Repointing brick or stone is not as simple as it sounds. Masonry repair work can not only damage but destroy old homes, unless you are an informed consumer and know what to ask. You the homeowner are responsible for protecting your home.
Repointing brick or stone on OLD HOMES performed by most professional masons, or homeowners instructed by brick manufacturers on repointing brick, will result in the destruction of your house!
Read on – this is extremely important. Let the buyer beware!
Most of the best and well known masons out there may do a great job building a NEW brick wall, but you should use extreme caution when hiring them if you own an old home. When working with new brick, there is no problem, only the old brick and here’s why.
This pertains to homes build in the early 1900’s and earlier. Modern brick is fired differently and is therefore harder.
Your home may have wood shingles, but don’t forget about chimneys and foundation walls constructed with brick or stone. As time passes, the masonry on old homes eventually needs repair. The mortar holding the bricks or stone deteriorates. Cracks then form, allowing water to enter. If neglected, the freeze and thaw cycle will cause the bricks or stone to fall out and hit you on the head.
What do you do to prevent this? Repoint the mortar.
Repointing brick or stone is a process where about 1 inch of mortar is removed and replaced with new mortar. This is a very common practice and all masons do this. The problem lies in their knowledge of what type of mortar to use. Using the wrong type will cause irreversible damage.
Mortar used today is very strong and hard because it contains a large amount of Portland Cement. Portland Cement is good for certain applications, but it is not a fix-all as masons and building supply stores believe. Portland cement is not bad, it just must be used in the mortar mixture in a lower percentage when working with certain materials.
1. The important thing to know is the mortar MUST be softer (in compression strength) than the brick or stone it surrounds and have greater vapor permeability.
2. It must also be softer than the mortar it is replacing when repointing brick or stone. This is accomplished by using less Portland Cement and more Lime and Sand.
Moisture within a wall needs to escape and evaporate. Mortar that is too hard will force the moisture to escape through the softer brick or stone. This will result in permanent damage such as cracking and spalling.
This is a photo of damage caused to bricks from using the wrong type of mortar. The same problem occurs with stone.
Mortar Types for repointing brick and stone.
What you need to know:
Mortar comes is types. Type M, S, N, O, K, and L.
Type M is the strongest and hardest and contains the highest percentage of Portland Cement while Type L has no Portland Cement and is the softest.
Type O and Type K are recommended for most historic masonry applications. However, masons are not aware of this. When hiring a mason, ask them what type they would recommend and see what they say – that is the test. Play dumb at first.
Forget about Home Depot type stores. I wanted to ask the pros in the concrete, block, and sand business that specialize in masonry work.
I recently contacted Clayton Concrete Block & Sand (www.claytonco.com ) a very large company in NJ, and told them I had 150 year old brick that needed repointing. They recommended Type S. I played dumb and asked if it may be too hard for the old brick and asked if they carry Type O or K. I was told they are not familiar with those types!!!
I then phoned a different office and Type N was recommended and again this sales person was not aware of the softer mortar types. If I depended on the pro’s in the business for information, and repointed my basement foundation, 10 years later I may not have a foundation. Let the Buyer Beware!
The words of an honest mason
The following was posted in a LinkedIn forum discussion:
How do we make all Masons aware that using Portland cement is ruining our historical Masonry! This is as big of a problem as one can possibly be.
We see all these historical society groups raising Hell about all different types of issues but nothing is said about the masons who go out into our cities everyday and open up a bag of Portland Mortar and start packing joints and ruining work that is over 100 years old. The question is how do we educate the Masons who don’t know anything about Restoration Masonry but call themselves Restoration Masons?
“I consider myself to be a Great Mason and I have 28 years of laying Brick and just up to 3 weeks ago i had no idea about the damage that i could do to historical Masonry if I used Mortar that we use today on masonry that was done before 1933. If I would not be the type of person that reads up and researches things before i do something’ I could have done the same as all the Masons I see do and been using Portland Mortar also.
THANK GOD FOR THIS SITE IT SAVED ME FROM POSSIBLY RUINING A PIECE OF HISTORY.”
I would love to take the credit but the site he references is the LinkedIn forum.
Lime versus Portland Cement – The Craftsman Blog by Scott Sidler
See what to do based on the age of your house.
For much more detailed information and a chart of types of mortar to use for different applications go to:
Unfortunately their customer service is not very good. I have asked the owner a question and have not been responded to.
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