[TheForge] Re: interesting project

[terry l. ridder]

On Tue, 20 May 2003, Joe Chadwick wrote:

<snip>

terrylr> the house is a historic house in dekalb, illinois.

joe> 
joe> Is there a named historic certification or district that would trigger an 
joe> approvals/ review process?
joe> 

no.

terrylr>
terrylr> the house was built
terrylr> in the late 1800s or early 1900s. it is an eggshell colored terra cotta
terrylr> brick and stone mansion.
terrylr>

joe> 
joe> I'm not familiar with the grades of brick clay common in Illinois, but you 
joe> need to know some specific things about the porosity and absorption rate of 
joe> the material before you get too far. Then you need to know about how the 
joe> brick was fired.
joe> 

the people at great lakes clay are working on that.

terrylr>
terrylr> the main roof the part copper and part tile.
terrylr> the main roof is fine. the problem is the single story, flat roof,
terrylr> "breakfast" porch. someone in the last century tarred the roof. they
terrylr> were not to careful as to where the tar oversprayed. roughly fifty feet
terrylr> of copper sheet roofing to partial covered with tar. approximately 35
terrylr> square feet of stone work and brick work is either covered with tar or
terrylr> has severe overspray.
terrylr>

joe> 
joe> Before you go removing it, does anybody know why it was put there in the 
joe> first place? (did the roof leak? the seams? the joints?)
joe> This "tar" could be coal tar, roofing asphalt, or a form of rubberized 
joe> asphalt. Each have a slightly different removal protocol.
joe> If it is a low slope roof, and in fact sprayed, it suggests a rubberized 
joe> bitumen emulsion. The over-spray could have been an attempt to either 
joe> liquid-flash the roof-house joint or provide some degree of moisture 
joe> protection to the side wall from snow accumulation. If this goes away, and 
joe> the removal process affects the surface, the moisture accumulation in the 
joe> masonry is the quiet start of a disaster.
joe> 

someone previous occupant in the past put up an awning that attached to
the side entrance way to the house/mansion. the side entrance way leads
into the single story "breakfast porch". the awning was not at roof
height about 2ft below it. the tar was used to seal the seam between the
awning and the masonary (stone and brick work). the awning was removed
for the current restoration project. given the overspray pattern i would
bet that the tar was mopped/brushed on.


terrylr>
terrylr> given the age and composition of the brick and stone work acid or base
terrylr> cleaning is out of the question.
terrylr>

joe> 
joe> Maybe, maybe not..
joe> 

the carriage house had a few loose bricks which i used for
experiementing today. muratic acid dissolved the brick in little time.
lye caused iron stains on the brick. the brick is nearly ivory in color
or an extremely pale yellow.

<snip>

terrylr>
terrylr> the national park
terrylr> service site on restoration of historical sites suggests using liquid
terrylr> nitrogen to freeze the tar and chip it off the metal with plastic or
terrylr> nylon tools. that seems like a reasonable possibility.
terrylr>

joe> 
joe> whether or not it is Coal tar or asphalt or rubberized bitumen makes a 
joe> big difference.
joe> 

terrylr>
terrylr> the masonary ( stone and brick ) is a different problem. the moisture
terrylr> content of the brick and stone would seem to prevent the use of liquid
terrylr> nitrogen. the fear i have would be that will freezing the tar and
terrylr> hydroscopic moisture content of the mansory would also freeze and cause
terrylr> the masonary to crack or spall. abrasive removal is out of the question
terrylr> since the stone work is soft stone. so how to remove the tar from the
terrylr> masonary. again in researching the web several commerical products were
terrylr> suggested. upon reading the msds they all contain dichloromethane
terrylr> (methylene chloride), xylene, and ethyl benzene. dichloromethane and
terrylr> ethyl benzene are listed as carcingens. the safety measures required to
terrylr> work with these chemicals and given the close proximity of neighboring
terrylr> houses really prohibits their use. the hazardous waste disposal would
terrylr> also tend to be cost prohibitive.
terrylr>

joe> 
joe> Depending on the solvent and porosity of the substrate and ambient vapor 
joe> pressure, one can drive the stain even deeper into the material with some 
joe> of these solvents.
joe> 

totally agree. given the above experiementing i have performed all ready
today i have serious reservations about using any type of solvent. the
brick is extremely porous. using solvents would probably just cause the
tar stains to bleed into and further out on on the brick surface.

<snip>

joe> >btw, this project has to be done by the weekend. there is a party at
joe> >this house on saturday of roughly 150 people.
joe> 
joe> I hope that party is sufficiently interesting to keep everyone's focus on 
joe> the party. I doubt that this can be resolved in a week....or recalling one 
joe> of Frank Lloyd Wright's bromides, "Doctors can bury their mistakes. All an 
joe> Architect can do is to advise the client to plant ivy." ...Flower pots on 
joe> the roof?
joe> 

the problem is that the tar and overspray are directly over the side
entrance way to the house/mansion. it is extremely noticable.

-- 
Terry L. Ridder ><>