Q:
Which Lucas Elastomeric Coatings are right for my roof?
A: Please
refer to this guide.
Q:
Which are better, solvent or water-based elastomeric coatings?
A: Solvent
and water-based coatings each have their advantages.
Solvent based
tend to be more waterproof, can be used in colder weather, won't
freeze, are less affected by humidity and rain after application and
will adhere to certain surfaces, such as TPO, that water-based
coatings often will not.
Water based
coatings are lower odor, are "breathable" so are more
suitable for masonry, are less prone to "bleed through" or
discoloration when applied over asphalt and are generally easier to
spray as they don't change viscosity significantly at different
temperatures.
Q:
What are reflectivity and emissivity and why are they important?
A:
reflectivity is the percentage of solar energy reflected by the
coating back into the atmosphere. The remaining energy that is
absorbed increases the temperature of the roof surface. Higher
reflectivity results in less absorbed energy which results in less
potential heat gain.
Emissivity is
a measure of the coatings ability to emit absorbed solar energy as
infrared radiation. higher emissivity will generally result in a
cooler surface for two materials with the same reflectivity. The
relationship between emissivity and roof temperature is complicated by
factors such as conductivity of the roof surface and wind speed that
will allow some lower emissivity surfaces to shed heat energy more
efficiently.
Q:
What type of coating is more energy efficient, black, aluminum or
white?
A: The answer
depends upon climate and the percentage of energy used heating and
cooling a structure. In hot climates white is most efficient, in
temperate climates aluminum coatings with high reflectivity and lower
emissivity yield the best result. In extreme Northern regions
dark colored roofs will save the most energy as air-conditioning is
uncommon.
Q:
What Lucas brand products are equivalent to the Henry or Karnak brand
products?
A: Our
recommended Lucas equivalents to Karnak & Henry brand products are
listed on the following table: Off-sets
Q: What’s the difference between asphalt
and coal tar?
A: Asphalt is derived from crude petroleum. It’s an aliphatic or
‘straight-chain’ hydrocarbon resin. Coal tar is derived from the
destructive distillation or coal. It is an aromatic ‘ring shaped’
hydrocarbon resin. The two are different and generally incompatible.
Asphalt is normally lower in cost, can be used on pitched roofs to
vertical, has fair resistance to UV degradation and can be left bare
or surfaced in a variety of manners, but it has poor resistance to ‘ponding’
water. Coal Tar can only be used on near to dead level roofs and has
poor resistance to UV degradation so it must always be surfaced with a
layer of gravel, pavers or vegitation. Coal tar has good resistance to ponding water and
exhibits ‘cold flow’ or ‘self-healing’ characteristics.
Q: How do I tell the difference?
A: There are a number of indications as to the type of built up
roof. The first is that coal tar is always surfaced with gravel,
pavers or vegetation. If it,s bare, coated or surfaced with sprayed
in granules, it’s asphalt. If it is a gravel roof the simplest
method to determine the type of roof is to wipe the roof with a clean
rag soaked in mineral spirits paint thinner. Mineral spirits is an
aliphatic solvent and is only capable of dissolving asphalt, which is
aliphatic as well. Asphalt roofs will leave a black or dark brown
residue on the cloth while coal tar will leave a yellow or slightly
green residue. Several passes with a clean cloth may be necessary if the
roof is dirty.
Q: What allows wet surface roof cements to
adhere to wet or under water surfaces?
A: An oil soluble ‘surfactant’ or soap is added to the mastic.
The surfactant lowers the surface tension of the mastic and allow the
moisture present on the roof to be displaced. Pressure
will be necessary to aid in adhesion of the mastic to wet surfaces. These
surfactants also promote penetration of, and adhesion to, polyester
reinforcing fabrics.
Q: Aren’t all asphalt roof cements the
same?
No, some manufacturers add large amounts of filler, reclaimed fuel
oil (usually listed as petroleum distillate) and even up to 20% water!
Fillers not only increase the sheer weight of the material but can
also reduce long term performance. Some commercially available roof
cements weigh in excess of 12 lbs. per gallon (60 lbs per 5 gallon
pail). In contrast, Lucas Roof Cements weigh 8.3 to 8.5 lbs. per
gallon (42 to 45 lbs. Per 5 gallon pail).
Q: What’s the difference between Lucas ‘Standard
Grade’ and ‘Premium Grade’ cements and coatings?
A: Lucas Premium Grade roof cements and coatings are manufactured
from higher softening point asphalts which causes them to cure faster,
age more slowly, and resist oxididative cracking or ‘alligatoring’.
Lucas Premium roof coatings can take roof traffic sooner and Lucas
Premium roof cements will adhere to vertical surfaces without sagging,
even when hot mopped. Lastly, Lucas Premium roof cements contain no
unnecessary fillers like limestone dust (calcium carbonate), kaolin
clay or slate flour. These fillers not only increase the sheer weight
of the material but can also reduce long term performance.
Q: How should I evaluate the relative quality
of different aluminum roof coatings?
A: Unfortunately there is no clear standard beyond the minimum
requirements of ASTM D-2824, which all Lucas Aluminum Coatings meet.
The reputation of the manufacturer is paramount. The simplest method
to sort out aluminum coating is by aluminum pigment content. Some
people object to this standard by claiming that a coating with 2 lbs.
of ground up aluminum cans would rate the same as a coating with 2
lbs. Of high quality leafing aluminum paste. For this reason we
recommend that users ensure that, when aluminum coatings are graded by
pigment weight, the aluminum paste is quoted as meeting ASTM D-941—Specification
for Leafing Aluminum Paste. Another excellent source of information is
the EPA’s Energy Star Program which lists reflectivity values of
various roofing materials.
Q: When should aluminum roof coating be
applied to a new asphalt or modified bitumen roof? As soon as possible
or after the roof has cured?
A: The best time to apply aluminum roof coating to a new built up
roof is after the roof has fully cured. This will take at least 6
weeks. Application of aluminum roof coating to uncured asphalt will
likely result in sulfur and oil bleed through and sometimes severe
cracking or splitting.
SBS modified bitumen should be coated as soon
as practical.
APP modified bitumen is the most challenging roof to coat with
aluminum roof coating. Applying the coating immediately will reduce
‘exudation’ or bleed through, but it will not be eliminated,
expect temporary discoloration. Waiting until the membrane has cured
will allow most of the exudate to bleed out. If the roof has positive
drainage the exudate will wash off the roof and the modified bitumen
will present a clean and stable substrate. Roofs with ‘bird baths’
may retain exuded oil and sulfur compounds in low areas. This retained
contamination will interfere with adhesion, discolor the coating and
can cause the coating to crack. This contamination should be removed
with a suitable power washer and detergent. It is the prerogative of
the roofing contractor to examine the conditions present on a
particular roof and choose the appropriate action. If there is any
doubt please contact our technical personnel.
Q: Are all ‘rubberized' roof cements ‘elastomeric'?
A: Not necessarily. Rubberized means that ‘rubber’ has been added
to the mix. Elastomeric implies that the material has the rubber like
properties of elongation and recovery. Some ‘rubbers’ such as butyl,
neoprene and SBR will not impart elastomeric qualities on an asphalt
mixture. ‘Rubbers’ such as SBS and SEBS will, but only if added in
sufficient quantities to an asphalt that is suitable and not overly
corrupted with economizing fillers.
Q: What is the difference between ‘waterproofing’
and ‘damproofing'?
A: Damproofing will resist penetration of moisture through a
foundation into the interior under normal conditions. Waterproofing will
do the same even in the presence of hydrostatic pressure.
Q: What are the advantages and disadvantages of
applying coatings by brush, roller and spray?
A: Brush application allows the coating to be ‘worked in’ to the
surface. This will ensure an adequate bond, particularly if the surface
is less than ideally clean and smooth. Brush application is the most
time consuming method and will often result in visible brush marks.
Rollers are faster than brushes and still allow a measure of
mechanical assistance in adhesion to the surface. Rollers also eliminate
brush marks but may still leave a textured surface. Applicators should
be aware that rollers will lower the natural rate of coverage below that
which is recommended.
Spray application is the fastest method of coatings application and
generally leaves the smoothest surface. Total lack of mechanical
assistance in adhesion, difficulty in assessing coverage rates and the
danger of ‘over-spray’ limit the suitability spray applications.
