Using Natural Hydraulic Lime in cold weather, FAQ Friday with Randy Ruth

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As fall encroaches upon us with its cold weather, a question that is going to be popping up with more frequency is… Is it too cold to start or finish my project with NHL?

This may be one of the most difficult questions to answer, where the wrong answer can result in a lot of lost time and damage. The simple and safest answer is, do not perform work with NHL when temperatures will fall below 40 degrees Fahrenheit (including wind chill) for at minimum 7 days after placement of the mortar. Even following this model answer can result in frost damage of the mortar in some cases. So what is an applicator to do, to ensure that their work will last a reasonable amount of time? Well, care, caution, attention to detail, and patience is the answer.

If you can wait until spring to complete the project then you probably should to play it safe. If however, you absolutely need to complete the project before winter and do not mind playing with fire, then tenting and heating the scaffolding is an option. Tenting and heating can cost a lot of extra money in labor and fuel, so obviously make sure that there is enough money budgeted aside to warrant this approach.

By completely encasing the scaffolding envelope with heavy-duty plastic and being sure to affix the uppermost part of the plastic to either the roof or its eve, one can create a tight enclosed space for heating. When using a heater make sure that it is in a safe place and slightly raised off the ground. You should refer to any local building codes to make sure that you are in compliance and most importantly safe.

Of course, good masonry practices should not be skipped over just because the work is tented in and heated. Damp curing with burlap is still recommended and when repointing work is being executed good compaction of the mortar against the background mortar is still a must.

There are a few other tricks available to the applicator that can help prevent frost damage. One is the use of air-entrainment in the mortar. Careful dosing of an air-entrainer can help but not eliminate frost damage due to improper curing practices. Adding air-entrainment must be done with caution, as too much air in a mix will make the mortar weak and friable. When using proprietary admixtures, proper testing should be conducted to make sure that there are no adverse side effects .

Lowering the water content of the mix and increasing mixing time will help reduce the amount of water available to freeze without sacrificing too much workability. The use of warm mixing water, preheated sand as well as preheating the masonry units will help slow the development of frost. Winter accelerators associated with working with Portland cement mixes should not be used, such as calcium chloride or any nitrates. Depending on the properties of the surrounding masonry units NHL 5 can be appropriate to use in a masonry mortar to help withstand frost, due to its faster setting time.

When in doubt about working in possibly freezing conditions or allowing recently completed work to be exposed to freezing temperatures, you should probably trust your gut and call it a season. Dancing with the weather can be costly and should be avoided.

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Wet Basements and Masonry… FAQ Friday with Randy Ruth

Basements are notorious for moisture problems. Mold can spread quickly and cause serious health problems throughout a home. Here is another frequently asked question from Randy Ruth about basement moisture and masonry.

Q: I am having moisture issues in my old stone farmhouse, especially in the basement and I’ve noticed a few places where mold appears to be growing. I was told it could be because of the masonry but I don’t understand how that’s possible?

A: It should be noted that most old stone farm buildings were primarily build with lime mortar, especially before 1900. The source of for the lime used during its construction would have been local and probably made in a kiln on the side of a hill, by an experienced lime burner. What all this means is that the mortar between the stones would most likely be soft, with an affinity for water and have relatively good vapor exchange. Those characteristics are quite the opposite when compared to today’s Portland Cement based mortars.

Moisture from old stone walls can occur on the inside a building and can predominantly be evident in the basement. Accompanying the moisture can be mold, which can result in a decrease in indoor air quality and overall health. Such a problem should be addressed accurately and swiftly to minimize health risks. In order to identify an approach to this problem more information needs to be gathered and thought about.

Was there any recent work done to the exterior of the building?

Sometime when a non-breathing sealer or cement render is applied to the exterior of an old breathing building, natural moisture inside the wall can become trapped. When moisture becomes trapped inside of a wall it will travel to the point of least resistance. Often times this is the interior of a wall resulting in excess moisture accumulating on the wall. The excess moisture, typically above 20% can create a breeding ground for bacteria so long as there is a food source.

If paper faced drywall was installed on the interior of the building accompanied by such exterior work, then the moisture can not only deteriorate the gypsum in the drywall but also give the bacteria a food source. The bacteria resulting mold on the surface can consume the paper face of the drywall.

Has the landscaping around the exterior of the building been changed?

Down spouting and improper detail to appropriate grading can also be a culprit in moisture ingress. If water is pooling in areas and not being carried away from the building appropriately, excess water can penetrate the stone wall to the point where it is noticeable and cause mold problems.

The point here is that something has probably changed in or around the building in recent years to allow excess water in the building. There are many different remedies for water ingress for historic buildings, all of which have some merit and may be appropriate depending on the specific issue. However, complete and proper excitation of a good remedy is always crucial to success for any project.

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Burning Lime, The Traditional Way

This is an incredible video that really shows the difficulties of burning limestone the old way. Stacking wood, limestone and coal in an old kiln these men go through the process using traditional methods to turn regular limestone into caustic burnt lime.

Uploaded on Nov 27, 2010

This is from the Edwardian Farm series – how to make 10 tons of lime mortar in a massive kiln using layers of limestone and coal burnt for days!

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“Deteriorating Brownstones – FAQ by Randy Ruth”

by Randy Ruth

Q: I have an old brownstone house and some of the stone have been falling off, what can I do to prevent further damage and fix the damage that has already occurred?

A:  When you have brownstone deterioration or any form of stone deterioration and want it to stop, you have to first identify the root cause. Sometimes it’s as simple as replacing downspouts or replacing roof flashing, to prevent further damage to the stone. Other times it can be a long complicated series of tests and empirical analysis. Depending on the cause of the deterioration of the brownstone, a number of solutions can be applied.

If the stone is only sugaring or sanding with light deterioration, then perhaps doing nothing for a maybe a year and watching the stone for further deterioration is sufficient. However, if the stone is in much worse shape with possibly a ¼ inch or more of stone loss, then some could be some very serious problems with the integrity of the stone.

Brownstone as with many different types of sandstone has bedding planes. These bedding planes in the stone tend to detach from one and other depending on how the stone was laid in the wall. Imagine a layered cake as the stone, with each layer on top of one and other. If the stone cake is put on its side there is a greater chance that moisture can get between the layers and cause delimitation and or exfoliation. This being a common problem associated with sandstone, a more detailed resource for classifying the type of stone loss you may have can be found here.

It is always recommended that when fixing damage to stone that a qualified professional be brought out to see what the damage is and come up with an appropriate course of action. There are many different ways to approach fixing a stone like whether consolidation is appropriate is an appropriate first step or not. In my eyes, it is always best to honor the original detail of the stone and artisan who created it by only fixing what is broken. When patching stonework an important approach is to make sure that appropriate sympathetic patching materials are used. (Lithomex) The use of impermeable materials can cause further deterioration of the stone by trapping moisture. This will result in a faulty patch that can accelerate deterioration to the adjacent stone.

Brownstone with Water damage

Brownstone Before

 Brownstone Repaired with Lithomex

Brownstone After

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One quick question on Natural Hydraulic Lime, FAQ Friday with Randy Ruth

Fall has arrived, this morning it was in the 40s! Randy has quick answer today in his FAQ entry…

  • Q: Does your Ecologic mortar product contain just sand and lime pre-mixed (what are the major contents) with no cement and all I would need to do is to add water
  • A: Ecologic™ Mortar is a blend of 1 part Natural Hydraulic Lime 3.5 with 2.5 parts sand meting ASTM C-144 and iron oxide pigments when appropriate in our 9 stock colors. When you want to begin repointing the stone mortar joints after proper preparation of the wall, all you do is add water to the powdered contents of the bag in either a 5-gallon pail or mortar mixer and mix for about 10 minutes, then get to work.

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Techniques for Plastering a Wall, FAQ Friday with Randy Ruth

Q: I have painted drywall in my home and would like a lime plaster finish. How can I achieve this?

A: There are many ways to achieve a lime plaster finish over painted drywall. The first issue to address is who is going to do the work? If you hire a good plasterer then they should know how to approach this issue. Even still, you could enlighten them with new products that they may not know about, that you have discovered in your research. If you are a more “do it yourself” kind of person with some trowel experience than you might be surprised what kinds of finishes you can achieve with a little bit of practice on some 12″ x 12″ sample boards.

How you ultimately approach, this task is dependent on three major factors… budget, authenticity, and texture. Depending on the budget allocated toward a lime plaster finish, a person can achieve a wide range of finishes. The polished mirror finishes often-associated Venetian plaster can but not always be associated with higher costs. This is due typically to higher materials cost and higher wage costs because of the skills required to achieve that level of finish. Speaking of wage costs it should be noted that ceiling applications are much more labor intensive, rightfully so and should probably left to a professional plasterer. A rougher coarser finish can hide slight imperfections in artisanship, thus it typically costs less than other finishes. Since we have now linked the relationship between budget and texture to how you can achieve a lime plaster finish over drywall, it is time to move on to authenticity.

Authenticity refers to the quality of the product. Is it lime, acrylic, or a blend? Sometimes authenticity does not matter however; with the ever-increasing customer demand for low or no VOC products, it may play a role in your decision-making. There are flexible “lime” plasters that have chemical additions as well as many acrylic based bonding agents available on the market. If you want a more real lime plaster system on your painted drywall, than LimeWorks.us has a solution for you.

You should begin with a clean sound surface, free of any soaps or detergents and of course with no peeling or flaking paint. A quality finish is only as good as the quality of what is beneath it. Then simply trowel apply Takcoat™ evenly over the entire wall 1/16th to 1/8th inch thick. This will act as a transition coat from paint to plaster. Takcoat™ uses hydraulic lime and natural additives to achieve a bond that can stick to glass, ensuring a good bond to the painted wall. Once the transition coat of Takcoat™ has cured for a about 3 days, a second coat of lime can be applied to achieve the finish. Depending on the what the kind of finish is desired another coat of lime can be applied, or even three, four or five. It all depends on what you or the client wants.

If a rough finish or soft-sanded finish is desired than Ecologic™ Mortar in either coarse or fine sand can be applied. If a fine polished, finish is desired than NHL 2 can be applied paper-thin in multiple coats to create depth to the finish, which is polished with black soap diluted with water. all of the products mentioned can be blended together to make the right finish for you or the client. Custom colors can be matched for you, or you can add your own iron oxide or natural lime proof pigments.

Because of all the case specific challenges, answers to this FAQ are just a basic overview. If you plan to tackle this issue head on, give a call or shoot an email to info@LimeWorks.us. We can help you with choosing the proper products and application techniques.

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A Message from Ian Cramb, a younger man…

We got an email back in 2011 with some amazing photos of Ian Cramb. These photos are from 1958 in Iona, Scotland. Ian was working on the cloisters of Iona Abbey at the time. Iona is a small island off  the west coast of Scotland near Oban. These photos came from another Ian, Ian Taylor who spent a month living in Iona as a student in 1958 where he captured these photos during his stay on the island.

Also, in the recording below Ian talks about the apron he is wearing in the photo. He only wore that apron during his time in Iona and every morning it was blessed before he began the day’s work at the Abbey.

ian-cramb001 ian-cramb-iona

Get Ian Cramb’s book here: The Stonemason’s Gospel

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Differences Between Repointing with Natural Hydraulic Lime (NHL) Mortars vs. Cement Based Mortars FAQ with Randy Ruth

Q: Is pointing with lime different from pointing with cement? I’ve done work with cement but I want to know what the differences are for application and general use for repointing my old house. Can you help?

A: When you refer to pointing, I am thinking you are referring to repointing mortar joints. As with any masonry project, proper attention to preparation of the substrate is critical. Always follow proper preparation guidelines regardless of the mortar being used.

If you compare the application process of repointing mortar joints with lime-based mortars to cement based mortars, the only real difference is workability.

Lime mortars tend to have better workability than their cement counterparts do. This is because lime is used to add plasticity to modern cement mortars and thus, when you omit the cement you have the greatest workability. However not all lime mortars can be treated equally when it comes to their aftercare during the initial curing process. Like cement-based mortars, there are different grades of lime for different applications, with different characteristics.

Although there are many different types of limes used around the world, I will only address the four most common from softest and slowest setting to hardest and quickest setting. starting with High calcium lime putty, (Natural Hydraulic Limes) NHL 2, NHL 3.5 and NHL 5.

High calcium lime putty is the softest and slowest setting of the lime choices. Proper attention to curing procedures must be adhered to allow it to set properly, this may take six weeks. Lime putty based mortar has its place in the world, where trained professionals should be the applicators to ensure work is executed in way were the margin for error is limited.

Different grades of Natural Hydraulic Lime are followed by a number designation that indicates the minimum compressive strength at 28 days with a particular amount of sand in Newton’s per millimeter squared. The reason for this classification is that there are no Natural Hydraulic Limes currently produced in the United States and must be imported from where the metric system is used and there have been established standard for a number of years on NHL’s, primarily in Europe. As said before, the lower the number designation for NHL’s the slower setting and softer that type is. So, what does all this mean to you the mason or adventurous DIY homeowner?

Well if you have a conservator mindset then matching the new mortar as closely as possible to the old mortar in color, texture and physical attributes is the end goal. You might want to consult a professional for general advice on what type of mortar to use if you are unsure, after conducting your own research. In general, for most of the United States NHL 3.5 mixed with local sharp well graded sand, which should meet ASTM C-144 or a pre-blended NHL 3.5 and sand mix can be used for general repointing work of older brick and stone structures. This is because NHL 3.5 has an acceptable initial setting time and more importantly provides good vapor transfer in a wall. This allows repointing work to move along at an acceptable speed while knowing that in most cases moisture is not being trapped in the wall cavity. Lastly, the difference between cement mortar and lime mortars for repointing is aftercare. Even though cement based mortar should be damp cured it is not always practiced and is not typically the same length of time when dealing with lime. While working with NHL mortars it is important to allow the mortar to slow cure with high humidity or by misting with water, keeping the recently completed work damp. Although the length of time for aftercare curing of mortar will vary in direct proportion to the particular grade of lime used. Generally, 2-4 days of slow damp curing with either damp burlap misting for repointing work is acceptable. In some cases however, this curing period should be extended.

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FAQ Friday with Randy Ruth

Hooray, Today is Friday! Another rainy weekend will be upon us here in Pennsylvania, but now it’s time for another FAQ Friday with Randy Ruth. Today’s question is another very common question on the use of lime mortars vs. cement. After you finish reading please visit our new facebook page and “Like” us…

  • Q: Could I perhaps use cement and sand? What is the advantage of using lime on old stone structures
  • A: You should not use only cement and sand for a variety of reasons, the first being that in today’s mortars, lime adds workability and plasticity to the Portland cement mortars. Without lime in the mix or proprietary additives, the cement and sand mortar will have extremely poor workability. Secondly, modern-day cement is much different than early cement or lime, it is very hard, dense, vapor impermeable, and brittle. Cement can trap moisture inside the wall and erode the mortar behind the repair mortar, this can cause further unseen deterioration and masonry unit (stone, brick, terracotta) deterioration, thus resulting in a delayed and much larger/costly masonry repair.

The advantage of using an appropriate lime mortar on old stone structures deals with compatibility. There is a rule of thumb when approaching a restoration project and that is to repair in kind with like materials. By following this approach an individual can avoid unforeseen problems associated with trying something “new and improved” when there is such a well over 2,000 years of lime building history. There have been a number of studies done around the world on historic structures that conclude that even a small amount of Portland cement added to a lime mortar mix, can cause detrimental damage to the adjacent masonry and historic bedding mortar.

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Lime Mortars vs. Cement FAQ with Randy Ruth

Shall I use Lime or Cement?

Q: Could I perhaps use cement and sand? What is the advantage of using lime on old stone structures

A: You should not use only cement and sand for a variety of reasons, the first being that in today’s mortars, lime adds workability and plasticity to the Portland cement mortars. Without lime in the mix or proprietary additives, the cement and sand mortar will have extremely poor workability. Secondly, modern-day cement is much different than early cement or lime, it is very hard, dense, vapor impermeable, and brittle. Cement can trap moisture inside the wall and erode the mortar behind the repair mortar, this can cause further unseen deterioration and masonry unit (stone, brick, terracotta) deterioration, thus resulting in a delayed and much larger/costly masonry repair.

The advantage of using an appropriate lime mortar on old stone structures deals with compatibility. There is a rule of thumb when approaching a restoration project and that is to repair in kind with like materials. By following this approach an individual can avoid unforeseen problems associated with trying something “new and improved” when there is such a well over 2,000 years of lime building history. There have been a number of studies done around the world on historic structures that conclude that even a small amount of Portland cement added to a lime mortar mix, can cause detrimental damage to the adjacent masonry and historic bedding mortar.

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Phone: 215-536-6706

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