Building a deck in a climate that sees extreme weather such as extreme heat, extreme cold, hurricanes, lots of rain, ice and snow requires some extra planning to ensure your deck will last and resist unwanted movement such as warping, cupping, bowing and twisting.
In dry climates like Arizona, wood decking materials will shrink due to the lack of moisture. All building materials will expand and contract with temperature and humidity changes. Composite decking materials generally expand in the warm temperatures and shrink in the cooler temperatures.
Wet and Humid Climates
Climates like Florida that see extreme heat, rain, humidity and hurricanes are some of the harshest environments on homes and the materials they are built with. Constant rain and humidity will cause wood decking to expand, composite materials will also tend to swell in these climates.
These climates also tend to promote the growth of mold and fungi, especially in the areas that do not see full sun all day. This can also lead to faster degrading, rot and decay of building materials.
Extreme Sun and UV Rays
Many areas such as Florida, Arizona, California and more see extreme sun and UV rays. The UV rays from the sun are one of the harshest elements that attack many materials and building materials like decking are no exception.
The UV rays will fade most materials including wood which will eventually turn gray and composites can significantly fade from their existing color that you loved originally.
Extreme Cold, Ice and Snow
If your area gets very cold and see lots of ice and snow in the winter and then hot and humid temperatures in the summer. Your deck is going to see the widest ranges of extreme conditions which means the most expansion and contraction.
All of these different climates can be harsh on building materials especially horizontal surfaces like decking. There are materials that have proven to stand up to these harsh climates better than others.
South American hardwood decking such as Ipe, Cumaru, Tigerwood, Garapa and Massaranduba have proven to last up to 75 years in some applications.
These hardwood decking species have shown to work in every climate from the dry dessert to hot and humid Florida all the way to cold and snow covered Buffalo, NY.
The most common decking size is 5/4 x 6” which will have a finished dimension of 1 inch thick and 5.5 inches wide.However just like hardwood flooring the wider your deck boards are the more likely they will be to cup.
Use Narrower and Thicker Boards
The narrower a board is the less likely it is to cup so using narrow boards such as 1×4 (finished at 3 1/2″ wide), is not only more stable but it can save you money and give a more interesting look.
Thicker boards such as 5/4 x 4 (finishes at 1” thick and 3 1/2″ wide) are also more stable then 1 x 4 (finishes at 3/4” thick and 3 1/2″ wide) it’s a quarter inch thicker and gives you more stability.
Sawn Lumber Differences
Quarter Sawn Decking:
Quarter sawn decking comes at a premium due to the labor it takes to mill each plank. To mill quarter sawn wood, each log is sawed at a radial angle into four quarters. Then each quarter is plain sawn. This method of quarter sawing does leave some waste, but much less than rift sawn lumber.
This method of sawing produces a plank where the tree’s growth rings are near, or totally perpendicular to the plank’s surface. Quarter sawn decking offers even more stability and the following benefits:
- Decreased expansion and contraction on the plank’s width
- Twisting, cupping, and warping resistance
- Ages evenly over time
- Chances of surface checking are significantly reduced
- More resistant to moisture penetration
- More character beauty with ray flecks
Are Your Project Conditions Less Than Ideal?
We recommend a minimum of 18 inches of unrestricted air flow underneath your deck. Unrestricted means plenty of air can flow underneath your deck so it’s not completely sealed off with skirting.
Closing off the underside of your deck or not allowing enough air flow will change the moisture level on the underside of your deck boards while the top surface gets air flow and heated by the sun.
This creates two different climates for your deck boards and will cause the top of the deck surface to expand and contract at a different rate then the bottom and this will lead to cupping.
That being said some homeowners have projects like boat docks and ground level decks that can not meet the ideal conditions but still want a beautiful hardwood deck.
In these cases, even though we don’t recommend it unless you can create the ideal conditions we suggest using 5/4 x 4 decking or 5/4 x 4 quarter sawn decking. You should also take as many precautions as you can to mitigate any moisture issues or differences underneath your decking.
Oiling the underside of your deck boards before installing them can also help reduce moisture absorbing into your deck boards.