Sharpshooter,

I was thinking someone with professional intelligence would answer by now, but
since they have not I'll throw in my lay remarks.

In most cases removal of the brick work, which can be the full height of the
building and generally 2 feet on either side of the corner, is due to the fact
that a long crack has developed. The crack will often run through the masonry...
right through the bricks, and not only through the mortar joints. The reason,
usually, for the crack is that the steel column on the interior of the corner has
rusted and due to rust jacking (an incredible force of expansion due to rusting
of the steel column, and beams, and beam connections <a scary scenario develops
of the skelton of the building disconnecting> -- and the engineers can tell you
just how much force is involved in rust jacking -- in my mind comparable to using
a 40 ton hydraulic jack to bust a brick -- by the by, how many people on BP have
experience using a hydrualic stone/brick splitter?) the masonry has been pushed
apart.

When a crack develops it allows more water to come into the situation, which with
oxygen causes more rusting of the steel. Maintenance, a dirty word on some days
as the most damage on a masonry structure seems to occur where maintenance
personnel can reach (a sociological logisitcs problem in urban environments),
usually consists of putting a sealant in the crack. Sealants are ok if they are
maintained, usually they are not maintained and the property owner goes along
with the subliminal imagination that their problem has been taken care of. In the
mean time water continues to get into the masonry and to cause rusting of the
steel. As the steel rusts the cross sectional area diminishes... sometimes to the
point of there being no solid steel left.

You will often see high-rises with "snakes" of sealant joints on the corners...
they also tend to a terrible match for the reason that idiot contractors, doing
maintenance or Local Law 10/11 work, do not expend resources in custom sealant
colors, and sealants always collect atmospheric dirt faster than the surrounding
masonry, let alone UV degradation... sealants have a limited lifetime, one much
shorter than brick. So the situation gets to a point that the owners, or someone
with a checkbook, decides something has to be done and a "professional" is called
upon to prognosticate. And then a decision is arrived at by the project team as
to what to do -- though it is the design professional that leads the design
process, including engineering as required.

You either get the weaved (called "stitching" at my end of the spectrum) corner,
or the corner with one side weaved and the other as an "expansion joint". In one
case we got to do an expansion joint on both sides of the corner... but that was
an exception for which I will fail to digress. The idea is that the project team
uncover the steel column and beam ends, look at it, and do something along the
lines of preventing the situation of rust jacking from getting worse. Steel
repairs may occur along in here, consisting in general of welding of reinforcing
plates to the existing steel. I've not done one of these projects yet without
application of one form or another of coating to the steel with the intent to
minimize the future process of rust... though in general the steel columns are
not exposed on all sides and so there always remains the "other" side encased in
masonry that does not get waterproofed. A situation, at least in my experience,
may exist where the masonry is taken down, the brick is gone and the steel is
exposed, and the project stops while everyone scratches their head because of the
revealing of "hidden" conditions. Hidden conditions provide design issues, they
also bring up cost issues. All of these issues tend to need to be resolved before
the project proceeds. With every individual design professional, and project that
I have worked on a corner, the approach and the solutions have been different.
There is no consistency of approach between one design professional and another.

The idea between the vertical expansion joint is to allow for movement of the
masonry at the corner. My impression is these structures were built prior to an
awareness on the part of design professionals and builders of the movement of
large walls of masonry due to thermal expansion/contraction, as well as lesser
effects of vibration and wind load. Vibration from the subway and street traffic
does have an effect on the performance of buildings. So, you get a vertical
expansion joint filled with sealant, sealant that has a shorter useful lifespan
than brick, on one side of the corner, and the other sides is stitched. Thermal
expansion/contraction in masonry is, for me at least, an incredibly dramatic
event. When the masonry is cold it shrinks and the sealant joints flatten out,
when the masonry is hot it expands and the sealant joints get squeezed, sometimes
bulging out of the joints. Sealants take a lot of shit from masonry abuse as the
expansion/contraction occurs on a daily basis. The most movement is with a full
sun passing a masonry wall with a southern exposure. The south wall will, in
general, have more movement than the north wall... so the building system
experiences an uneven distribution of the movement of thermal
expansion/contraction. Complications can arise when one building is shadowed by
another building, such that an angled area of the top of the building gets solar
heating but the lower portion remains in the shade, and therefore is relatively
cooler. Diagnoses of the relationship between an urban masonry building and the
natural environment is a complicated problem and requires due diligence in
thinking aobut what the hell is actually going on, then, what to do about it. It
is not enough to only read the building, the entire environment as a whole needs
to be read.

When you get both sides of the corner stitched it is because someone either did
not think to do an expansion joint, or did not think it necessary. I suppose in
some cases it may be just fine not to have an expansion joint.

The interesting problem with an expansion joint is that it is a cut through the
masonry and now, in essence, the corner is detached from itself. The remedy for
this, I suppose, and I say this with reservation as I am wanting to wait another
50 years to see what happens where expansion joints have been installed, is to
attach masonry ties to the steel column. This gets into all kinds of fun with
decision as to what type of steel to use for the ties (stainless or galvanized)
as well as design of the ties (their shape), how to anchor the ties to the steel,
how to integrate the waterproofing with the ties (every tie representing a hole
in the waterproofing), and pull tests to make sure the ties will not arbitrarily
separate from the steel column within an expected performance tolerance.

Why do the brick not match? Well, the brick made today is not the same brick made
in the 1930's and 40's. The source of raw materials, the technology of
manufacture, and the ownership of business has changed. Custom matching brick can
be had for a cost and for a long wait... minimum orders tend to the 10,000 brick
range, and the word on the street last I listened is an 18 month wait (though
like with a stock quote it all varies from day to day). There is a huge market in
NYC for brick to match to older buildings and manufacturers and suppliers are
working to fill the needs of the rehabilitation market. The demand is erratic.

The way in which brick is selected for a project is usually bass akwards... the
responsibility is made a part of the contract bid for the contractor to find a
suitable matching brick. I am increasingly of the belief that the identification
and availability of a matching brick should be determined in the pre-contract
design phase before the project ever goes to bid to contractors. One project that
we did, in which the brick did not quite match, and it still makes me sick to
think about it, resolved to problems of communication between us and the design
professional and suddenly here are 10,000 brick, slightly off in color match,
being delivered to the job with a full crew of masons ready to go. A forced
decision is often made as to selection of brick. Searching for a matching brick
is a pain in the ass and for the contractor it is a situation of being forced to
bid on a very high-risk situation... nobody knows at the time of bid just what
they will have to do in order to come up with an acceptable brick. If we are all
lucky there are enough brick sitting in a yard in Long Island City or PA. If
unlucky the contractor gets to go chasing after a custom brick -- this can be a
pleasant adventure, or a trip through hell. The spread in cost, the headache
involved, between one and the other is large. Into this mix we add that all
individual members of a project team have different levels of experience and
different agendas. This is where project management interfaces with materials
selection. If nobody on the project understands or cares to match the brick then
you will likely get unmatched brick. I think this idea of having the contractor
select the brick goes is a throwback to the practice of new construction and I
see that a greater awareness of the systemic supply-demand problem is occuring.

One suggestion that I have been spreading for several years is that the NYC
School Construction Authority, having a large number of buildings with identical
brick, knowing that they will have to use a lot of brick on many buildings, hire
a design team to survey the system-wide NEED for brick on the schools and to
research the availability of brick from the manufacturers. What does occur, as
far as I can tell, is that each individual school project goes through a brick
search process via the resources of the contractor... and, of course, each
contractor charges for their services to be repeated from school to school -- for
which replication of activity and cost the taxpayers pay. My suggestion is that a
design team, working with contractor and supplier consultants, be hired by the
SCA to search for brick once. Even if the study does not identify 100% of the
need for brick, the process would certainly define the future potential need in
such a manner that it could be communicated to the manufacturers. If a
manufacturer knows there will be a demand then they can adjust to accomodate and
provide units at a lower cost.

Then again, one ruling philosophy is to match the brick to a clean brick... and
the brick seen on the bulk of the building is a dirty brick, but is clean on the
inside. There is a sensible reason for matching to clean brick... and if we wait
long enough the new brick should get dirty.

Hope this helps.

][<en



Met History wrote:

> I see corner reconstructions on older steel-frame buildings done in two ways.
> One way is to "weave" the new brick into the existing running bond pattern.
> Another way is to create a completely new "column" of brick (usually in a
> terrible match), with a caulked joint running straight up.
>
> What's the difference?
>
> Christopher Gray