Homes and History

Taking Care of your Historic Atlanta Home - Repointing Bricks

Pointers for making sure your home has many healthy years ahead.

Repointing Bricks

Check out this Preservation Brief from the National Park Service.  Most homes built prior to 1930 need softer N, O or K mortar mixes. (Capital letters go from hard to soft in MaSoN wOrK.) The extra lime & sand in these softer mortars allow for a greater amount of expansion & contraction in the damper crawl space (think of it as soft, healthy gums for your teeth)....do not use straight Portland cement (sidewalk cement, quick dry) as mortar - placing a mortar that is too hard between the softer bricks will cause them to crack and crumble as the seasons change.

Your existing mortar will likely differ from a premixed formula. The main priority is to make sure it's softer than the standard Portland Cement mix is  - with a greater lime content to self-heal small cracks. Here's how to visually inspect your mortar.

Unfortunately Type O is no longer sold in Atlanta at Home Depot or Lowe's.
(Currently looking for a source of Tuck Pointing Mortar (AMX 420) in the Atlanta Area.)

This helpful article provides a formula for Type O mortar:

1 part Portland Cement (Careful, avoid buying "Mortar" since it already has sand mixed in.)
2 parts Mason's Hydrated Lime - Also no longer sold at Home Depot or Lowe's
8 or 9 parts washed building sand

Add a little buff-shaded masonry cement just to tone it out, but not too much since it may look orange.

How to mix your own Type O from Type N
Type N is 1-1-6, Type O is 1-2-8. Where second number is lime, third is sand.
So for a 60 lb bag of Type N mortar, add 1 part hydrated lime (7.5 lbs) and 2 parts sand (15 lbs) to create Type O.
Found Hydrated Lime on Amazon


How to Apply
Clear to 1 inch using chisel or angle grinder.
Wet (drench) the existing bricks so they do not pull moisture out of the drying mortar.

If you want an exact match for the consistancy or color or your mortar, check out the Mortar Analysis and Matching Service at USHeritage.com

Don't let a mason water seal or treat the bricks (bricks DON'T need it). Avoid applying anything that cannot be reversed.
 

Avoid Over Vapor Barrier-izing

Be weary of over vapor barrier-izing your ground. This can focus "rising damp" into your piers where they touch the ground and create a faster capillary action of ground water concentrated right up into your wood structural members.