Repointing is both expensive and time consuming due to the extent of handwork
and special materials required. It is preferable to repoint only those areas
that require work rather than an entire wall, as is often specified. But, if
25 to 50 per cent or more of a wall needs to be repointed, repointing the
entire wall may be more cost effective than spot repointing.
 When repairing this stone wall, the mason matched the raised profile of the original tuckpointing. Photo: NPS files. |
Total repointing
may also be more sensible when access is difficult, requiring the erection of
expensive scaffolding (unless the majority of the mortar is sound and unlikely
to require replacement in the foreseeable future). Each project requires
judgement based on a variety of factors. Recognizing this at the outset will
help to prevent many jobs from becoming prohibitively expensive.
In scheduling, seasonal aspects need to be considered first. Generally
speaking, wall temperatures between 40 and 95 degrees F (8 and 38 degrees C)
will prevent freezing or excessive evaporation of the water in the mortar.
Ideally, repointing should be done in shade, away from strong sunlight in
order to slow the drying process, especially during hot weather. If
necessary, shade can be provided for large-scale projects with appropriate
modifications to scaffolding.
The relationship of repointing to other work proposed on the building must
also be recognized. For example, if paint removal or cleaning is anticipated,
and if the mortar joints are basically sound and need only selective
repointing, it is generally better to postpone repointing until after
completion of these activities. However, if the mortar has eroded badly,
allowing moisture to penetrate deeply into the wall, repointing should be
accomplished before cleaning. Related work, such as structural or roof
repairs, should be scheduled so that they do not interfere with repointing and
so that all work can take maximum advantage of erected scaffolding.
Building managers also must recognize the difficulties that a repointing
project can create.
 A mechanical grinder improperly used to cut out the horizontal joint and incompatible repointing have seriously damaged the 19th century brick. Photo: NPS files. |
The process is time consuming, and scaffolding may need
to remain in place for an extended period of time. The joint preparation
process can be quite noisy and can generate large quantities of dust which
must be controlled, especially at air intakes to protect human health, and
also where it might damage operating machinery. Entrances may be blocked from
time to time making access difficult for both building tenants and visitors.
Clearly, building managers will need to coordinate the repointing work with
other events at the site.
The ideal way to select a contractor is to ask knowledgeable owners of
recently repointed historic buildings for recommendations. Qualified
contractors then can provide lists of other repointing projects for
inspection. More commonly, however, the contractor for a repointing project
is selected through a competitive bidding process over which the client or
consultant has only limited control. In this situation it is important to
ensure that the specifications stipulate that masons must have a minimum of
five years' experience with repointing historic masonry buildings to be
eligible to bid on the project. Contracts are awarded to the lowest
responsible bidder, and bidders who have performed poorly on other projects
usually can be eliminated from consideration on this basis, even if they have
the lowest prices.
The contract documents should call for unit prices as well as a base bid.
Unit pricing forces the contractor to determine in advance what the cost
addition or reduction will be for work which varies from the scope of the base
bid. If, for example, the contractor has fifty linear feet less of stone
repointing than indicated on the contract documents but thirty linear feet
more of brick repointing, it will be easy to determine the final price for the
work. Note that each type of work--brick repointing, stone repointing, or
similar items--will have its own unit price. The unit price also should
reflect quantities; one linear foot of pointing in five different spots will
be more expensive than five contiguous linear feet.
"Repointing Mortar Joints" an Historic Preservation Brief
