And I am just a civil engineer who gets to play with stuff! Three of my
favorite subjects but I will be brief;
* Coatings
* Brownstone
* Micro abrasives
Coatings whether liquid or cementious are not the problem, when handled
properly. It is the rate of moisture vapor transmission through the
interface or impregnated layer that makes the difference. Consider 3 pounds
of water per 100 square feet traveling out of the structure during the
winter (analogy used based on my ASTM work with debonding flooring materials
where the 3 pound rule holds strong). As the moisture travels in vapor or
moisture form ANYTHING that will impede the flow will, by definition, have
to cause a buildup of this excess at this point in the structure. As this
moisture continues to build up (3#'s reduced to 2.5# equals .5# buildup
every 24 hours for example) at the interface or barrier, as it always seems
to be within the freeze zone as it is close to the exterior surface, the 4%
rule takes over (Water to Ice expands 4%) and the weakest of the components
typically fails, the brownstone under layer! Stucco brownstones with pretty
but totally inappropriate score lines which never mate up with the actual
stone, age good for a maximum of 15 years in NYC, Period. Pages of
additional data and opinions withheld due to my sympathetic nature. Final
note; If a stucco, typically European previously, is applied and is less
dense, for the lack of a better tern, and is more breathable this is a case
where an applied stucco will work. Northern Germany uses brick as a base for
stucco. (softer over harder - case in point)
Brownstones - see above, but I will add a few comments. Having been involved
in the repair of brownstones for over 15 years and having used at least 4
different proprietary mixes and witnessed at least 7 different materials
used I do believe that under the right conditions which primarily depend on
substrate condition and the ability of the stone to actually perform in the
application intended, patching is a very viable alternative. However, based
upon my importation of natural brownstone I would like to dispel the myths
that there is no quality brownstone available for repair, restoration or in
fact new structures. Also brownstone makes an excellent landscaping material
when the right material is made available. I have seen ground contact
brownstone in perfect condition with installation dates going back to the
1200's. I will stop but along with my partners this is one of our favorite
subjects to discuss.
Micro abrasives - First, if you don't know the difference between JOS and
Rotec in both design and performance the rest of this may be academic. If
you think they are the same, please don't specify micro abrasives on
sensitive materials. Micro abrasive ranging from the abrasives included in
Sponge Jet material right through to the hydro abrasives (sandblasting with
water) should always be at least consider then eliminated individually based
on the projects needs and the systems properties and capabilities. Baking
Soda works great on steel but do you really want to use it on a masonry
project with substantial mortar?
I only bring up the above for continued discussion and concur whole
heartedly with Ken, and most of the time with Mike.
Thanks for the opportunity.
Pat M
PJM
_____
From: The listserv where the buildings do the talking
[mailto:[log in to unmask]] On Behalf Of Gabriel
Orgrease
Sent: Monday, January 26, 2009 7:11 AM
To: [log in to unmask]
Subject: Re: [BP] Removing fake brownstone
Edison Coatings wrote:
I am just a chemical engineer
And I am just a guy that gets to play with stuff.
I agree that control of water flow through maintenance of gutters, leaders,
roof systems etc. is way more of a factor in the deterioration of brownstone
facades than coatings. Though I really am solidly against the wholesale use
of cut-n-stucco techniques.
I have encountered situations, one in particular, where the sandstone (not
brown in this case) was coated so many times by maintenance staff that it
was the coating that held the stone together. Once the coating was removed
the stone crumbled, whereas everywhere else on the facade where maintenance
could not conveniently reach the stone was in noticeably better, though
admittedly poor, condition. So, I would prefer appropriate maintenance if it
is to occur at all. In my experience though knowledge is not very well
communicated to maintenance. Which brings up questions as to how knowledge
of anything gets disseminated into the built environment. Many times experts
are not brought in to see evidence in the field as there is no motivation to
involve them -- then the question is how do they learn?
If you don't have tons of water pouring into the wall system, letting it out
just isn't that big a deal.
Yeah, all you need is good flow, a few well placed holes.
...they just aren't seeing the predicted damage. DUH! But hey, don't
acknowledge those of us who questioned the conclusions on this subject 25
years ago.
I agree with your sentiment re: the back-n-forth on clear coatings. It is
curious to me that a quarter century can go by and yet there is no
conclusive consensus. One expert doctor will say it is good to beat
children, another expert doctor will say that it is not. Personally I find
the lack of consensus, and the constant reiteration of pro and con to be the
more interesting subject.
I remember a time when to say 'abrasive blasting' was suicide and that was
when I was playing with plastic media to remove epoxy paint from granite at
Carnegie Hall. Then came micro-abrasives and soda blast and all sorts of
chummy stuff.
][<en
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