Friday, November 1, 2013

Drywall Cracks and Nail Pops in your Home

In North America, we have an abundance of wood (thanks to the fact it grows on trees) which has proven to be an excellent building material over many centuries. It is however an organic-cellular product which will swell with too much water or shrink when dried out. This cycle of expansion and contraction can happen seasonally and it also typically happens with ‘new’ wood that is used in construction and is part of the original ‘settlement’ of the home.
The downside of this regular seasonal movement is some common cosmetic damages in the home can occur, and in some cases, can be misdiagnosed.

Seasonal Drywall Cracking
When the wood framing in our walls expands and contracts with temperature and humidity, it puts a slight amount of stress on the materials attached to it, principally for interiors, the drywall sheet rock. Drywall is a non-organic material that does not have the same expansion and contraction rates at the wood supports it is attached to. This can lead to small stress fractures occurring at the weak points in the drywall system, typically where the drywall has joints, or where there are weak points in the system like above doors and windows.

In a typical home, the drywall to wood connection is about 8’ from the floor to the ceiling, however, the taller the wood structure, the more movement the rest of the building needs to absorb. This mean top floor condo’s in a 4-story wood building tend to see more stress fractures as the entire building moves more but even in standard 2 story homes, where two-story openings exist (thereby creating a 19’ ceiling), the drywall is more likely to crack. The last thought on this two-story phenomenon is where a normal 8’ ceilings transition to a 19’ ceiling, it is not uncommon for the difference in material expansions to create stress cracks in this location too.

Building Settlement and Nail Pops
Wood used in construction is what is called ‘green lumber’ or ‘new’ wood. This wood has been relatively freshly cut and still contains a lot of moisture retained by the original tree. ‘Green lumber’ wood may contain up to 19% humidity. Over the first few years after construction, the moisture in the wood will dry as it is now sheltered from the environment and no longer fed new moisture by the trees circulatory system. Wood will settle typically between 8-12% after the first few years.

In the process of losing this moisture, the wood will shrink. How much it shrinks will be based on which direction the fibers of the wood are in but wood studs can shrink up to 1/2 of 1% or 0.5% of their height and more in their width and breadth. So for a common 8-foot wall, the wall will actually shrink up to 1/2 an inch in the first few years. On a two-story home, this can be up to about an inch of settlement. Lastly, if you live on the 4th floor of a wood framed condo, your view will shrink about 2” from when you first move in.

The effect of this shrinkage is similar to seasonal cracking. Drywall materials which are not shrinking will become compressed and stress fractures will occur at weak points in the system. Unlike seasonal cracking though, this original building ’settlement’ will happen once and then can be repaired and painted not to happen again, unless of course it is combined with seasonal cracking.

Nail Pops
As the wood shrinks, another cosmetic flaw that can happen are nail pops. Sheetrock contractors often use drywall nails to quickly tack drywall into place during construction. Unfortunately, as the wood behind the drywall shrinks, the nails don’t and in some cases the wood will shrink away from the nail leaving the nail head sitting proud off the surface of the wall or ceiling. Fixing these after the buildings original settlement is usually a permanent solution to the cosmetic flaw.

As a SitePro inspector, I would love to see the drywall industry only use drywall screws as they are less likely to cause future cosmetic problems.

Final Thoughts
As a SitePro Inspector, I am at a disadvantage when I see a crack in drywall. A crack in drywall could be caused by:

  • ·         Normal seasonal movement (meaning unless the client plans to fix and paint every year, the flaw will constantly re-appear)
  • ·         Original building settlement (which if not fixed could still be visible many years after constriction)\
  • ·         Other building structural issues which may be a bigger concern to the client

This disadvantage means that I will typically report on the presence of cracking but I won’t be able to diagnose the cause without observing the crack for a longer time period, perhaps 1-2 years. As a home inspection lasts 2-4 hours, it is not possible to give clients a definitive answer on a crack in drywall.

A SitePro inspection is designed to lessen the risk to home buyers, but we cannot eliminate all risks. Home buyers should always be aware of any cracks in their home and observe them regularly for changes which may indicate larger problems.
Van Hibberts, CMI

Certified Residential Building Code Inspector ICC-5319905
Florida-State Certified Master Home Inspector Lic. #HI 89
Certified Owens-Corning Roof Data Technician
Florida-Certified Wind Mitigation Inspector
WDO Certificate #JE190791 
InterNACHI #10071802
362 Gulf Breeze Parkway, #214
Gulf Breeze, Florida 32561
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