8/9/2019 Installation instructions for Underdecking (metric)

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HOW TO

INSTALL

UNDERDECK 

1. SETTING PITCH LINE AND POSITIONING JOIST RAILSBefore installing Underdeck double check t hat your deck is level. This will allow you to correctly set the pitch lines ensuring that the water will drain

away from the home. Begin where deck connects to the home, at the ledger board. Place a mark on side of joist 25mm up for every 3 m of joist length

(approximately 3mm per 300mm of joist length) - no higher than 45mm from bottom edge of joist. Move to outside of deck (rim joist) and snap a

chalk line from the bottom of t he joist, up to the mark t hat establishes the pitch at the house end of the joist. Repeat this step on both sides of all

main joists and only on the inside of the edge joists (boundary gutters).

2. ATTACH UNDERDECK FLASHING

Attach Underdeck flashing on all sides of the deck that are connected to the structure. Underdecks water diverters or flashing should be installed at

the ledger board between each joist to ensure water run-off at ledger. Place a bead of w aterproof caulk along top edge where water diverter meets

the joist.

3. LOCATING AND ATTACHING JOIST RAILS (Important: install Underdeck wa ter diverters/vinyl flashing at ledger board first.) 

Starting 25mm from ledger board (at home end of deck), position the bottom of the joist rail along the existing chalk line. Attach both ends of t he rail

in place using approved fasteners (stainless steel). Each joist rail requires at least three fasteners (do not over drive the head of the fastener, leave

little room for movement). Locate and fasten each successive rail along the same line, maintaining a 38mm minimum to 50mm maximum space

between the rails for drainage. Repeat this step on both sides of all main joists and only on t he inside of the edge joists (boundary gutters). Joist rails

can be cut at the end of the joist to maintain the appropriate spacing.4. INSTALLING COLLECTOR PANEL

Measure the joist length of the joist space and cut c ollector panels 6mm shorter than the measurement to allow for expansion. The textured side of 

the collector panel should be facing down. Where the deck attaches to the home, insert one long edge of the collector panel between upper and

lower flanges of the joist rails. Gently push the other side of panel into joist rails on the opposite side of joist space. Work your way to other end of 

 joist space. For joist space widths other than 400 mm on cent er, see chart below. Warning: Do not allow panels to flatten out. A consistent arch is

necessary for strength and drainage.

5. ATTACHING JOIST GUTTERS

Measure the joist length and cut the joist gutter 1/4" s horter than the measurement to allow for expansion. (If joists rest on a dropped beam, cut the

 joist gutter 38m m shorter than the distance from ledger board to the beam.) Hold the joist gutter up to bottom of the joist, spread open slightly while

pushing up firmly until gutter snaps into t he joist rail and nests tightly against the collector panel. Squeeze the sides of gutter to ensure a tight fit in

the joist rail slots. Work your way to the end of the deck. *Recommendation: Before installing the joist gutters and boundary gutters, apply 125m m

pieces of UnderDeck adhesive-backed foam weather-stripping to the gutter. Affix the f oam rubber to the inside edge of joist gutter at the home end

only to form a water dam. Place a bead of acrylic caulk on the inside corner of the gutter where the foam rubber and gutter meet.

6. ATTACHING BOUNDARY GUTTERS

Boundary gutters are used on the two edge joists at the two outer edges of the deck. The boundary gutter is installed by sliding the back wall of t he

boundary gutter behind the joist rails, pushing firmly upward until gutter rib locks into the rib on the back of the joist rails. Work your way to the end

of the deck. When t he edge joist (boundary gutter) is attached to the building, it is important to install Underdeck vinyl flashing 100 -125m m above

the joist rails along edge joist. This will divert water onto the collector panel and not allow water to drip behind the joist rails and the boundary

gutter. (please see recommendation in STEP 5 before installing boundary gutters).

WORKING AROUND A BEAM

Some decks have a support beam running perpendicular to the joists at a distance from the home. I n such cases joist rails and collector panels can

continue to run over the beam. H owever, the joist gutters must end at the beam. Stop the gutters 38mm short of beam to allow f or drainage. Mount

a standard conventional rain gutter (not provided) along the full length of the beam to ca tch water emerging from t he Underdeck joist gutters. This

gutter should be pitched in one direction and can be installed with a dow nspout at corner post. On the other side of the beam, begin a new set of 

 joist gutters following the same procedure as outlined in STEP 1-6 above. Continue to the end of the deck joist.

COLLECTOR PANEL WIDTH CHART 

Joist Space

0 to 76mm

79mm to 266mm

270mm to 368mm

370mm to 457mm

460mm to 571mm

575mm or Wider

Collector Panel Width

Call for Special Conditions

Same as joist space

127mm Wider than joist

space

25mm Wider than joist space

38mm Wider than joist space

Call for Special Conditions

Tape measure Gloves

Chalk Line Safety glasses

Step Ladder Hammer or Screw Gun

Water Diverters Vinyl flashing

25mm or 28m m hot-dipped galvanized roofing nails or

pan head screws (3-4 p er rail)

Before Underdeck After Underdeck

8/9/2019 Installation instructions for Underdecking (metric)

http://slidepdf.com/reader/full/installation-instructions-for-underdecking-metric 2/2

HOW TO

INSTALL

UNDERDECK 

PRO SERIES INSTALLATION INSTRUCTIONSUNDERDECK CAN BE INSTALLED ON VIRTUALLY ANY SIZED DECK 

USE CHART BELOW TO DETERMINE MATERIALS REQUIRED

Product compatible with 12, 16 and 24 on-centre joist spacing. Available

on a special orders basis

WHAT YOU WILL NEED **MEASURE JOIST LENGTH IN LINEAL FEET**

914mm Long

JOIST RAILS 

Number of joist spaces _____ x length of joist in mm ______ x 2 ÷ 37 = ______ number of joist rails

(3 m = 3000mm 3.6 m = 3600mm 4.2 m = 4200mm 4.8 m = 4800mm)

3, 3.6, 4.2, 4.8 meter

lengths

COLLECTOR PANELS 304mm on-centre 406m on-centre 609mm on-centre

Number of joist spaces _________ = number of collector panels

Length of joist in meters ________ = length of collector panels

3.0, 3.6, 4.2, 4.8

meter lengths

JOIST GUTTERS 

Number of inside joists _________ = number of joist gutters

Length of joist in meters ________ = length of joist gutters

3.0, 3.6, 4.2, 4.8

meter lengths

BOUNDARY GUTTERS 

Number of outside joists _________ = number of boundary gutters (typically 2)

Length of outside/edge joist in meters ________ = length of boundary gutters

3.6, 4.8, 7.3

meter lengths

WATER DIVERTERS 304mm on-centre 406m on-centre 609mm on-centre

Number of joist spaces _________ = number of water diverters

127mm strips

FOAM WEATHER STRIPS 

Number of joist gutters _________ = num ber of foam weather strips

Number of boundary gutters _________ = number of foam weather strips

Before Underdeck After Underdeck