Installation Guide

Page 5
Expansion and Contraction
AZEK Deck/Rim Joist Covers will have expansion and contraction with changes in temperature, unlike wood whose size
will fluctuate with moisture changes. The expansion and contraction encountered may result in slight gaps, which might
be noticed at the ends of boards or in splice joints. Fastening the deck boards according to the Installation Guidelines will
help minimize expansion and contraction.
• Expansion/contraction is most significant where extreme temperature change may exist.
• Best practice is to cut and fasten the deck boards as soon after cutting as possible.
• For better results keep decking as cool as possible during attachment. Direct full sun exposure will increase board
temperature and length. If attaching during high heat, larger gapping can be expected. Be sure to keep butt joints
tight. Do not leave a gap at butt joints, splices or miters.
• Be sure to fasten ends of boards, splices, or abutments to building or structure securely into framing using 2
screws. Position the screws at or within 1/2” of each board end or joint and 3/4” from side of deck plank.
• For butt joints, be sure to trim cut factory ends to ensure squareness. Do not scarf cut butt joints.
• Provide a 1/8” to 1/4” side to side gap between deck boards.
• In areas with obstructed airflow such as roofs and on-grade applications, a minimum of 1-1/2” sleeper system
supported by and connected to the substructure over which the deck is built is required.
• Framing/sub-structure must be securely attached to ground footings or building structure. No floating sub-
structures should be used in any application with AZEK Deck, including on grade, concrete, or in roof top
applications.
• For best results, stagger splices and miters across deck surface so that all splices and miters do not break on the
same joist or beam.
• To further minimize expansion and contraction, proper ventilation and air flow should be considered.
• Some area building codes may require double joisting when joining boards end to end. Double joist and/or secure
double blocking is always required at butt joints when using ConceaLoc or FusionLoc fasteners. Always check with
your local code authority for specific requirements before installation.
• During installation, frequently check that AZEK Deck boards are installed straight and with consistent gapping and
spacing by using a string line.
3/4”
1/2”
Fasteners
• Due to the durability of AZEK deck products, a high-quality fastener is recommended that meets the following
specifications:
• Stainless Steel
• Minimum Screw Size: #7
• Face screws to be a minimum length of 2 1/4”
• Be sure that screws are driven to a minimum depth of 1 1/4” into solid wood framing below the bottom of the AZEK
Deck Board. This will enhance holding power and uplift resistance.
• Avoid using flathead screws. Trim head screws typically provide a better result. As always, you should try the
fastener in a sample board before using on your deck.
• Be sure to install 2 screws per joist on each deck board. regardless of temperature during attachment of AZEK
deck boards, be sure to keep butt joints and miters tight and place fasteners within 1/2” of ends.
• For salt water coastal applications, we suggest using the above minimum fastener requirements in 316 stainless
steel.
Working with TimberTech AZEK
®
Deck Boards