Installation Guide

22
Condition
IN-PLACE CONDITIONS (cont.)
Joint Ridging Or Beading
Most commonly occurring
when steel studs (24" on center)
are used and rapid drying
conditions exist
Rusting/Staining Of Finish
Photographing Or Ghosting
Of Joint Line
Joint Shadowing Caused By
Depression Or Ridging
Bond Failure
Cause(s) of bond failure is
perhaps the most difficult
condition to diagnose because
of the great number of factors
which can influence plaster
bonding
Probable Cause
1. Large gaps between adjacent
plaster base boards.
2. Improper/insufficient number/
location of fasteners.
3. Gypsum base board edges damaged.
4. Wrong type or no reinforcing
mesh used.
5. Joints not pre-treated prior to
general plastering.
6. Rapid drying conditions.
Use of improper fasteners or metal
trim.
1. Differential in base plaster suction
between joint and field.
2. Too thin a coat of base plaster
overall, resulting in a very thin
covering over mesh.
3. Partially dry base plaster, mois-
ture content differential greater
between joint and field.
Gypsum veneer base gapped
causing a depression or ridge at
the joint line.
Product Related Causes:
1. Use of pressure sensitive mesh –
reduces plaster substrate contact.
2. “Setting” or “drying” type joint
compounds used to treat joints.
Job Condition Causes:
1. “Dry-out” or “partial dry-out”
– plaster loses water prior to
complete setting or hydration.
2. Using plaster which has been
exposed to the atmosphere,
open bags or improper storage.
3. Freezing of plaster before setting
has occurred.
4. Application of plaster over frost
on substrate.
5. Excessively rapid thermal changes.
6. Excessive thermal differences
between the face and back of
the plaster base.
Application Practice Causes:
1. Application of lime containing plas-
ter over light faded veneer base.
2. Use of retempered plaster,
remixing with additional water
plaster which has “bucked-up”
(stiffened) or started to set to
render it workable again.
3. Excessive delay in applying plaster
after mixing – application near
or into the initial setting action.
Preventive Action
1–3. Apply undamaged plaster
base board according to
recommended procedures using
proper fastening.
4/5. Use recommended
reinforcing mesh or paper tape
and pretreat joints prior to gen-
eral plastering.
6. Avoid rapid drying conditions.
Use only recommended fasteners
and trim.
Apply basecoat plaster to full
thickness, following recommended
procedures.
Follow recommended veneer base
and plaster application procedures.
The best advice for preventing
veneer plaster problems is to strictly
follow the manufacturer’s recom-
mendations and adhere to proper
plastering practices.
Corrective Action
Sand the ridge or bead and apply
ready mixed compound and feather
out areas.
Prime affected area with a primer/
sealer and redecorate.
Prime affected area with a primer/
sealer and redecorate.
Fill depression with joint compound or
sand ridges flush with field, skim coat
with joint compound and redecorate.
Remove all loose or marginally
bonded plaster, brush the surface
thoroughly to remove dust (vacu-
uming is recommended), apply a
quality bonding agent per manu-
facturer’s recommendations and
replaster.