Spalled brick in an1860s lighthouse that was repointed with portland cement mortar about twenty years ago. The historic stone masonry units have deteriorated dramatically, while the portland cement mortar joints remain intact. It' s important to understand that historic buildings are very different than modern buildings in several key ways: First, historic brick--in particular--is softer than modern brick because modern brick is fired at a much higher temperature than was possible in the past.

Yes. As we have already mentioned on this page, historic brick was fired at a lower temperature and is typically softer than modern brick. Construction techniques have changed, but it's still important that the mortar accomodate the historic brick. Due to the prevalence of portland cement mortars (notably the standard Type N), very few masons have worked with traditional lime mortars.

Hydraulic lime mortar is a lime mortar that hardens in damp or even wet conditions through a chemical reaction rather than exposure to air. (This is in contrast to standard, or non-hydraulic lime mortars, which harden by absorbing carbon dioxide, a process known as carbonation.) Hydraulic qualities are created when clay is included in the lime mixture.

Obviously, you want to avoid the kind of damage described above, and in order to accurately recreate the original mortar you typically have to have the mortar analyzed. Although a building constructed before 1871 was undoubtedly pointed with lime mortar (because portland cement wasn't even available until that year) the years after 1871 are a grey area.

Lime mortar will not cure a problem caused by poor detailing on the property, such as undersized gutters, a lack of a roof overhang, outside ground levels that are higher than floor levels or capped unventilated chimney stacks. They will however allow walls to dry out after problems such as this have built up high damp levels within walls and they will allow the wall to be able to breathe again.

The colour and texture of a sand has a considerable impact on the appearance of the finished mortar. The fine aggregate particles give a lime mortar its colouring; the larger fragments give its texture. Most lime binders are white, light grey or cream in colour, and therefore the colour reproduction of the sand is excellent, compared to OPC mortars. We can carry out analysis of original mortars and isolate and grade the original aggregates used to help with matching.

These are mixes of lime putty and coarse sand, used for building, pointing, rendering and plastering. The mix for mortar is normally 3 or 3.5 parts sand to one part lime putty by volume.

We supply our premixed lime mortars in sealed dumpy bags or sealed tubs. It will last indefinitely as long as long as air cannot get in to carbonate the lime. This means keeping it from drying out and storing it free from frost. Mortars with hair teased in will gradually lose the hair as it dissolves in an alkaline wet mortar and you will end up with an unhaired mortar. Mortar left for many months will take more "knocking up" to plasticise the lime mortar.

Animal hair, usually horse, cow or goat, is added to the backing coats of lime mortar used for external rendering or internal plastering onto stone, cob, brick or timber lath. Adding hair gives extra strength and minimises shrinking and cracking. It allows thicker coats to be applied to uneven walls and holds the plaster keys in place when plastering onto lath.

Both lime putty and lime mortar should be protected from frost. If frosting should occur, it is possible to reuse frozen lime mortar so long as it is completely thawed out and thoroughly mixed before use.

Lime is calcium oxide applied in granular form. Lime helps improve lawn color and density, controls thatch, and increases root development. Lime balances the pH levels in the soil that have been affected by the fertilizer applications throughout the year. To read more about the importance of Lime, please read our Article entitled "Winter Care."

With a growing emphasis on the need to reduce energy consumption and reduce CO2 emissions there is an argument for the use of traditional limes. The production of many natural hydraulic limes offers a significant reduction in energy, compared to that required to produce Portland cements.

Fat lime mortars require construction to take place at a slower rate but hydraulic limes cure quickly enough to allow building work to proceed quickly and do not delay work even on the largest construction sites.

Either. Pelletized is easier to apply but powder is cheaper. Use powder if you intend to incorporate. There is no difference in speed of reaction.

Buildings, neighborhoods, and landscapes are often thought of as being historic solely because they are old. Does that mean that all old places should be protected and preserved? The decision to protect historic places rests in the meaning they bring to our lives as places that define and mark our history. For example, a building may be historic because it was designed by a well- known architect or was the first county courthouse or is the place where a significant event occurred.

RIHPHC does not produce signs for historic buildings. Contact your local preservation or historical society, or email Jeffrey Emidy or call him at (401)222-4132 for a list of sign makers.

First, identify who is requiring approval and under what rules. Typically, this is the local Historic District Commission if your neighborhood is governed by historic district zoning. Call your local planning department or building official. If you are applying for an RIHPHC incentive (tax credits, loans, etc.), you will need RIHPHC approval.