Wood Sheathing Panels
If you have ever seen a roof or a wood panel that has areas that look ‘swollen’ as if an air bubble has formed beneath it, you’d know that it is an aesthetic disaster.
It’s called buckling and is a common occurrence in Plywood and oriented strand board (OSB) roofs and panels.
Buckling occurs due to moisture condensation in the attic. This moisture is absorbed by the wood sheathing panels until there is an equilibrium with the new surrounding environment. When it absorbs moisture, wood expands and without space to expand, it starts to buckle.
If you are building a new home or are redesigning your existing one, then your building contractor and building supplies company should consider a few simple tips recommended by the APA (American Plywood Association) that will help avoid buckling.
There are two ways to tackle this problem.
Panel spacing is the easiest way when you are building a new home. It is recommended by the APA that there must be a gap of at least 1/8 inch between panels. Contractors generally use a #10 penny box nail as a rule of thumb while installing OSB or plywood panels. This space allows the panels to expand or contract without causing buckling. Your building supplies manufacturer can shed more light on this.
Speak to your contractor to ensure that the panels are installed according to local building codes. Wall framings must also be level as improper framing techniques can also cause buckling.
The other way is to let the wooden panels acclimatize to their new environment before installing them. Having said that, you must ensure that if the panels are stored on site during the construction process, you cover them to prevent them from getting wet. If the panels are exposed to moisture, they will expand more rapidly.
Repairing without removing the roof
The above mentioned techniques will only apply if you are installing the roof. How do you prevent buckling without uninstalling the roof?
To control moisture in attics and crawl spaces, you must check the ventilation. Any adequately ventilated space will not have moisture build up as it allows the damp and moldy air to move out. It is recommended that the adequate ventilation without the installation of a vapor barrier is 1 sq foot for almost 150 sq ft of attic space.
Check if your blocking or bridging interferes with the movement of air in these spaces.
Check the vents in your attic and soffit. Install baffling to ensure that the vent openings are not clogged by the insulation. Fixtures should be sealed correctly.
If you are venting appliances into the attic or crawl spaces, change it to the outside. A licensed roofing contractor will be able to make the apt suggestions after checking your attic space.
With effective moisture control, you can prevent buckling in the wood sheathing panels easily.
For existing panels that are warped, the following techniques can be used:
- Saw-cut the ends of structural panels. This helps relieve pressure and also creates a gap that allows the panels space to expand in future
- The buckled areas can be strengthened with wood blocking.
- A panel clip can be used to level and align the buckled panels