland Historical Trust are teaming up in presenting the first in an annual series of Historic Masonry Restoration Conferences. The events will be headquartered at the Historic Inns of Annapolis, conveniently located in the heart of historic downtown Annapolis, August 26-28, 2004.
A designated National Historic Landmark, Annapolis has more original 18th century architecture still standing than any other city in the United States.
Also, recent statistics show that over half of all new construction contracts are for restoration or adaptive re-use, comprising roughly 17% of the masonry dollar.
Restoring America's architectural treasures requires specialized knowledge and skills. This conference will focus on historic mortars, with a three-track education session including mortar analysis, mortar basics and a walking tour of historic Annapolis, Seminars will provide invaluable information on materials' properties, historic mortar analysis, lime putty and mortars, sand and aggregates, diagnostics, specifications and much more, Other sessions will include the national sand library, a case study restoration, hands-on laboratory sessions in pointing and cleaning, panel discussions, and a final program on condition assessment.
Registration for the event is $300 per person, and accommodations at the Historic Inn of Annapolis are available on a first come, first serve basis for $149 per night. Classroom and hotel space is limited to 200 participants, so reserve your space now!
For more information, contact Dawn Lafey at dlafey@imiweb.org or call (410) 280-1304.
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18 Masonry
June 2004
03-20
www.masoncontractors.org