What is Masonry Repointing?

If your home or property is constructed from stone or brick and it was built more than 70 years old, you'll probably notice that the mortar between the joints is not as stable as it used to be.

Flaking, crumbling and long cracks in the mortar or brick are all indications that the structural integrity of the original mortar may be compromised. At the least, the aesthetic quality of the mortar should be reason enough to consider re-pointing.

At this juncture you should call in a qualified, professional mason. They will be able to tell you in detail what you need to do to restore the integrity back into the structure.

This will undoubtedly mean that you’ll need to have the mortar removed from the joints, up to an inch in depth, and then new mortar pushed back in to the joints. It's a fairly messy and dusty process to have the joints ground out, so your windows and doors should all be closed and preferably covered with plastic during this process. The washing down of the debris and the consequent re-pointing work is as clean as it gets in construction work, it's just time consuming and labor intensive.

Before contracting any mason, ask for details of other re-pointing projects they have been involved with and ask for photos if they have any. Any professional mason will be proud to show off their previous work.

Another point to consider is the use of the correct mortar for re-pointing. If your mason brings out a caulk gun to re-point your home’s masonry, stop them. Using incorrect strength mortar can cause your home more long term damage at the expense of short term aesthetics. If your property was built prior to the early 1900s, it's likely that the original mortar was made from lime or a natural cement. Taking a small sample of your mortar and having it analyzed for content will soon tell you if it's a lime-based mortar or not.

Most properties built using brick prior to the 1940s used soft clay bricks that were fired at lower temperatures than the modern brick of today. Using the wrong mortar here can severely damage that brick within five years of you having the re-pointing done.

If your mortar is lime based, then on no account should you allow the mason contractor to talk you into using a Portland cement mortar, which also known as Ordinary Portland Cement  or OPC. Within a very short period of time the cement pointing will fall out of the joints because of the chemical reaction between lime-based mortar and the cement-based mortar, as you can see from the photos. Water retention will also become prevalent if they do this. It’s an apples to apples comparison here folks. Lime mortars should be replaced with lime mortars and cement with cement of the correct strength.

A quick word about lime mortars: hydrated lime is used by masons to soften the cement based mortars and make it more workable. This should not be confused with natural hydraulic Lime (NHL), which is the closest thing to the old lime mortars that were used back in the Victorian era. Again, the new lime cements and mortars come in different strengths, so make sure the correct mix is being used.

A qualified mason knows this and will also be able to color-match your original mortar with the products available to date.

Don't take chances with your re-pointing: ensure your mason is properly qualified, licensed and insured to do the job correctly. Once re-pointed, the mortar should last at least another 50 to 70 years and your property will benefit both structurally and aesthetically.

Keith Boyd, the owner of Windsor Masonry in North Kingstown, Rhode Island, has over 40 years of experience in masonry and was trained traditionally in the United Kingdom after a 4-year apprenticeship. His specialties are in historic masonry restoration and the use of lime mortars.

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