Dear Morte:

I want to get ugly paint off the bricks of a house I just bought. Should I sandblast?

Signed, Brick Lover in Florissant

Dear Brick Lover:

Only if you really hate the house. It’s almost impossible to avoid using excessive
pressure when sandblasting. Too much pressure exposes the softer, inner
portion of the brick to the ravages of weathering. Cracking between brick and
mortar appears, and wind-driven rain can get in. A kinder, gentler cleaner is
needed, even if it costs a few bucks more. That is, unless you want to get rid
of the house. Then either sandblasting or dynamite will do the trick.

Morte

Dear Morte:

I’m designing a one-story building for a military arms supplier. Should I specify
masonry prism tests?

Signed,  Architect in Clayton

Dear Architect in Clayton:

Only if the supplier is going to store US Army tanks on the roof. Unless the
walls have some very unusual loading, a one-story building will have low
compressive stresses. Instead of expensive prism tests, call for the unit
strength method of verification. With this method, the contractor must certify
that the mortar used is the type specified and submit net compressive strength
of the masonry units. The compressive strength of the masonry wall can then
be determined using tables from the building code requirements. Prism tests? 
No TANKS.

Morte

Dear Morte:

Are high-lime mortars recommended for pointing historic masonry structures?

Signed, A Mason Contractor

Dear Mason Contractor:

A soft mortar should be used whenever you repair older structures since
hard mortars can cause the older masonry around the repaired area to spall.
Mortars with lower compressive strengths will not concentrate forces at the
face of the wall and can, therefore, prevent damage.  However, be sure the
mortar is durable.  In areas where freeze-thaw durability is an issue, use
Type N mortars with the maximum lime and sand allowable by ASTM C270.

Morte

Dear Morte:

Is there a difference between the terms “tuckpointing” and “repointing”?

Signed, A St. Louis Architect

Dear St. Louis Architect:

According to the Brick Industry Associations (BIA), there is a slight difference.
Tuckpointing refers to the act of placing new mortar in defective joints.
Repointing is the act of cutting out defective joints and replacing them with
new mortar.

Morte

Dear Morte:

On a recent project, the face brick varied in length quite a bit – up to 1/4 inch.
To compensate, I laid the brick with head joints varying in size from 3/16 to
1/2 inch. The work looks real good, but what’s your prognosis for performance
in the long haul?

Signed,  Curious Mason in Brentwood

Dear Curious:

Good news. That wall’s going to outlast you and me, maybe even my
mother-in-law. Tolerances in a brick wall are a lot more forgiving than they
are in something like the space program. Head joints in running bond masonry
contribute little to the strength of a wall, so you’re OK there. But what you’ve
got to look out for is water leakage. By mortaring the head joints full, you
guard against that problem. It’s like my mother used to say: A full head will help
you avoid problems.

Morte

Dear Morte:

I’ve got ivy growing on the brick walls of my house. My wife wants me to pull
it off because she thinks the ivy is destroying the brick. I disagree. We even
have a bet on it. So who’s right?

Signed,  Ivy Lover in Afton

Dear Ivy Lover:

Have fun doing the laundry, waxing the car or whatever, because you lose!
The Brick Industry Association (BIA) estimates that deterioration by ivy can
reduce the life of a well-constructed wall of quality materials by up to 10
percent. More if the wall isn’t well made. Putting it simply: ivy eats brick, you
eat crow.

Morte

Dear Morte:

As a recent graduate from Architecture school, I’m new to architecture and to
the St. Louis area. I’ve noticed that bricks at area job sites are stacked on
wooden pallets. Can you tell me why pallets are used? The bricks are going to
get wet anyway. Why not just leave them on the ground?

Signed,  New in Town

Dear New Architect:

St. Louis has been a national leader in brickwork for 150 years. After all this
time, we know how to do chicken right! You put brick on a pallet for the same
reason you put your car in a garage – you want to protect it. Brick shouldn’t
be left directly on the ground because the units can absorb salts from the soil
that can cause efflorescence, which shows up as discoloration of the walls.
Brick also needs protection from the dirt that can splash onto the units and
ultimately reduce the masonry’s bond strength. So give your brick a break.
Protect them. Your walls will thank you.

Morte

Dear Morte:

The specifications on my rehab project call for reusing old brick since it looks
like the original material. Is this a good idea?

Signed,  Contractor in Festus

Dear Festus:

Well, if the building owner is into gambling big time, it’s a great idea because
used brick is a definite crapshoot. First, the surfaces of used brick are often
filled with mortar particles or dirt, preventing a good mortar bond. As a result,
the joints may be inferior and there’s a good chance of water getting in. 
Second, when old buildings are torn down, the surface and back up brick
tend to get mixed up together. If the old back up brick is put on the surface of
the new project, the owners could be facing problems down the road. The
smart bet is to avoid problems by avoiding used brick or at the very least, use
it very, very carefully.

Morte

Dear Morte:

My memory, like everything else, is going bad.  How far are the ends of cotton
wicks supposed to go up into a masonry cavity?

Signed,  Forgetful Mason in Maplewood

Dear Forgetful:

I sympathize with your condition, so here’s an answer you can remember: 
Zero. There are other ways of weeping walls that will give faster draining. 
Leaving open head joints, using weep hole ventilators, or pulling wicks after
completing a section are three good alternatives. But if your boss insists on
wicks, I recommend about 8 inches of cotton sash cord within 4 inches above
the base of the flashing. Ideally, the cord should extend one inch past the face
of the exterior brick to form a drip; however, the ends can be cut off at the
face of the brick to avoid a fuzzy look.

Morte

Dear Morte:

What is the difference between control joints and expansion joints and how
do I know where to use each? Shouldn’t the mason contractor know where
to place them?

Signed,  Architectural Intern

Dear Architectural Intern:

This is a good questions and the answer should be learned early. Space here
is limited but here goes.

You would think that since clay expands in the wall during its curing process
that it would make sense that control joints (CJ) would be used for clay. But
that’s not the case: an expansion joint (EJ) used. An EJ on the on the drawing
should be free of mortar or other obstructions to allow the wall to expand
without cracking, chipping or spalling. Often compressive filler is called for to
assure the joint is free of mortar. Using this designation allows the writer of
the specification to know to spec mortar free joint.

Concrete, on the other hand, will shrink as it cures. This would lead you to
believe the abbreviation should be SJ for shrinkage joint, but no it is CJ for
control joint, which will control the location of the cracking like a joint in a
sidewalk. These joints are usually mortar joints, raked back and filled with
caulking.

By the way, both clay and concrete will expand with thermal change, so do
we need TJ for that? No, EJ works just fine.

As to location, unless you don’t care about the appearance of your design you
should take the time to show where the joints should go. Besides, the code
(MSJC) says joints should be shown on the construction documents by the
design professional.

You’ll want to memorize the terms and their abbreviations since the proper
terminology is important in the bidding and execution of the project. By the way,
NCMA and BIA both offer technical notes giving calculations for joint location
as well as rule of thumb location.  Thanks for your question and good luck with
your career.

Morte

Dear Morte:

I have had several code officials ask me about U.L. labels on block for
firewalls. I’m kind of hazy on what they mean. What can you tell me about
labeling?

Signed,  A Mason Contractor

Dear Mason Contractor:

Since there are several hundred block (CMU) manufacturers in the country, it’s
not realistic to believe that they all could go through the process of testing all
their units to establish fire ratings.  Services such as Underwriters Laboratories
(U.L.) are happy to test various types, aggregates and sizes; however, there
are alternative methods available.

The most common procedure is the equivalent thickness method, which has
been developed through research and calculations to show the fire rating for
masonry units.  Both NCMA and BIA have published technical documents on
this method, which has been acceptable to Codes for years.

After several years of deliberation, a joint committee of the American Concrete
Institute (ACI) and The Masonry Society (TMS) published a consensus
document Standard Method for Determining Fire Resistance of Concrete and
Masonry Construction Assemblies ANSI/ACI 216.1-97, TMS 216-97. Copies of
these documents are available from MISL.

Morte