For Home Inspectors
As the first line of defense for a new homeowners, home inspectors need to be as knowledgable as possible about safety and maintainence issues, so they can inform their clients.
Many home inspectors have a background in the construction feild, but if your area was hvac or electrical, you may not be as knowledgable about plaster systems as a general restoration contractor might be.
On this page I will be posting resources for the home inspector, so he can make a correct assessment when evaluating a plaster ceiling. Do you have a specific question that is not addressed here? Feel free contact us for further information.
As you scroll down, you will find the following subjects:
Observation: How to recognize a failing plaster ceiling system
Definitions: 'Failure' vs. 'Collapse'
Predictability: Can Collapse Be Predictable?
Testing: Determining Soundness of Plaster Ceiling System
Reporting: Suggestions for reporting and how to direct clients
General Info:
1. Observation:
There are a number of things that the home inspector should be aware of when examining a plaster ceiling for signs of a failing attachment system.
constructed between the dates of 1920 and 1960, depending on geography.
larger sections (typ. 4'x8') of metal or gypsum lath. To determine plaster system see
Visible Cracks and Observation from Attic
and can tell us many things. First, it can tell us what type of system was used. Small,
'step' cracks indicate smaller sections of gypsum lath, often used in the 1920's -
1940's.
Long straight-line cracks across length of ceiling or curving/circular cracks indicate
use of larger sections of gypsum or metal lath.
Indications of previous repairs that failed. Often one will see evidence that the ce
iling has been taped and mudded along these cracks, but the crack has opened back up through the repair. This usually indicates the ceiling is actively moving downward. Gently pressing upwards around the crack. If ceiling attachment is failing, you will see the crack move as you gently press upwards on either side of crack. (don't do this if the ceiling is visibly out of level. You could cause a collapse! )
Measurement from floor to ceiling at crack and at wall. If distance is shorter at the crack than at the wall, it may have 'dropped' the amount of the difference.
Observation from Attic: After moving insulation from suspected area (usually in the middle of the ceiling, you may be able to observe the amount of space between the back of the lath and the joist. Since the lath should be snugly against the joist, any distance is indicative of the amount of ceiling attachment failure.
2. Definitions:
For clairity, I will be defining the use of the terms 'failure' and 'collapse' as they relate to plaster ceiling systems as follows:
Failure: references to a ceiling attachment system that has failed, is failing or is in a state of failure, means that it is observed to be in a compromised state where the system is in the process of failing at what it was intended to do; that is, hold the ceiling securely to the joists. This is a progressive condition that if left unremediated may eventually lead to 'collapse'.
Collapse: I am referring to a ceiling or part of a ceiling that has completely fallen to the ground.
3. Predictability
Can a ceiling collapse be predictable? One can say that collapses have occured as a result of inadequate attachment, but I know of no way to predict the inevitability of collapse, or the time frame. That being said, if it is clear that a ceiling is sagging or loose, it could possibly be in danger of imminent collapse. Because of the individual and unknown variables however, predictability is a judgement call.
4. Testing
Gently press upwards around the crack. If ceiling attachment is failing, you will see the crack move or hear 'popping' as you gently press upwards on either side of crack. (don't do this if the ceiling is visibly out of level. You could cause a collapse! )
5. Reporting
After determining that the ceiling is a plaster over gypsum/metal mesh system, one could safely say that such ceilings have been known to collapse and cause property damage and that it should be inspected further for remediation by a qualified plaster restortion contractor.
Even if there are no qualifed people who understand this issue, you have notified the homeowner-to-be that there is an issue that needs to be investigated further. Whether this will exonerate you from legal liability is a question I cannot answer.
General Info:
Under-Engineered Attachment System as a Singular Cause of Failure and Collapse
The fact that plaster ceiling systems fail* and collapse* is not a new issue. However, the proposal that under-engineering (a widespread condition) is a major factor in attachment failure and ceiling collapse…often the only factor…is new.
Though plaster may collapse and break off of from ‘traditional’ wood lath and cause damage, we are primarily referring to plaster-over-gypsum lath or metal mesh ceilings, especially ones that used larger sections of gypsum lath. (I refer to these ceiling systems as ‘transitional’ ceilings because this combination of materials and techniques was employed after the time of ‘traditional’ plaster over wood lath, and before modern drywall.)
Why is this a Safety Issue?
These ceilings concern the home inspector because when they collapse, it tends to be complete, sudden and monolithic. Therein lies the safety issue. Such a collapse involves hundreds of pounds of material, in addition to insulation which may also contain asbestos. (The failure and collapse occur at the point of attachment to the joists.)
My first encounter with a ‘failing’ plaster-over-gypsum rock ceiling system was here in NC. A client called me to come and look at the ceiling in his grandmother's room. One-half of the ceiling was hanging at a 5 degree angle, leaving an 8" gap the length of the room. The ceiling attachment system (between the lath and joists), was in an advanced stage of ‘failure’.
We removed the ceiling completely and dry-walled it. ** Fortunately, the grandmother had been moved out of the room and the ceiling had not collapsed on her.
The construction was three-coat plaster-over-rock/gypsum lath. It was attached by means of a ‘clip’ system to the joists, but had weakened and relaxed over time with the weight of hundreds of pounds of plaster.
Over the years, I have seen and remediated numerous such ceilings in the ‘process of failing,’ though they had not collapsed. I have also seen various attachment systems for that 'transitional' time period; the three most common being smooth nails, angled metal clips and wires. I have observed all three methods of attachment showing signs of failure.
What Should a Home Inspector Look For?
The age of the home should be your first clue. Transitional ceilings span roughly the period from the 1920’s to the 1960’s.
One way attachment failure can be observed is to look at a ceiling from the attic side (especially towards the middle of the ceiling), moving back the insulation. There should be no space between the joists and the back of the gypsum rock. Any space there indicates the extent to which the attachment system has been compromised.
A more obvious indication of attachment failure is the presence of straight cracks, either running the length of a ceiling (the most serious safety problem) or following a zigzag pattern. Because the transitional period for plaster-over-gypsum rock spans almost 40 years and different sizes of gypsum lath were used, one sees different patterns of cracking in these ceilings, following the joints in the gypsum rock.
Rarely, a ceiling may show circular or curving cracks. This usually will be a ceiling in the later part of the transitional period and also indicates a serious condition.
Another indication of a failing attachment system is the evidence of previous ceiling repairs that did not last. This is because the plaster or drywall contractor did not understand the underlying cause of the crack and did not properly anchor the ceiling back to the joists before taping and mudding.
Signs of failure can be detected by home inspectors with a trained eye in most cases. As with any potential safety issue, recommendation should be made for further evaluation/remediation by a knowledgeable plaster repair person as these ceilings have been known to collapse.
Can Collapse Be Predicted?
Though these cracks are indications of attachment failure, one cannot predict when or if these ceilings will 'collapse'. However, the state of failure, if not remediated, is a progressive one. Given enough time, collapse is likely to eventually occur.
An early client, M. Rothrock of Greensboro, N.C., shared a story with me as I was remediating the living room ceiling in her father's home (this one was attached by wires and was about 3" away from the joists as seen from the attic side)
The neighbor's house, built at the same time in the 40's by the same contractor, experienced a total collapse of all the ceilings in the house shortly after construction. Besides a number of similar stories from clients, I have found a number of instances online of property being damaged and in one case, a small child being killed by what appears to be this type of sudden monolithic ceiling collapse.
* Estate Plaster Inc. has developed remediation techniques that do not require the removal of the ceilings in most cases. If a ceiling can be re-secured, it saves time, trouble, as well as money for a client. Proper remediation may also decrease failure and collapse due to contributing causes, such as water damage, storms or factors related to heating/cooling cycles and the affects of vibration or impact.