Cracking Over
Caulk
Cause
When paint is applied over a partially dried bead of
caulk, the paint dries, first forming a film. As the caulk continues to dry, it separates
from the underside of the paint film. Ultimately, the paint film cracks.
Conditions that affect the drying time for caulks
are air, surface or caulk temperatures below 40F; high humidity; and joints in excess of
1/2'' in width or depth.
Solution
Surfaces to be sealed should be sound, dry, and free
of oils, dust, mortar spatter, release agents, old caulk, bitumen, old paint or other
contaminants. Remove flaky, loose, and powdery material from the joint.
Apply caulk only when temperature of surrounding
air, surfaces to be caulked, and caulk are all above 40F. Do not apply when rain or
freezing temperatures are expected. Joints should not be more than 1/2" in width or
depth. Joints deeper than 1/2'' should be filled within 1/2" of the surface with
polyethylene rod or closed cell urethane foam. Fill the remaining joint with caulk, and
tool within 5 minutes of application.
Recommended Sherwin-Williams Coating System
One coat A-100 Latex or Alkyd Exterior Wood Primer
Two coats Exterior Latex House and Trim Paint.
Plywood Cracking
Cause
Plywood cracks from its expansion and contraction
with changing moisture content. Plywood is prone to cracking because of its original
method of manufacture involving peeling thin sheets of wood from logs. Stresses are
induced which later show up as cracking. Many small fissures are produced in films of
paints and stains that have been applied to insufficiently dry plywood. The edges of these
cracks protrude upward and can be felt as sharp burrs. Subsequently, this coating my
become detached from the edges of the cracks and lead to flaking.
Solution
New wood: To prevent cracking of newly installed
plywood, sand and prime with Sherwin-Williams Latex Exterior Wood Primer.
Repaint: If cracking is severe, replace the wood,
for this is an unpaintable surface.
If the cracking is not extensive, sand surface
smooth. The plywood must be thoroughly dry. Apply latex primer.
Recommended Sherwin-Williams Coating System
-New Wood
One coat A-100 Latex Exterior Wood Primer
Two coats Exterior Latex House and Trim Paint
-Repaint
Spot prime with A-100 Latex Exterior Wood Primer
Two coats Exterior Latex House and Trim Paint
Darkening
and Decaying of Wood
Cause
Darkening of wood is caused by ultraviolet
radiation. This can take place in wood that has never been coated with a protective
coating. It can also occur under clear varnishes and lightly pigmented stains. Different
degrees of darkening can occur on different woods. If moisture is penetrates into the
wood, varnish coatings will peel due to wood decomposition under the coating. Woods that
are exposed to weather are not protected against wood-destroying organisms. Eventually the
wood ceases to be a coatable surface.
Solution
New woods must not be exposed to harmful sun rays
for extended time periods. Paint and stain adhesion performance is enhanced when the new
wood is painted or stained immediately after installation. Wood that has been allowed to
darken (decompose) must be sanded to fresh wood. Wood that cannot be sanded to fresh wood
must be replaced.
Coatings can be applied to treated woods after the
moisture content has dropped to a paintable level. Semi-transparent stains must be used on
all horizontal (walk-on) surfaces. Paints, semi-transparent and solid color stains can be
used on vertical surfaces.
Recommended Sherwin-Williams Coating System
Two coats WoodScapes Exterior Acrylic Solid Color
Stain or
One coat A-100 Alkyd Exterior Wood Primer
Two coats Exterior Latex House and Trim paint (Flat,
Stain, or Gloss)
-Decks and porches
Cuprinol Deck Care Products
Under-Eave
Peeling
Cause
Lack of inter-coat adhesion can occur if:
Paints are applied to old hard and glossy paint
films.
Salts which were formed during the life of the
previous coat were not removed before the new coat of paint was applied. These salts form
an invisible film preventing a bond with a new topcoat. This leads to loss of adhesion and
peeling.
Solution
Sand surface and wash all protected areas with a
strong detergent solution and water. Rinse thoroughly with clean water and allow to dry.
Recommended Sherwin Williams Coating System
One coat A-100 Alkyd Exterior Wood Primer
