Restoration of the Eldridge Street Synagogue in New York City with Ecologic® Mortar

In the heart of what is now Chinatown on the Lower East Side in Manhattan lives the Eldridge Street Synagogue. A very important Jewish Synagogue built in the late 1800s, it was the first synagogue to be built by the Eastern European Jews emigrating from Russia, Romania and Poland. The synagogue flourished for its first 50 years and was revered for its gorgeous vaulted ceilings and stained glass windows. But the membership began to dwindle following the great depression and was abandoned in the 1950s. Harsh city life ate away at the building, it became home to flocks of pigeons and other critters. Leaks developed and the stairs became unstable, the remaining members retreated to the basement where they remained for almost half a century.

The rescue effort of the Eldridge Street Synagogue began in the late 70s when volunteers and the Friends of the Eldridge Street Synagogue initiated efforts that led to an $18.5 million dollar repair campaign. This campaign included repointing work of the facade using Ecologic® Mortar from LimeWorks.us Additional repairs to the ceiling, wallpaper, paint and almost every aspect of the central room was restored returning it to its original glory. The final element was set during the fall of 2010, the stained-glass window commissioned by Kiki Smith and Deborah Gans is the only 21st century element inside the historic space.

More details of the Eldridge Street Synagogue restoration can be found in the latest issue of Traditional Building Magazine

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

Facade after restoration, photo credit: Kate Milford

All Photos Copyright Sean K Maxwell

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

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 maybe one 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.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

Happy Birthday Randy Ruth, and FAQ Friday!

Send Randy some love and give him a birthday shout out when you repost his latest blog entry on some of the differences between repointing with Natural Hydraulic Lime (NHL) mortars vs. cement based mortars.

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?

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.