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Here are a few of the questions from homeowners that we get on a regular basis.

Here are a few of the questions from homeowners that we get on a regular basis.

Nothing bothers me as a homeowner worse than seeing cracks in my brick joints and joints that have completely fallen out. I have to look at it day after day, and I am afraid that water, bugs and air is coming into my home through those joints.I have an old brick home. I would even call it an historic brick home. It was built sometime in the 1800’s, but I don’t know when. Somebody repointed some of these mortar joints at some point with some ugly, gray mortar that doesn’t match at all.Now I read that Portland Cement damages old historic brick homes. I want to get this Portland Cement mortar out, and put the right stuff in. The faces of my bricks are starting to crack and fall off. Is this what you call spalling?

How do I find out what is the right mortar for an historic brick home? I want some repointing done, but every mason that I talk to uses regular cement for the pointing. I need a company that will help me design the correct mortar for my historic home or building . I want to use something that more closely matches the original mortar for pointing. Is the lime mortar from Lancaster Lime Works compatible with the mortar in my building? Is your lime mortar going to match my mortar, and will it last a long time?

If these are the kind of questions you have regarding your old brick or stone home here in Lancaster Pa contact Lancaster Lime Works today.

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General Project Conditions for Using Lime Mortar

General Project Conditions for Using Lime Mortar

1. Bedding and lime pointing mortar should be placed only if air and masonry temperatures are between 40°F (4°C) and 80°F (27°C), and the air is relatively calm. Conditions must remain so for at least 48 hours after completion of work. If conditions are not within these parameters, Contractor shall take all necessary measures to ensure that the manufacturer recommended protection and curing requirements are met, including as necessary, dampening of burlap, polyethylene sheeting, wind barriers, and other protection as needed.

 

2. The wall must be thoroughly whetted down at least 24 hours before work is begun. The wall must again be whetted down at the beginning of the day then be monitored thru-out the day. If the wall drys out it will suck the moisture from the lime and the lime mortar will not reach it’s compressive strength.

 

3. Contractor must be aware that working conditions change thru the day. In the morning hours the temps will be cooler and the surface will not have direct sun. In the afternoon the mason must provide proper shade from direct sunlight or the lime will dry out to quickly. All masons on the project must constantly monitor the pre-wetting conditions and apply more water as needed to keep the wall at a proper moisture content.

 

4. Contractor shall not start work until joint faces and solid bedding have been prepared as approved.

 

5. Contractor shall not allow direct weather related water against mortar until it has reached its full cure.

These general guidelines for working with lime mortar are not complete and should only be used as a starting point. Using Lime Mortar requires extensive training. Contact Lancaster Lime Works for more information on how to use Lime Mortar and to purchase it.

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Brick and Mortar Basics

Brick and Mortar Basics

The following provides an overview of the characteristics of brick and mortar, and how they sustain unnecessary damage through improper maintenance. This is provided to assist in understanding the masonry sections of this report. A more thorough comparison of Portland mortar and hydraulic lime mortar will be found in some of our other blog posts.

 

Bricks that were used in the construction of the original older buildings were fired at lower temperatures than modern brick. They do have a hard exterior, but are still much more porous (absorbent to moisture) than modern bricks. If the harder face of the brick is removed by sandblasting, the much more porous and fragile interior of the brick is exposed to the weather. Sandblasting was widely accepted in the past as a way to clean dirty, painted, or stuccoed brick. It is now widely known to significantly weaken brick’s resistance to damage from weather.

 

The original brick and mortar building walls were laid with hydraulic lime mortar, which has been in use for around 7,500 years. It is made by burning limestone, and it gets hard by going through a chemical reaction with water. It is very different from the Portland cement mortars used over the last 100 years. Portland cement is much harder, less flexible, and is completely non-porous. Portland cement mortars are now known to threaten the longevity of brick and stone walls, and can greatly accelerate damage to soft brick.

Moisture from the weather, both humidity in the air and precipitation, penetrates bricks and stones in a wall because they are naturally porous. This moisture in the bricks can cause rapid damage to the bricks if it cannot escape quickly, especially in freezing weather. Hydraulic lime mortar allows moisture to escape very quickly out of a wall. Portland cement traps moisture in the wall. Moisture that is trapped in a brick wall causes the brick faces to break off, leaving a rough, ugly, fragile exterior. It also causes moisture problems on the interior, such as plaster decay, stains, and wood rot.

Brick and Mortar walls that are constructed of older, softer brick should be repointed with hydraulic lime mortar, never Portland cement. Walls that have been repointed with Portland-based mortar should be repointed with hydraulic lime mortar. Brick faces that have been severely deteriorated can either be repaired or replaced. Replacement of the bricks can be done by finding new bricks that match, or by removing and turning around the original bricks. Damaged bricks can be repaired by using Lithomex, a flexible, porous, lime-based material that is applied in lifts to the face of the damaged brick bringing it back to its original shape, size and color. It bonds with the damaged face of the brick, and becomes a permanent repair.

Old brick and mortar with damaged bricks can also be removed from the wall using special tools. Sometimes the damaged and spalling bricks can be removed, turned around and reinstalled. Others will be so badly deteriorated that they will need to be replaced entirely.

The method of removal for existing Portland-based mortar is extremely important. Using a grinder will create a lot of dust, and the spinning diamond blade very easily causes irreparable damage to the face of the old brick. We suggest using a power tool called Arbortech, along with a high quality vacuum system. It has two vibrating blades that act like scissors, cutting into the Portland-based mortar and greatly minimizing potential damage.

Contact Lancaster Lime Works

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How to Remove Mortar Before Repointing Brick

How to Remove Mortar Before Repointing Brick

The biggest challenge in restoring masonry walls and buildings is repointing brick, replacing Portland-cement-based mortars with a natural lime mortar. The difference between the two is easy to determine. Using a pointing chisel to remove lime mortar is quite easy; the mortar is soft and breaks easily in front of the chisel. Portland-based mortars are quite hard, and hand-chiseling takes many blows from the hammer to remove just a couple inches of joint. This hard mortar is very damaging for brick and soft stone.

 

One reason they are so damaging is that Portland-based mortars (Type N, Type S, and most mortars available today) are not water permeable, so they do not allow moisture to escape from the wall. Also, Portland-based mortar is not flexible, but brittle, so the masonry units are stressed by freezing temperatures and imperceptible building movements. This can take the faces of brick right off of buildings that should be preserved and protected. Natural lime mortar will wick moisture away, and flex with the small movements of temperature changes and settling that occurs in every building over time. Thus the need for brick repointing.

 

To remove Portland-based mortars efficiently, a grinder should be used to cut a groove in the center of the joint then repointing brick with the correct lime mortar can begin. Usually a thin blade works better than a thick one, and a 4″ blade will cut through the Portland-based pointing back to the original lime-based mortar. Cutting the center of the mortar joints prevents slip ups from damaging the original brick or stone. Special care should be taken on head (vertical) joints to cut only as deep as the grinder can without cutting into the masonry units. This can take strength and focused attention because the grinder is harder to control when removing very hard material. Center-cutting the joints relieves the pressure that the hard mortar puts on the faces of brick and stone.

 

When you’re repointing brick, the second step is to hand chisel the joints out. Usually the best method is to place a flat chisel right where the mortar meets the edge of the brick or stone, aiming toward the center groove that was cut with the grinder. A pointing chisel can also be used to go across. Pick a 2″or 3″ section of joint and aim the pointing chisel toward the area that has already been removed. The chisels will break the bond between the Portland-based mortar and the brick or stone.

 

In repointing brick usually the repointed joints are less than an inch deep, so removal is safe as long as care is taken with the faces of the masonry units. Remove mortar at least 2x the height of the joint. A 3/8″-wide joint should be chiseled back to at least 3/4″. This will ensure an adequate bond between the new brick mortar and the brick or stone.

 

Once the mortar is removed, the joints should be vacuumed, or blown out with compressed air. A low pressure jet of water, such as from a nozzle on a garden hose, can also be used. If the joints are vacuumed or blown out, it is a good idea to dampen the wall before applying the new mortar.

 

Never use a pressure washer on soft brick or stone. High-pressure water can damage walls of even hard stone (like granite), so the nozzle should be kept well back from the face of the stone. Pressure washers often remove the beauty of the weathered faces of stone, including the green moss that can make a building look old.

Contact Lancaster Lime Works Today