FAQ For Masonry Qualification

When developing a list of qualified contractors for a masonry restoration project, ask the questions listed below during the interview.

 

Choosing a Masonry Contractor

When developing a list of qualified contractors for a masonry restoration project, ask the questions listed below during the interview. These basic questions and their corresponding answers will help determine if you are dealing with a qualified masonry restoration contractor.

For Contemporary Masonry Work:

Q: What is a water-managed wall as opposed to a barrier wall? 
A: A water-managed wall is a system designed to control and evacuate any water that enters the wall. One type of water-managed wall is called a “cavity wall” – it has through-wall flashing that directs moisture to weep holes on the outside surface of the wall.

A barrier wall is solid, and is designed to act as a barrier to prevent any water infiltration. A properly maintained solid brick, stone, or poured concrete wall is usually fairly effective in this capacity.

Q: What will be your temporary shoring pattern when removing masonry to replace a standard three course flashing system?
A: The answer to this question will likely be different depending on the specific details of your job. The most important thing is that there is an answer … that shoring will be used, and that the contractor is able to explain their shoring system.

Q: How are you going to control dust while cutting and/or grinding out the mortar joints?
A: There are several ways to control dust while cutting or grinding out mortar. A few possibilities are:

  • use grinders with vacuum attachments
  • tent the work area with fabric or mesh
  • wet the wall down before grinding

Q: What is the depth for the brick mortar removal?
A: Three times the width of the mortar joint. If the mortar joint is ¼” wide, the removal depth should be ¾”.

Q: What kind of wall tie will you use when rebuilding?
A: Ladder-type wall ties may be used along the length of a row if rebuilding a relatively long run of brick or block.

Helical anchors are often used to repair existing walls in selective spots that have insufficient existing wall ties. They are also often used to tie the outer wythe (wythe: a layer 1 masonry unit wide) of a wall to the inner wythe, or they may be used at an angle to stabilize an existing crack.

Q: Will you salvage the brick and, if so, how? If not, do you know where to find similar brick?
A: It is not always necessary or feasible to salvage brick. Brick that is particularly soft or deteriorated may not be wise to save and reuse. If a building’s brick type is still in production, it is often more cost-effective to simply order new brick.  If mortar is still adhering particularly well to a removed brick, it is often time-consuming and difficult to sufficiently remove the attached mortar in order to put it back into the wall. The Brick Institute of America does not recommend reusing brick because the pores filled with existing mortar will not allow for cementitious root growth, and therefore not allow proper mechanical bonding between the brick and the mortar joint.

If the structure has been designated a National Historic Landmark, is eligible for historic tax credits, is within a historic district, or is otherwise encumbered by special regulations or circumstances, it is best to check with the appropriate agency about guidelines regarding removal, reuse, or replacement of existing materials.

Q: What mortar mix type (ASTM designations: M, S, N, O, K) do you plan on using and why?
A: The letters listed above refer to a mortar’s compressive strength and composition. Mortar with the designation of “M” has the highest compressive strength.  Keep in mind that a harder mortar is not necessarily better. For example, deterioration of comparatively soft bricks may be accelerated by a mortar that is too hard.

Whatever mortar mix is chosen, the contractor should be able to intelligently discuss the reasons for their choice.

In addition to the contemporary mortar mix outline above, lime putty mortar, natural cement, or natural hydraulic lime may be considered when re-pointing. Age of the structure will help determine which mortar to use. The most important part is to have a mortar analysis performed to determine the original mortar design.

Q: How will you integrate and attach the new flashing system to the existing wall?
A: A termination bar attaches the new flashing to the backup wall and a bead of sealant is applied along the masonry to termination bar joint.

Q: What is an end dam?
A: An end dam is an integrated part of a flashing system that should be found at locations where there is a fenestration and/or a termination of the flashing system. An end dam is essentially an inside or outside “corner” of flashing. Metal flashing can be used with an upturned and sealed corner, or an end dam can be created out of a flexible flashing product by folding and sealing.

Q: Are you using backer rod or bond breaker tape prior to the caulking?
A: Caulking is most effective when it is adhered only to two surfaces. Backer rod is a flexible cylindrical foam product that is often placed in joints prior to caulking to ensure that only the two intended sides adhere. Caulk will not stick to the backer rod, so the backer rod is simply a ‘spacer’ that prevents excessive quantities of caulk from pouring in and filling up a cavity.

Bond breaker tape is used with the same intent as backer rod – to “break the bond.”  The difference between bond breaker tape and backer rod lies in the fact that bond breaker tape does not act as a “spacer.”

Q: Are you using a primer for the caulk?
A: Primers are used as a surface preparation prior to caulk application. In some cases, primers may be required by the caulk manufacturer for their product to be guaranteed. In-place mock-ups and a sealant adherence pull test will establish if a primer is required

Q: What is the width to depth ratio for the caulking you are planning to use?
A: The depth of a urethane sealant is typically ½ the width of the joint.

Q: What kind of testing or mock-ups can be used to insure a successful project?
A: When undertaking a large job, it is wise to ask if the contractor would install a sample (or mock-up) of the work they intend to perform. For example, a company that has been contracted to perform 100% of the re-pointing of a structure should be willing to re-point at least a 2’x2’ section of wall as a visual guideline for the owner/architect.

 

For Historic Masonry Work:

Q: What is the existing mortar mix? If it is unknown, how will you find out the mortar content? 
A: There are a wide variety of mortars that may have been used in historic buildings. Some of these mortars, especially on buildings constructed prior to the 1870’s, do not include any Portland cement, a common ingredient in modern mortars. In many cases, a pre-bagged mortar may not be available to match the existing, and a custom mix will have to be created. It is often recommended that mortar samples from various locations on the building be taken and sent out to a lab for testing to determine the appropriate mix design.

Q: How are you going to control dust when cutting and/or grinding out the mortar joints? 
A: Same answer as with contemporary question above.

Q: Will you salvage the brick and, if so, how? If not, do you know where to find similar brick?
A: Same answer as with contemporary question above.

Q: How do you plan on cutting out the mortar joints or extracting the brick without damaging the surrounding masonry or adjacent surfaces?
A: Mortar can be extracted by hammer and chisel, grinders, or pin routers. The goal is to not damage the brick in any way.

Q: To what depth will you cut out the mortar joints?
A: Same answer as with contemporary question above.

Q: How many lifts are necessary to re-point ¾” of removed mortar?
A: Though not always specified within contract documents, three ¼” lifts will ensure a better mechanical bond than one ¾” lift.

Q: What kind of testing or mock-ups can be used to ensure a successful project? 
A: Same answer as with contemporary question above.