Basic cautions – USG Manufactured Housing Handbook User Manual

Page 26

Basic Cautions

– The hardening action of setting-

type joint compounds cannot be
delayed or prevented by dilution
with water.

– Joint compounds and textures

should not be applied over moist
surfaces or surfaces likely to
become moist, on below-grade
surfaces, or on surfaces projecting
to the outside of the structure,
unless protected from direct expo-
sure to moisture.

– S

HEETROCK

MH Brand Setting-Type

Joint Compound (T

-S

) is very

difficult to sand smooth after dry-
ing. Smooth it before it hardens, or
while it is in a hardened but still-
damp state. Where better sanding
ability is required, use S

HEETROCK

MH Brand Lightweight Setting-
Type Joint Compound (T

-S

Lite).

– Water-based finishes may result in

sagging of gypsum board ceilings
under these conditions: high heat
and humidity, cold damp condi-
tions, improper ventilation and/or
board application to framing, and
insufficient board thickness for
span between supports.

– All finishing materials must be dry

prior to sealing the units, or, where
required, prior to removing ventila-
tion and supplemental heat.
Failure to do this will result in
board sag, surface defects, and
weak joints.

– Excessive water dilution of texture

finishes causes check cracking,
poor bond, and lack of hide.

– Do not intermix texture finishes

with any products except those
approved by the manufacturer.

– Application of texture products

over unprimed, improperly pre-
pared, or incompletely dried sur-
faces may cause discoloration
problems.

– Unless texture finishes are applied

at the recommended coverage
rate, check cracking from exces-
sive thickness or poor hide from
too thin a coating can occur.

– When applying joint compounds

and texture finishes, maintain
minimum air, water, mix, and sur-
face temperature of 55 °F (13 °C)
until dry.

– Failure to protect stored joint com-

pounds and texture finishes from
temperature extremes, moisture,
and free water can cause material
to become unusable.

– Failure to rotate stock of joint com-

pounds and texture finishes causes
material to age. Use of aged mater-
ial may produce erratic results.

– Follow good safety and industrial

hygiene practices during handling
and installing of all products and
systems. Take necessary precau-
tions and wear the appropriate
personal protective equipment as
needed. Read material safety data
sheets and related literature on
products before specification
and/or application.

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adjust air/material mix and fluid
and air nozzles. Use proper equip-
ment and application techniques to
achieve the best results. Make sure
equipment is in good working con-
dition; replace when necessary.

Problem: Unsatisfactory pumping

properties.

Cause: Mix is too heavy; pumping

equipment is worn, or of insuffi-
cient size or power.

Prevention: Use recommended

amount of water to ensure proper
spraying consistency. Use equip-
ment recommended by the manu-
facturer that is matched for the
area to be sprayed. Make sure
equipment is in good working con-
dition; replace when necessary.

Problem: Texture buildup.
Cause: Texture applied over high

suction joint (surface not primed);
allowing too much time between
roller, brush, or spray application
and hand-texturing operation.
Overdiluted texture will produce
texture buildup over a joint.

Prevention: Prime the entire surface

with S

HEETROCK

Brand First Coat or

an interior flat latex paint having a
high solids content. Use the correct
amount of water when mixing the
texture material. In hand-texturing
operations, allow for time between
application and final texturing
steps.

Problem: Poor color match, ceiling

and sidewall.

Cause: Overspray on ceilings when

walls are sprayed with a different
texture or with paint products from
different manufacturers.

Prevention: Be careful not to allow

overspray of paint products. In all
drywall homes, paint ceilings and

walls with the same brand of finish
paint.

Finished Surface
Problem: Joint show-through.
Cause: Overthinned or inadequate

coverage with texturing material
will not hide the normal contrast
between the joint compound and
the gypsum panel surface.
Texturing over an unprimed sub-
strate can also result in joint show-
through.

Prevention: Use correct amount of

water when mixing texture material
and apply at recommended rate of
coverage until joint is concealed.
Prior to texturing, prime entire sur-
face with S

HEETROCK

Brand First

Coat or an interior flat latex paint
having a high solids content.

Problem: White joint banding over

gypsum panel substrate.

Cause: High suction joint causes a

porosity variation, which often
appears lighter in color than the
gypsum panel surface.

Remedy: Allow texture to dry com-

pletely, and paint entire surface.

Prevention: Prior to initial decorat-

ing, prime the entire surface with
S

HEETROCK

Brand First Coat or an

interior flat latex paint having a
high solids content.

Problem: Joint darkening.
Cause: Application over damp joint

compound, especially in cold,
humid conditions.

Remedy: Allow texture to dry com-

pletely, and paint entire surface.

Prevention: Allow joint treatment to

dry completely, then prime the
entire surface with S

HEETROCK

Brand First Coat or an interior flat
latex paint having a high solids
content.

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