What Causes Seasonal Expansion and Contraction?
The cause of seasonal expansion and contraction of building materials is changes in temperature and humidity throughout the year. In winter, cold outdoor temperatures combined with dry indoor air from heating systems lead wood framing to shrink and contract. The opposite effect occurs in summer — hot outdoor temperatures plus humidity from air conditioning systems cause wood framing to expand.
This expansion and contraction of wood framing are most noticeable along drywall seams and at connections between walls and ceilings. As wood shrinks in winter, gaps open up along seams. Then, as wood swells in summer, the separated seams close back up.
Effect on Drywall Seams
The seasonal movement of wood framing places stress on drywall seams and joints. As wood framing contracts in winter, drywall tape can tear loose. Gaps then appear between drywall sheets and where walls meet ceilings.
These gaps are typically wider along interior walls than exterior perimeter walls. That’s because interior walls aren’t insulated, allowing more heat to escape into the colder attic space and increasing moisture condensation on framing members. Exterior insulated walls experience less dramatic temperature and moisture swings.
Gaps along drywall seams tend to be more pronounced on upper floors. Attics are more exposed to outdoor conditions compared to crawlspaces under ground-level floors. More moisture accumulation occurs in attic framing members. Upper-floor ceilings experience more significant expansion and contraction forces from attic framing movements.
Solutions for Managing Expansion and Contraction
There are several effective solutions for minimizing seasonal expansion and contraction of wood framing and the resulting drywall cracks:
- Apply flexible sealant — caulk gaps with a paintable sealant accommodating expansion/contraction.
- Fasten drywall tightly — screws spaced at six inches ensure drywall stays tight to framing.
- Improve attic ventilation — add more intake and exhaust vents to moderate temperature and moisture.
- Insulate interior walls — this also limits temperature and moisture changes in framing members.
- Seal air leaks — caulk and weatherstrip to reduce warm interior air from reaching cold attic framing.
- Upgrade attic insulation — better insulation reduces condensation by limiting heat loss.
- Use resilient channels — these channels decouple drywall from framing movements.
- Wait for stabilization — new construction experiences the most expansion and contraction as wood dries out.
Attic Ventilation Strategies
Properly ventilating your attic is one of the most effective ways to minimize seasonal wood movement and prevent drywall cracks. The key is controlling temperature and moisture levels through sufficient intake and exhaust ventilation.
Adding more intake vents at the eaves or soffits is one example of an effective attic ventilation technique. The ideal amount is one square foot of intake venting for every 150 square feet of attic floor space. You may also benefit from installing additional exhaust vents on the roof, such as on ridge vents, gable vents, or wind turbines.
Make sure exhaust vents are balanced evenly with the amount of intake ventilation. Remove any barriers or insulation blocking airflow from soffit vents to ridge vents. If you have any exhaust fans venting into the attic space, run exhaust vents to the exterior instead.
Properly designed attic ventilation moderates temperature swings and allows moisture to escape rather than accumulate on wood framing, reducing seasonal expansion and contraction forces. If you’re new to a home with an attic and unfamiliar with how it works, check out the basics of attics to learn how to keep your attic in tip-top shape.
Insulation Recommendations
Upgrading insulation is another effective technique for minimizing wood movement. Here are some helpful insulation strategies:
- Add insulation to meet the latest code minimum R-value for your climate zone — typically R-30 to R-38 for attic insulation.
- Make sure insulation is distributed evenly without gaps or voids.
- Extend insulation fully over the exterior top plates of the interior and exterior walls.
- Install an insulating seal or foam between exterior wall top plates and drywall.
- Insulate interior partition walls and knee walls bordering attic spaces.
- Install insulation baffles to maintain airflow from soffit vents to exhaust vents.
Proper insulation limits heat loss from the home interior through ceilings and walls into cold attics, reducing condensation buildup in attic framing and the resulting seasonal wood expansions and contractions.
Effect on Energy Bills
The gaps that open up along drywall seams due to wood contraction can allow additional cold air leakage into your home, increasing your energy bills in winter. Properly sealing cracks can improve your home’s energy efficiency. Adequately sealing windows, doors, and trim is also vital.
So, Is Controlling Seasonal Expansion and Contraction Difficult?
Managing seasonal expansion and contraction of wood framing requires careful attention to moisture control and preventing heat transfer into attics. While challenging in existing homes, choices on venting and insulation made during the construction of new homes allow for easier integration. With careful design and material selection, you can limit wood movement enough to avoid drywall cracks from expansion and contraction. This may involve choices such as using plywood structural panels, selecting laminated beams, or installing channels behind drywall.
While it’s difficult to eliminate seasonal expansion and contraction of wood framing completely, you can take steps to reduce them. Make sure to install proper attic ventilation and insulation and seal air leaks to moderate moisture accumulation in attics.
FAQs About Controlling Seasonal Home Expansion and Contraction
How much of a gap between walls and ceiling from expansion and contraction is acceptable?
Up to 1/16 inch of separation is common. If gaps exceed 1/8 inch, it likely indicates a moisture or insulation issue that needs to be addressed.
How often should caulk be reapplied to seal gaps from expansion and contraction?
Inspect caulk annually, preferably before winter sets in and gaps are at their widest. Reseal any cracks between 1/16 inch and 1/8 inch to maintain air sealing.
Will installing soffit vents help reduce expansion and contraction?
Yes, adding soffit vents can improve attic ventilation and moisture control. Just be sure they are clear of any insulation.
Does vinyl siding help prevent expansion contraction drywall cracks?
Not really. Vinyl siding limits moisture from the exterior, but attic conditions are the primary factor affecting expansion and contraction.
Should I use nails or screws when re-securing drywall that shifted from expansion?
Screws provide a more secure fastening of drywall to framing. When re-securing drywall, make sure to hit the framing members.
