Technical Guide

Repointing Historic Mortar Joints
Cleaning and Repainting Pressed Metal
Repairing Wood Windows
Technical Guideline Regulations

Repointing Historic Mortar Joints

1. Removing failed mortar. Old mortar (including sound mortar) shall be removed to 2 to 2 1/2 times the width of the historic mortar joint. For instance, if the mortar joint is 1/4" wide, 1/2" of the mortar shall be removed. To provide a good bond, the depth of the joint should be 1/2" minimum. In order to protect the historic brick we recommend that the mortar, especially when the joint is very narrow, be removed using hand tools, such as a chisel and mash hammer, rather than power tools. If a contractor can prove that the same result can be achieved using small pneumatically-powered tools, he/she can use them on the horizontal joints only. The contractor should provide a test patch for approval prior to use of these tools. Power tools should never be used on vertical joints as they are likely to damage the adjacent brick. The mortar shall be removed to a uniform depth, leaving the edges of the brick undamaged.
   
2. Cleaning joints. Following the removal of the old mortar, the contractor shall rinse (no more than 100psi) the joints with water to remove any debris. This shall be done immediately prior to repointing to ensure the joints are damp when the contractor begins repointing.
   
3. Mixing mortar. When mixing the mortar, the contractor shall mix all dry ingredients first, adding water only after they are thoroughly mixed. The mortar shall be used within thirty minutes of being mixed.
   
   Suggested Mortar Types for Different Exposures
   

   Masonry Material	Sheltered	Moderate	Severe
   Very Durable: granite, hard-cored brick	O	N	S
   Moderately Durable: limestone, durable stone, molded brick	K	O	N
   Minimally Durable: soft hand-made brick	L	K	O
   Mortar Recipes
   	Cement	Hydrated Lime or Lime Putty Sand
   K	1	3	10-12
   L	0	1	2 1/4-3
   N	1	1	5-6
   O	1	2	8-9
   S	1	1/2	4-4 1/2

   
   
4. Applying the mortar. The contractor shall apply the mortar while the joints are damp. In order to minimize shrinkage, he/she shall apply the mortar in a series of layers. Each layer shall be approximately 1/4" deep. When each layer has set to a thumb-print consistency, the next layer may be applied.
   
5. Tooling the mortar. When the final layer of mortar has reached a thumbprint consistency, the contractor may tool it. The tooling shall match the tooling of the historic mortar. For instance, if the historic mortar has been raked, the new mortar shall be raked. The joints shall not be filled too full, which creates the appearance of a wider joint and makes the brick more vulnerable to sailing. Excess mortar left on brick may be cleaned off with a nylon brush 1-2 hours after tooling.
   
6. Project conditions. Do not repoint mortar joints or repair masonry unless air temperature is between 40 deg. F. and 80 deg. F. and will remain so for at least 48 hours after completion of work. If work during cold weather is necessary the following precautions should be used:
   * When air temperature is below 40 deg. F. heat mortar ingredients, repair materials, and existing walls to produce temperatures between 40 and 120 deg. F.
   *When mean daily air temperature is between 25 and 40 deg. F. cover completed work with weather-resistant, insulating blankets for 48 hours after repair and pointing.
   *When mean daily air temperatures above 32 deg. F., provide enclosure and heat to maintain temperatures above 32 deg. F. within the enclosure for 48 hours after repair and pointing.
   
7. Curing mortar. Cure mortar by maintaining in damp condition for 72 hours minimum. This may be accomplished using a hand spray bottle with a fine nozzle, spraying the walls every few hours for 2-3 days. A layer of burlap may be used to cover the new mortar to seal in moisture and protect it from the sun.

Cleaning and Repainting Pressed Metal

1. Removing paint. Contractor shall remove existing paint on cornice/sign using gentlest means possible. This may be accomplished using low-pressure water spray (test beginning at 60 psi, no more than 200 psi). If necessary to remove failing paint, contractor may use walnut shells with low-pressure spray.
   
2. Re-coating. As soon as the cleaned cornice is dry, contractor shall apply two coats of linseed oil iron oxide primer. When primer is dry (according to manufacturer's instructions), contractor shall apply final coat of high-gloss oil-base finish paint in colors as specified by owner.

Repairing Wood Windows

1. Remove Window Sash from frame. If repair of window mechanics is necessary, remove window sash from frame.
   
2. Removing Falling Paint Coating. Remove failing paint on sash and frame using handscrapers. Rinse or brush off debris and allow wood to dry.
   
3. Repairing deteriorated wood. Apply liquid epoxy such as Abatron's LiquiEpox or equivalent to consolidate deteriorated wood on sash and frame. Cure finish surface according to manufacturer's specifications. Apply epoxy putty such as Abatron's WoodEpox or equivalent to fill in gaps in wood. Cure according to manufacturer's specifications. Replace in-kind wood members are missing or broken/deteriorated beyond repair.
   
4. Repair window hardware and mechanics. Repair existing hardware and window mechanics, such as pulls, ropes or chains, where possible. Replace deteriorated mechanics and hardware in-kind where necessary.
   
5. Secure glazing. Inspect glazing putty. Remove deteriorated glazing putty and re-putty to secure glazing to muntons and sash.
   
6. Re-install. Re-install sash in frame.
   
7. Caulk. Caulk inoperable joints.
   
8. Prepare surface for paint. Sand surfaces of wood windows and doors to smooth epoxy and rough wood. Rinse or brush to remove residue from sanding. Within two days of the time wood is first exposed, apply linseed oil, prime with oil-based primer and paint with oil-based paint.