Repointing historic masonry the right way - Part 2 - Pointing Mortar Joints

Summary

This video provides a detailed guide on applying historic lime mortars for masonry work. The mortar should have a consistency similar to brown sugar and be packed into joints by hand, ensuring no air voids. The process involves overpacking vertical joints, using a pointing iron to press the mortar into place, and scraping off excess mortar to achieve the desired joint profile. The joints should be thumbprint hard before finishing, and excess binder should be removed with a turn brush, exposing the aggregate. The video also highlights the differences in appearance between slicked-down and properly finished joints, particularly with colored mortars.

Takeaways

• 😀 Historic lime mortars should have the consistency of brown sugar.
• 😀 Mortar can be packed into a ball by hand and applied into horizontal joints.
• 😀 Ensure there are no air voids when packing the mortar into the joints.
• 😀 Mortar may be applied directly from a hawk for better efficiency.
• 😀 Vertical joints should be over-packed by 1/16 to 1/8 of an inch.
• 😀 Scrape the mortar onto the face of the pointing iron before pressing it into the joint.
• 😀 Wait until the mortar is 'thumbprint hard' before moving to the next step.
• 😀 Avoid slicking down the mortar joints; excess mortar should be scraped back to achieve the desired profile.
• 😀 Use a turn brush to remove excess binder, exposing the aggregate and the edge of the brick.
• 😀 Note the visual difference between slicked-down joints and properly finished joints, especially with colored mortars.

Q & A

What consistency should historic lime mortars have?

Historic lime mortars should have the consistency of brown sugar, which allows them to be easily packed into a ball by hand.

How should mortar be applied to the joints?

Mortar should be pushed into the horizontal joints by hand, ensuring that it is packed in a way that eliminates air voids.

How should joints be over-packed for vertical mortar joints?

For vertical joints, the mortar should be over-packed by 1/16 to 1/8 of an inch to ensure a solid fill.

What is the proper technique for applying mortar to the joints?

The mortar should be scraped onto the face of the pointing iron and then pressed into the joint to ensure good adhesion.

How should you determine the right time to work with the mortar?

You should wait until the mortar is 'thumbprint hard,' meaning it has set enough to hold its shape without being too soft or too hard.

Should mortar joints be smoothed out after application?

No, you should not slick down the mortar joints. Excess mortar should be scraped back until the desired joint profile is achieved.

How should the joint be finished after the excess mortar is scraped back?

The joints should be hit with a turn brush to remove excess binder from the surface, exposing the aggregate underneath and the edge of the brick.

What is the difference between a slick down joint and a properly finished joint?

A slick down joint is overly smooth and uniform, while a properly finished joint retains a textured profile and exposes the aggregate, which is essential for both appearance and function.

How does the appearance of colored mortars differ from regular mortars?

Colored mortars show an even greater difference in appearance when compared to slick down joints, highlighting the importance of finishing techniques in maintaining the desired look.

What should be avoided when finishing mortar joints?

Avoid slicking down the mortar joints, as this can negatively affect both the appearance and the durability of the mortar joint.