CODE COMPLIANCE
GAPPING AND O V E R H A N G
Joist Spanning for Decking Trex decking meets all applicable national model building codes. The joists must be spaced on center according to the chart below. Be sure that joists are level and plumb. Trex decking must span at least three joists. For heavy items such as hot tubs, planters, etc., consult a local building engineer or inspector for span recommendations. If you want to minimize the appearance of joists through the spaces between
ADJUST JOIST SPANNING TO ACCOMMODATE ANGLED DECKING PATTERNS
You must gap Trex decking both end-to-end and width- to-width. Gapping is necessary for drainage and the slight thermal expansion and contraction of Trex decking boards. Gapping also allows for shrinkage of the wood joist system. » ALWAYS follow Trex-recommended gapping guidelines. » M aximum allowable perpendicular overhang for all Trex decking is 3/4 " (19 mm). » A ll decks require air circulation to keep them dry and looking good. To improve air flow, leave .openings under the decking or increase gapping to 3/8 " (10 mm).
3/16" (5 mm)
60°
90°
boards, paint the top of your joists black. For a Safety Data Sheets (SDS), please visit www.trex.com.
Width-to-Width The minimum required width-to-width gapping is
At a 60° angle, maximum joist spanning is 2 " (51 mm) less than listed in the chart below.
Perpendicular to joists. See chart below.
3/16 " (5 mm). This is allowed for both hot and cold weather installations. For docks and heavily wooded areas, Trex recommends a 3/8 " (10 mm) gap. No gapping should ever exceed 1/2 " (13 mm).
WIDTH-TO-WIDTH GAP WIDTH-TO-WIDTH GAP
3/16 " (5 mm)
30°
45°
1/8 " – 3/16 " (3 mm – 5 mm) 1/8" – 3/16" (3 mm – 5 mm)
END-TO-END/END-TO-WIDTH AND ABUTTING GAP
End-to-End/ End-to-Width
At a 45° angle, maximum joist spanning is 4 " (102 mm) less than listed in the chart below.
Abutting Gap
At a 30° angle, maximum joist spanning is 1/2 of the distance listed in the chart below.
Above 40°F* (4.5°C)*
1/8 " (3 mm)
1/4 " (6 mm)
Below 40°F* (4.5°C)*
3/16 " (5 mm)
1/2 " (13 mm)
*Temperature at installation.
TREX DECKING SPAN CHART (ON CENTER) Residential Decks, Light Duty Docks, Residential/Day Care Playground
End-to-End/End-to-Width Gap Trex decking end-to-end, based upon the temperature at
Commercial Decks, Boardwalks and Marinas
W hen you use the recommended hidden fasteners, the placement of the hidden fastener establishes the designated gap size. .When installing fascia, gapping rules must apply.
installation. See chart at left. For fastening tips, see page 11.
Decking Loading 1" (25 mm) Boards
100 psf = 4.8 kN/m2
100 psf = 4.8 kN/m2 200 psf = 9.5 kN/m2
16 " (406 mm)
12 " (305 mm)
16" (406 mm)
1/4" – 1/2" (6 mm – 13 mm)
Abutting Solid Objects When decking is abutting a wall, you must also gap it 1/4"–1/2" (6–13 mm) depending on the temperature at installation. See chart to the left.
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