By the BSA Historic Resources Committee, the Conservation
Forum, and APT/Northeast Panelists: Tony Golden, Chapman Waterproofing Co., Inc.;
Evan Hankin, Hankin Construction Inc.; Paul Capobianco,
Brisk Waterproofing Co., Inc.; and Bill Whall, Phoenix Bay
State Construction Co. Moderators: Wendall Kalsow, McGinley Kalsow Architects,
and Ivan Myjer, Building and Monuments Conservation Wendall asked each panelist to speak to the central issue
of mortar mixes from the perspective of the masons on the
scaffold. Tony Golden began with a working foreman's overview.
Tony's first point was that workability is the key
characteristic for every mason and that most mixes that are
specified (1:1:6 for example) are too sandy to achieve the
plasticity that clean work with a trowel demands. This leads
inexperienced masons to add water. More experienced masons
cut back on the percentage of sand. Tony teaches his workers
how to protect their sand from wind, rain, and cats. He
trains good mixers to start by measuring the components of
their mix including water. After a quantified start, a good
mixer can work accurately and consistently with the shovel
as a measure. A good mixer will also adjust water content to
suit shifts in the weather, temperature, and porosity of
masonry units. Tony's take on the trend towards Type O mortars and lime
mortars is that it may be problematic in our harsh climate.
His concern is that higher lime content may increase long
term vulnerability to freeze thaw cycles and mortar
washout. Tony urged specifiers to relax about using grinders for
cutting and raking out mortar joints. He is convinced that
in most cases they cause much less spalling of brick edges
than hammer and chisel work. Even when small air guns with
toothed carbide chisels are used, he likes to get a saw cut
into the joint first. Many specifications call for pointing
in lifts, but Tony warns that cold joints can cause trouble.
Good masons can make their first lift wetter than the final,
then go back and to add mortar, pack and finish within a
single period of work. Tony is a fan of premixes and understands that we like to
know what they contain, but does not support a blanket
prohibition of "masonry cements" since for small batch jobs,
only sand is left to measure. His final, and most
provocative, plea was for pre-hydration of mortar creating a
dry-pack to which the mason then adds water for a pointing
mix after an hour of "rest." [This advice left Evan
Hankin swelling with indignation.] Paul Capobianco addressed the contractors' problem of
turnover within their crews (especially on large jobs) and
maintaining consistency of workmanship. He introduced a
concern about silicosis and noted that workers' safety is a
growing concern. Paul aims to establish a stable crew for
each project, to get them measuring consistently and to work
with the architect or engineer to get the team working well
with the building. His impression is that the most
experienced specifiers and architects are the most open to
suggestions from the contractor. Evan Hankin was trained as an engineer and brings a
different perspective to some basic field questions. He is
opposed to pre-hydration of mortars because in his view, it
starts the chemical process and adding more water later may
damage the crystallization matrix: crystals are being broken
down and may not reform. Evan noted that this must reduce
compressive strength and that both bond strength and
flexural strength are related to compressive strength, they
must also be reduced. The only virtue of pre-hydration Evan
could see would be less shrinkage. Evan underscored Tony's points about mortar workability.
Specifications often ask for the contractor to analyze and
match the existing mortar, but this may not lead to a mix
that will stay on the "jointer." Workers in the field won't
mess around. If the mix is too "bony" they cut back the
sand. If it is too dry, they add "wine" somewhere, often
pre-wetting the joints with spray bottles. Evan also spoke
out against the specification of white cement for pigmented
mortars, noting the limits to pigmentation and the greater
ease of matching mortars with gray cement as the base. Evan
also believes that measures by the shovel pose no threat to
consistency. Bill ("You really have to work to ruin mortar.") Whall
started by saying how seldom he sees mortar fail. It may be
too hard or messy or difficult to apply, but it tends to
last. He characterized Type O mortar as "swill" with the
1:3:9 variant feeling like popcorn (especially with concrete
sand), but he still thinks it is indestructible. (25 years
and looking good at Met Life). Bill encouraged architects to
hold their ground when they want difficult aggregates and
Type O mortar, but reminded us that "1:3:9 goes so
reluctantly into the wall." He warned against the huge range
of variation in the appearance of aggregates, even with
bagged sand. Bill did warn against the excessive shrinkage that seems
to come with mortars that are too rich in cement (too little
sand). He also noted, without speculating on why, washing
seems to trigger efflorescence. Most of the panelists seemed
to find that efflorescence is more often related to the
brick than to mortar, and each has been watching the Long
Wharf Marriott with its over 15 years of "new building
bloom." Bill tries to limit the amount of water his teams
introduce into unit masonry, including during wash-down and
especially at the end of the season. Questions and comments: Ivan Myjer pointed out that water content remains the
wildest card in mortar mixes for both appearance and
strength. Especially since the moisture content of
aggregates varies so dramatically. Bagged sand is kiln dried
and has almost zero water content. Lisa Howe asked if unions help train masons for
restoration work. Bill Whall said that training for pointing
and caulking is getting much better and that apprenticeships
are effective. Tony Golden said it is difficult to keep
teams together because winter layoffs mix everything up. He
also said that there are plenty of bricklayers who cannot
point and pointers who can't lay brick. Bill Whall remarked that the culture of masons is highly
competitive and success is measured in linear feet of
pointing or square feet of wall raised. This may lead to a
poor distribution of skills. Ted said a good foreman can
manage about 15 - 20 masons and may put together a team that
has a good mix of abilities. Ivan Myjer pushed back on "masonry cements" saying that
they tend to contain unknown amounts of soluble alkalis and
that these can stain. However, factory batching of
components is obviously useful when we are told what they
are. White cement often has a lower soluble alkali
content. Evan Hankin made a final plea that our specifications
never again use the words: "as required."