Posts Tagged historic masonry

Preservation – Looking Back to Look Forward – Workmanship of the Mason

US Treasury Department Building under construction, ca. 1867 - Image courtesy of the Library of Congress, Washington DC

US Treasury Department Building under construction, ca. 1867 – Image courtesy of the Library of Congress, Washington DC

I encourage the next generation of future masons to always look for opportunities to embrace mentors in our trade. And to the older masons I say make a difference in the world of a young person looking for a trade and openly share your professional experience in masonry knowledge in the preservation of important historic architecture. We each bring to the table a skill set that can, and will, make a difference – if, or course, we are given the chance and awarded the projects we seek to secure.

Many of you may not know about my background and experience in masonry preservation – so I will provide you with just a brief overview of how I ended up where I am today with the title of: “Historic Masonry Preservation Specialist”  I grew up in the masonry construction business working for my father, uncles, and grandfather in a family owned business located in Toledo, Ohio. This opportunity to be birthed into a family of working brick and stonemasons was not by choice but to keep me out of trouble in my teenage years.  And yes, it did work. There is something about carrying brick and stone, building scaffolding, mixing mortar, and cleaning out the toolbox that keeps one honest. I think I was just to tired after working all day to have the energy to get into trouble as I learned the trade of masonry construction is most demanding on the body.

As it turns out I developed a lower back injury that kept me from working in the trade actively – so I decided to go back to school and study architecture. It was in college that I began to appreciate the art of design and the process of construction as it related to historic and traditional masonry architecture. If I could no longer lift and set the stone – I could learn about how to preserve its original condition – and more importantly to do this in the means and methods of the original builders. This meant I needed to be willing to learn about traditional masonry construction tools, methods and materials. It also meant I needed to find other masons that understood these aspects of my new desire. The year was 1990 – 26 years ago. I researched my own family of origin in the masonry trade which dates back to 1870 in Posen, Prussia. So I was the 5th generation in my family to be involved in the masonry business.  The problem; however, was that the oldest living relative that would had known about traditional masonry construction methods, workmanship, and materials was my great grandfather and he died in 1951. My grandfather died in 1979; my father in 1985.

As luck would have it I secured a job at a lime manufacturing company in 1991. It was during my employment I discovered an enthusiasm for historic mortar materials, which of course are based upon lime, and have been for thousands of years.  Working with several conservators, architects, and a masonry contractor based in Toronto, Canada I began offering lime putty for use as a binder (without Portland cement) combined with sand at the jobsite. It was not long after; however, that I realized the need to train masons on the jobsite to use the Portland-free mix design and assist them in delivering the best quality possible. I traveled to England, Ireland, and Scotland over the next several years to work alongside other masons who generously mentored me in preserving historic masonry using lime mortars and traditional methods on castles. Then I brought that information back to the United States to assist in our training efforts here. That was 1998.

Lime Mortar Training Workshop at the U.S. Capitol, Washington, DC 1997. Image Courtesy of the NPS.

Lime Mortar Training Workshop at the U.S. Capitol, Washington, DC 1997. Image Courtesy of the NPS.

We made mistakes; we learned from our mistakes, we improved our methods, tools, equipment and materials. We did not give up. Encouraged from my mentor masons in Europe and Canada – I completed one project after another across the United States monitoring the progress as I went along. Writing, speaking and communicating with industry professionals I stayed focused. I wish to gratefully thank the pioneers in the masonry preservation movement in Europe that encouraged and personnally helped me like; R.H. Bennett, MBE, Winchester, England; Dr. Gerard Lynch, London, England; Mr. Douglas Johnston, Glasgow, Scotland; Mr. Patrick McAfee, Dublin, Ireland; Ms. Pat Gibbons; Charleston Fife, Scotland; the late Mr. John Ashurst, London, England; Mr. John Fidler, York, England; Mr. Colin Burns, Manchester, England; Mr. Stafford Holmes, London, England; Mr. Tim Meek, Charleston Fife, Scotland; Mr. Michael Wingate, England; Mr. Sam Trigila, Toronto, Ontario, Canada; Scottish Lime Centre; and English Heritage and the Society of the Protection of Ancient Buildings (SPAB) in London, England.

Since the early 90s I have been privileged to assist in the effort to establish (or best said, re-introduce) the lost art of true traditional masonry preservation with the use of lime mortars leading the way. As we continue this effort in 2016 we will actively be searching for architects and historic building owners that seek to preserve the architectural history and character of their properties by supporting the masons by offering onsite historic masonry training that is project specific. I strongly believe that by understanding our past and acknowledging the workmanship, trade practices, techniques, and tools used by the original masons in the process of the original construction we will have a better chance at success in the authentic preservation of historic masonry.

If we go into historic masonry preservation projects expecting that masons today should know all the details that are vital to the success of a masonry preservation project – I think we are asking for too much – especially in a low-bid environment in which many design professionals must deliver their services.  Let us expect the best, write excellent specifications to support quality assurance – but we must be realistic in the understanding of what that actually means to the mason working at the site. In many cases these men and women have never worked with a straight pure lime mortar before so there is a natural learning curve that must be acknowledged. But we can not, and should not, let masonry contractors figure it out on the jobsite without proper guidence. This is why I started my company to do just that – mentor and help the masons through training. The same way I learned in Europe.

Speweik Preservation Consultants are not masonry contractors. We use our hands-on historic masonry experience to provide the necessary technical consulting services in: condition assessment, material testing, specification assistance and masonry contractor training at the project site. We strive to support the efforts of the Architects and Historic Building Owners in meeting the US Department of the Interior’s Secretary Standards for Rehabilitation in Division 4 and to protect the historic integrity of the architecture under repair consideration.

, , , , , , , ,

2 Comments

Repointing – Joint Preparation

After a careful evaluation and clear understanding of why the mortar joints have deteriorated (or not, in the case of removing hard portland cement mortars) it’s time to repoint the wall. First, is the question of how deep to cut the old mortar out from the joints in preparation to receive the new replacement mortar. The Preservation Brief 2 “Repointing Mortar Joints in Historic Masonry Buildings 1998 published by the U.S. Department of the Interior’s National Park Service , Heritage Preservation Services gives us a good place to start.

Measuring mortar joint removal depth from the face of the wall

Old mortar should be removed to a minimum depth of 2 to 2-1/2 times the width of the joint to ensure an adequate bond and to prevent mortar “popouts”. For most brick joints, this will require removal of the mortar to a depth of approximately 1/2 to 1 inch; for stone masonry with wide joints, mortar may need to be removed to a depth of several inches. Any loose or disintegrated mortar beyond this minimum depth also should be removed”(page 9).

I like that the Brief advises on a range of mortar depths in correlation with the width of the joints.  It makes sense to approach the removal in this way.  Often I see contractors bidding repointing projects calling for the depth of the removal at ¾ inch. For most mortar joints that are the thickness of your little finger, about 3/8 inch, this is not deep enough. It does not cost the contractor any more money to remove another 1/4 inch of material during preparation and it makes for a better job.

Luckily for the projects requiring the removal of hard portland cement mortars from old historic lime mortar walls, the contractors of years past, did not follow this quality protocol of 2 to 2-1/2 times, otherwise the portland cement mortars would be much more difficult to remove. Instead, we most often find these projects only skim coated with the harder material. It is important as a mason contractor to know what you are getting into prior to bidding a project that has been pointed in portland cement. Questions you should be asking are; How deep is the non-original portland pointing?,… How hard is the mortar?,… and how difficult will it be to remove it without causing damage to the surrounding masonry units? Sometimes the only way to really know for sure about the answers to these questions is to commission a test panel prior to bid.

Thin diamond blade - turbo type (top)

A four-step approach to removing mortar joints in historic masonry buildings has been the industry method and best practice approach now for the past 15 years or so. First, the use of thin diamond-blade (turbo-type) grinders has been successful in cutting down the center of the horizontal (bed) joints for the removal of hard portland cement mortars. Second, followed by hand hammer and chisels or pneumatic chisels, to remove the excess mortar from the top and bottom of the masonry units. The vertical (head) joints are removed by chisel and hammer once the bed joints are removed. The third step is to use a caulking cutter with a diamond sickle type blade to clean the top and bottom of the masonry units and create a square cut back to the original lime mortar.

In the fourth and final step, mortar debris from the process should be removed by compressed air or a vacuum system. We do not use large amounts of water to flush out the debris during the cooler fall or spring months as it takes a long time for the walls to dry out especially the north facing elevations that do not benefit from the direct sunlight. We have unintentionally had efflorescence become an issue on some projects – waking up salts that lie deep within the masonry wall system due to excess water flushing.

, , , , , , , ,

Leave a comment

Moisture – Part Four, Solutions

Part of the solution to the problem of moisture migration is allowing the water to have its way. In above grade walls, that means letting it go through the wall, then redirecting it through flashing and weep holes if possible, and most importantly, using a breathable mortar that is more porous than the brick or stone.

Below grade, keep water from resting on the outside of the foundation walls in saturated soil conditions. Create a drainage system, a way for the water to move away from the foundation, perhaps installing perforated foundation tile at the base footing of the wall with gravel fill. Again, check gutters and downspouts to ensure they are clean and take water away from the wall, extending downspouts at least three feet past the elbow at grade level is a good idea. Grade the soil and pavement materials around the building to encourage water runoff and avoid collecting and pooling near walls.

A digital moisture meter in use

Detecting trouble in advance – The use of a moisture meter can sometimes be helpful in determining a baseline for acceptable moisture content in a historic masonry walls. Because not all masonry walls are created or built equally, all have varying levels of moisture depending on conditions. What is important in establishing a baseline is looking for the wall sections that are performing well.  In these areas, take readings to compare to areas with deteriorating brick or stone. This will put you on a specific path toward understanding what to expect in the future.

Also consider choosing breathable mortar materials like lime putty or hydraulic lime blended with coarse aggregate particles – often the vary material that has turned to dust over the past 100 years. Do not try to make it stronger or better. Just match the old lime mortar and move onto the next project. If the original historic mortar has turned into dust or is falling out of the wall, it is likely a lime mortar. It has done the hard work of absorbing more water than the brick over and over again and now needs replacement. The brick or stone is generally preserved in these cases.

The new lime mortar replacement mixture should match the old mortar and perform as the old mortar did – it to will turn to dust and fall out of the wall in the next hundred years, giving the next generation something to fix.

Lime Putty Suppliers in the US:

U.S. Heritage Group, Inc.

Virginia Lime Works

Hydraulic Lime Suppliers in the US:

Limeworks.us

U.S. Heritage Group, Inc.

Virginia Lime Works

, , , , , , , , ,

2 Comments

Moisture – Part Two, Capillary Suction

As promised from yesterdays post we were going to take a look at how water enters a building. We know water can enter a building in many ways, through masonry walls, roofs, windows, and saturated soil surrounding the foundation just to name a few. There is also interior sources of water, such a condensation from cooking, cleaning, showering – generally occupying the home. However, this is not the whole story when it comes to historic masonry walls. What we don’t talk about much is the “embodied water,” the water that remains in the walls at all times. Old historic masonry walls are moist in the center, due to the porosity of the masonry units, the lime mortars, and the thickness of the wall – it’s just hard for them to dry out completely. They really never do completely dry out, especially if they are foundation walls. We must consider this condition and account for moisture already present within the wall, because if we don’t, we could unintentionally trap moisture even when the outside of the wall feels normal and dry.

Capillary suction of water at different widths

Load-bearing historic masonry walls (16 inches to 24 inches in thickness) are porous, capable of wicking large amounts of water great distances due to capillary suction. The smallest cracks and pores found in mortar, brick and stone can bring on water in a big way. The action of wicking is energized by the horsepower of smallness. The smaller the pores or cracks in the wall, the more powerful the draw of the wicking action. If you have given blood, you may recall the very small glass tube the nurse uses to take a droplet of blood from your fingertip with a seemingly invisible vacuum cleaner. The blood droplet instantly goes up the tube – effortlessly, capillary suction at work.

The horsepower of smallness regarding the capillary action of water should be cause for concern, because architects and contractors are often focused on repairing large cracks in buildings while leaving the small ones untreated. Don’t be deceived. The small cracks, even the hairline cracks, are where the suction power is. One way to slow down the power of capillary suction is to reduce the surface area of the material that comes in contact with the water source. For small hairline cracks, injecting dispersed hydrated lime (DHL) into the crack with a syringe will sometimes do the trick. Unlike epoxy or cement, DHL remains flexible after it cures and maintains good vapor transmission, allowing the wall to breathe while at the same time halting the water – pulling the plug on the vacuum of capillary suction.

Dispersed Hydrate Lime (DHL) is a product imported from Germany and has been used successfully on many historic masonry structures here in the United States for over 10 years. Information on the product can be obtained by contacting the U.S. Heritage Group based in Chicago. Other vender choices I’m sure are available, but this is the product we have specified and are most farmiliar with using.

SPC Training video on DHL injection: http://www.youtube.com/user/SpeweikPreservation?blend=4&ob=5#p/u/4/mlGm2XvEGF8

 

, , , , , , , ,

Leave a comment

Moisture – Part One, Watertight Envelope Theory

Stone decay from hard cement repointing - Historic Scotland

The new term on the streets used by industry consultants to describe the details of how a building takes on water and then (hopefully) sheds it is “water management.” The longevity of historic masonry walls relies heavily on how water is managed in and around them. I am personally not yet convinced we can control water. I can work to manage where it goes, and possibly how long it stays – by redirecting it, but in the end it goes where it wants, the easiest way. When you attempt to fight water it usually wins. The ways water impacts a building depends on how long it stays – which is directly correlated to its architectural design, geographic location, topography, soil, the water table, the type of brick, stone or mortar, and whether the building has recently been restored.

Sometimes the understanding of historic load-bearing masonry walls built with lime mortar materials is not established, or respected, prior to a restoration project being undertaken. While the joints may look like they are in need of repointing due to deterioration, it’s important to know why they deteriorated in the first place. The cause is most likely from water saturation – then freezing and thawing or extreme temperature variations. One of the challenges is understanding that a building can, and does, breathe though its mortar joints as well as its masonry units.

The shear thickness of most load-bearing masonry walls keep the water out. The original building materials made for quick evaporation of the water on the surface of the walls and kept the inside dry, but this breathability does takes its toll on old lime mortar joints and they need to be repointed in high moisture areas every 75 to 100 years or so. Problems start when an architect specifies a replacement mortar that is harder than the original (in an effort to make it last longer) than potentially traps moisture inside the wall system. The effort in the restoration repairs is totally focused on keeping water out from coming in through the exterior side of the wall. The problem is that old masonry walls contain a certain amount of moisture already and often do not perform very well with harder/stronger mortar joints surrounding them.

When the goal of the restoration project is to create a Watertight Envelope you’d better run the other way – fast.  “Watertight Envelope” and “Historic Load-bearing Masonry” should not be used in the same sentence. Keeping water on the outside would seem to be an honorable goal for any restoration project, but observing the current condition of some masonry buildings restored in the past 10 years tells us a much different story, a troubling one. Basically, the buildings subjected to this watertight-envelope theory are not doing very well.

Where waterproofing and harder cement-based mortars are applied we find decay patterns that are surprising – in just a decade after application. Instead of the mortar surfaces wearing, there is a new pattern of brick and stone decay. Strong osmotic and hydrostatic pressures build up in brick and stone that are subjected to these hard, strong, and water resistant materials.

Tomorrow we will discuss how water enters a building.

 

, , , , , , , , ,

Leave a comment

The Lime Revival

J. Speweik during on-site masonry inspection

As a young boy growing up in a family of stone masons mixing mortar was like brushing my teeth…I did it every day, at least during the summer months when school was out. Who would have thought that in the age of technology, speed and convenience that my great great grandfather’s 1846 mortar formulation would return. The trend seems to be one that is sweeping across Scandinavia, Europe and Canada as architects and heritage masons work together to preserve their country’s historic masonry properties built hundreds and often thousands of years ago.  They call it the “Lime Revival” It’s been 30 years for Sweden, 20 years for England, 10 years for Canada….its America’s turn now.

The oldest archaeological sites in the world are, of course, masonry. As early as 2450 B.C., masons began using lime and sand for mortar. Lime is made from limestone (calcium carbonate) which has been heated to temperatures exceeding 1,650F where the heat drives off the carbon dioxide and water turning the limestone into quicklime (calcium oxide). Traditionally this quicklime (sometimes called lump lime or hot lime) was delivered fresh to construction sites or made on-site in a temporary kiln just for the job. The quicklime was mixed with damp sand and stacked up into piles for slaking into a hydrate powder (calcium hydroxide) and run through a screen or the quicklime was combined with water in the ground, formed into a putty (also calcium hydroxide), and mixed with the sand at a later time depending on the project needs. Either way, the mixtures were left to mature or rest for a time before use, due to the expansion of the lime particles during slaking.

The lime was generally mixed with local sand in a ratio of 1 part lime putty to 3 parts sand by volume. Other ingredients like crushed brick, clay, lamp black, and natural cement were sometimes found in smaller quantities before 1870; however, the basic lime putty/quicklime sand mortar formulation has remained unchanged for centuries.

Portland cement was first manufactured in America in 1871, but did not become truly widespread until the 20th century. As late as 1883 there were only three portland manufacturing plants in the U.S. Up until the turn of the last century portland cement was considered an additive, or “minor ingredient” to help accelerate mortar set time. By the 1930s, most masons were using equal parts of portland cement and lime putty or quicklime. Thus, masonry structures built between 1871 and 1930 might be pure lime and sand mixes or a wide range of lime and portland combinations.

What we do know about lime, and the reason for its come-back, is its incredible performance characteristics, and versatility as a time-tested building material – and not just as a masonry mortar either, but also as paint, (limewash/whitewash) exterior stucco/render, and interior plaster as well. Lime, when properly combined with clean, sharp, well graded sand can perform for many centuries in masonry applications. Lime has the ability to handle water without trapping it within a wall structure. It is breathable, flexible, obtains high bond strength to masonry units, it is truly sustainable (less energy is required to heat a ton of lime as compared to a ton of cement) and it has autogenious healing capabilities, often referred to as “self-healing” where hairline cracks do develop over time water combines with the lime again to re-knit the cracks back together. Limes durability comes through a process of what’s called carbonation. Carbonation is a process by which lime turns back to limestone by reabsorbing the CO2 back from the atmosphere though wetting and drying cycles. You can say that the material interacts with nature on a daily basis.

Portland cement mortar "Cover-up"

As portland cement became more widely used many lime sand mortars were being “covered-up” during repair projects. Exterior masonry buildings suffered badly from hard portland cement mortars (1940s until today) which did not accommodate for movement or stresses within the wall systems, and as a result, many historic brick and stone units got damaged by this un-sacrificial material. When cracks did occur, in the portland cement mortars, water would migrate into the wall cavities and not be able to escape or evaporate back out as they once had done with the lime sand combination mortars.

But times are changing. We are seeing signs of the “Lime Revival” hitting the shores of the United States. Mortar manufacturing companies are now offering lime mixes now for restoration and a few specialty companies offer traditional lime putty, quicklime and imported hydraulic lime for sale.

Lime mortar materials, that I am currently aware of, are available from the following U.S. companies listed in alphabetical order for your convenience.  Be sure to ask questions about each of the company’s offerings, as they differ. Some still use portland cement in their lime mortars. It’s best to know what you need first – then go out and find a supplier that can meet that need.

Cathedral Stone Products

Edison Coatings

LimeWorks.us

SpecMix

Transmineral

U.S. Heritage Group

Virginia Lime Works

, , , , , , , , , , , ,

2 Comments

High Compressive Strength – Not a New Discussion

Testing masonry materials for durability and performance has been going on for some time. It is important to study and test materials prior to construction of an actual wall to prevent wasted material, time and labor. Some of the earliest recorded tests performed on masonry mortar ingredients were carried out by the U.S. Army Corps of Engineers in the construction of fortifications during the early part of the 19th century.

The durability of masonry buildings relied heavily upon the past performance of the actual structures and the master mason’s experience with the individual materials. Much of the heritage knowledge of making good mortar was passed down from generation to generation through the trades. Testing mortar ingredients historically involved the masons working with the architects in a team approach for common understanding. However, signs of change began to appear as early as the 1890s.

Uriah Cummings - 1898

Uriah Cummings writes in his book, “American Cements,” which was first published in 1898. “With their former teaching and experience on the one hand, and the testing machine on the other, the question was not long in doubt. The machine was victorious, and henceforth all judgment founded on experience was laid aside and they became blind believers in the tensile strain tests. What matter though they were continually befogged by the frequent, unreasonable, and capricious pranks of the machine, they had found a god, and were determined to worship it.  And so it came to be established as a fixed belief among engineers and architects that the best cement was the one which tested the highest, and the manufacturer had no alternative but to strive to make his product test as high as possible.”

Seems from the tone of Mr. Cummings writing that he knew the industry was going in the wrong direction toward high compression. Is it high compression that destroys historic masonry? Well indirectly it does. Most mortars that are very high in compressive strength are very low in vapor permeability. The ability a mortar has to capture and release water easily through evaporation. What tends to happen in a historic masonry wall is moisture infiltrates by various ways; rising damp, poor roof/parapet/flashing details; driving rain; capillary action through cracks among other ways. The water needs to escape from inside the walls through the mortar joints ideally keeping everything dry from the inside out. Hard, high strength mortar prevents water from escaping thus trapping it inside the wall potentially causing damage to the masonry units of brick and stone as well as terra cotta over the course of time. It’s always better to insist on a lower compressive strength lime mortar that readily breathes with the masonry allowing quick evaporation of water, and in addition, provides the natural flexibility needed for traditional load-bearing masonry walls to perform at their best.

, , , ,

1 Comment

Hot Rocks and Compressive Strength

Looking down into a rotary kiln - the limestone can be seen on the right

Ever wonder why portland cement gets so hard? Why it is so high in compressive strength? This blog post is a continuation from an earlier one from last week titled “Hot Rocks” which most people seemed to enjoy. Early lime kilns could operate only up to around 1600F — just hot enough to activate the clay, turn the limestone (calcium carbonate) to quicklime (calcium oxide) and combine them both to form belite (dicalcium oxide) to make hydraulic lime.

Joseph Aspdin (1824) had achieved a slightly higher temperature of around 2200F forming some liquid phase and combining the belite with the remaining quicklime to create alite (tricalcium silicate), the base compound for portland cement. The vertical shaft kilns could burn slightly hotter, but temperatures were mainly kept below the maximum heat achievable to limit the liquid phase and prevent the danger of a kiln blockage, a situation created when the molten mass of materials cooled within the kiln. Kiln blockage was something kiln operators historically and understandably feared; crawling down into a shaft kiln and chopping away with a hammer and chisel at a molten mass of material was to be avoided at all costs.

The rotary kiln, however, not only helped to overcome the kiln blockage challenge, but it also allowed the higher temperatures necessary to produce portland cement with a much higher compressive strength. Before the rotary kiln was invented (1889) most kilns were constructed vertically, loaded with alternating layers of limestone and fuel (wood and/or coal or both) until the materials reached the top. A fire was started at the base of the kiln and allowed to burn for a day or two depending on how large the kiln was. The entire kiln was cooled down another few days until the materials were discharged from the bottom. The process would start over again for the next batch, a very labor intensive process. The rotary kiln also allowed for continuous feeding of the kiln without the usual starting and stopping and could run 365 days per year without interruption in production.

So just how hard is portland cement? Well, in a paper presented at the American Lime Conference in Lynchburg, Virginia in March 2003, Paul Livesey of Castle Cement presented the following information about the answer to this question. When matching a “portland cement” mortar from the period between 1871 and 1920 then, we should not be confused by the terminology. Portland cement of 1871 was a different material from that of 1920 which, in turn, is totally different from portland cement today.

Portland cement products produced at the turn of the last century were fired at temperatures from 2300F to 2600F. In comparison manufacturers making portland cement in this century fire at temperatures ranging from 2800F to 3000F. The differences in mineralogy and the effect that burning at higher temperatures has on strength development are well known. For example, in 1871, portland cement tested in the 1800 psi range; today’s portland cement are in the range of 8,000 psi, an increase of 344 percent in compressive strength. Indeed, the portland cement of 1871 bears more relation to modern, higher-strength hydraulic lime (NHL 5, 1000 to 1500 psi) than it does to modern portland cement.

And when making decisions on the appropriate mortar match for historic buildings remember that the National Park Service as well as leading American experts agree that it is always better to err on the side of a lower strength mortar replacement in order to protect the historic masonry materials. Even adding a small amount of modern portland cement can have a significant affect of increasing strength when maybe you did not intend to in the first place.

, , , , , , ,

3 Comments

Measuring and Mixing Historic Mortar

Various Sands for Comparision / Matching Historic Mortar

The traditional volume mix design of 1 part lime putty to 3 parts sand may be insidious to follow straight up without more details. First, mix designs historically used quicklime as the 1 part of lime mixed to the 3 parts of sand by volume. Quicklime when it is slaked with water will increase volumetrically 70-100 percent – or basically double its size. This fact would reduce the sand content closer to that of a 1 part lime to 1.5 parts sand – a much sticker richer mix design.

Secondly, sand must be measured in a damp loose condition according to ASTM C270 when mixing mortar. Dried sand will bulk up to 30 percent and grow volumetrically by the addition of a small amount of water. This can send your mortar mix designs at the construction site off the specified requirements.

I recommend everyone take a moment to read Gerard Lynch’s article on the subject it is well done. http://www.buildingconservation.com/articles/mythmix/mythmix.htm

, , , , ,

1 Comment

Qualified Masons…. On-site Training

Preparing for a Stone Dutchman Repair during a ASTM E2659-09 Historic Masonry Training at North Hall, ca. 1851 – University of Wisconsin, Madison

Most specifications call for masons to have five (5) years in historic masonry restoration experience in a similar project and scope of work. The problem is most mason contractors don’t often have the experience in the particular specification materials or methods of approach to specific projects. A new movement in recent years has been to assist the masons in gaining the necessary knowledge through on-site contractor training programs. These programs are specifically designed for the masons and teach them the workmanship skills required for specific masonry restoration treatments that may not be commonplace. For example, a crew may learn the techniques of Dispersed Lime Injection (DHL) or the installation and curing of lime putty mortar for repointing.

Architects and building owners are encouraged to attend these sessions. While they do not receive a certificate for the application, they do receive a supervisory role certificate in order to participate in quality assurance inspections during the construction phase.

The training is built from the framework provided in ASTM Designation E2659-09e1 Standard Practice for Certificate Programs. Each training event is carried out at the project site with the masons performing the work. The training programs allow owners and architects to identify qualified masons based upon delivering an acceptable test panel of each specified treatment. Each mason must meet certain criteria and pass a written test defined in the training program plan in order to receive an E2659-09e1 project certificate. An oversight committee is formed for each project representing the primary stakeholders. The primary stakeholders are typically the owner, architect and the preservation officer.

The project training program plan is developed by SPC personnel in collaboration with the project architect during the design development stage. The SPC training program dovetails into the project specifications and supports the quality assurance of the overall project. The project training program plan is submitted to the oversight committee for review and approval. The SPC certificate issuer is a qualified historic masonry specialist having designated authority charged to administer the training. The oversight committee typically requires that all masons and supervisors participate in a series of learning events designed to assist him or her in achieving the learning outcomes within a defined scope prior to working on the project.

Specifying SPC ASTM E2659-09e1 Project Certificate Training helps to ensure delivery of the highest quality craftsmanship and maximum life-cycle performance of the repairs.  All learning events in each training component comply with project specification requirements. The SPC training programs preserve the historic integrity of projects by assuring quality applications and installations of specified materials.

Because we work on National Landmark Buildings all SPC training components and learning events comply with all federal, state, and local building code requirements and preservation guidelines set forth in the Secretary of the Interior’s Standards for Rehabilitation.

To view training in progress visit: SPC ASTM E2659-09 Historic Stone Masonry Training – Remove, Redress, and Return Stone

To receive a copy of a template specification that includes training write to:  jspeweik@speweikpreservation.com

, , , , ,

Leave a comment

%d bloggers like this: