The finish line

A Forest Products Laboratory finishing factsheet

United States Forest Forest

Department of Service Products

Agriculture Laboratory

Construction of a Dip-Tank for Finishing Wood Siding or Decking 

Dipping new siding or decking 

pieces before installation is faster 

than finishing after installation, and 

it gets finish on the backside and 

ends of the pieces, thereby 

extending their service life. This 

method is appropriate for any 

penetrating finish, such as waterrepellent preservatives or 

semitransparent stains. It may also 

be used to pre-treat siding with 

water-repellent preservative before 

painting, which can greatly extend 

the service life of the paint.

Materials 

• 2 by 4’s or 2 by 2’s 

• 4- by 8-foot panel products 

(plywood or OSB) 

• Drywall screws (see Tips) 

• 4-mil plastic (enough for two 

layers in the tank and a covering 

for the drain board) 

Although more costly, consider 

using plywood for the tank—setting 

screw heads in OSB can be difficult, 

and exposed screw heads are likely 

to puncture the plastic. Avoid using 

plastic thicker than 4 mil—it can 

crimp and crack in the tight corners. 

Construction 

The tank should be 1 to 2 inches 

wider and about 6 inches longer 

than the siding or decking boards, 

and about 8 inches deep. 

Ideally, the bottom 2 by 4’s (or 2 by 

2’s) [A] are single pieces that run 

the entire length of the tank. If they 

are pieced together from shorter 

lengths, take care that joints in the 

2 by 4’s do not align with joints in 

the tank bottom [B] or sides [C]. 

Cut plywood (or OSB) bottom 

pieces [B] to the width of the tank, 

and screw them to the bottom 2 by 

4’s [A]. Also screw plywood side 

pieces [C] (91⁄2 inches wide for 

8-inch tank depth) to the bottom 

2 by 4’s. Screw small 2 by 4 pieces 

[D] at the ends of the tank for 

fastening the plywood end caps [E]. 

Use additional small 2 by 4 pieces 

to reinforce any joints along each 

side [C]. 

A length of 2 by 4 along the top of 

one side [C] of the tank may be 

used to fasten the drain board to the 

tank. The opposite edge of the drain 

board rests on (and should be 

attached to) saw horses. 

Line the tank with two layers of 

plastic. Stapling the plastic to the 

top edge of the tank helps to keep it 

in place. 

To make the drip racks [F], space 

screws or nails 1 to 2 inches apart 

along two 2 by 4’s; test the spacing 

before going too far. After covering 

the drain board with plastic, clamp 

or otherwise attach the drip racks 

only at the top of the drain board. 

Dipping 

Remove loose fibers and sawdust 

on each siding or decking piece 

before dipping. Brushing with a stiff 

bristle broom works well for this; 

additional loose fibers can be 

removed by tapping on the board or 

tapping it against something solid. 

Wearing long rubber gloves, dip 

each piece in the tank for 10 to 30 

seconds. With stains, it may be 

necessary to slosh each piece up and 

down a few times to keep the 

pigments suspended. Brushing with 

a stiff bristle broom improves the 

finish absorption. 

Figure 1Dip-tank (without end caps attached) shown with first piece of 

siding in rack. 
2 

Remove the piece and place it in the 

drip rack so that it leans toward the 

tank with its edge touching the base 

of the upper nail and its side leaning 

against the head of the lower nail. 

For siding, hold the piece with the 

thick edge up and the saw-textured 

(rough) side facing away from the 

tank; by placing it in the drip rack 

this way, any nail dents will be only 

on the back (smooth) side. (We 

strongly recommend installing 

siding on the structure with the sawtextured side out.) For very long and 

flexible pieces, you may find it 

necessary to use every other slot of 

the rack to keep the pieces from 

touching each other. 

Place the first board that was dipped 

in the lowest position (first position) 

on the rack. While the second board 

is soaking in the tank, move the first 

board to the second position. 

Remove the second board from the 

tank and place it in the first 

position. While the third board is 

soaking, shuttle the first and second 

boards up the rack to clear the first 

position. Continue the shuttling 

process. 

By the time the drip rack is full, the 

first piece that was dipped can be 

moved to another rack on a plasticcovered driveway, leaned against a 

sheathed wall, or installed (possible 

when using clear finishes). Do not 

stack the pieces until they are 

completely dry. 

Tips 

• A blue–black discoloration is 

caused by the reaction of wood 

extractives with iron. It is 

associated with the use of ferrous 

nails and iron traces from tools. 

Even for temporary dip tanks, it 

is best to use galvanized screws 

to construct the tank and drip 

rack. 

• If you are using waterborne 

finishes, reaction with iron is 

more likely to be a problem. In 

this case, be sure to use doubledipped galvanized or stainless 

steel fasteners for the drip rack. 

• Professionals may wish to make 

a more permanent reusable tank 

by taking greater care with 

construction. Thoroughly 

caulking the joints and finishing 

the surfaces of the tank may 

alleviate the need to carefully 

line the tank with plastic each 

time it is used. For this 

application, use only high-quality 

galvanized or stainless steel 

fasteners for the tank. 

• Cutting pieces to size before 

dipping alleviates the need to 

treat the cut ends in a separate 

procedure. 

Safety Precautions 

• Protect your hands with gloves, 

wear safety glasses, and take care 

to avoid fire. 

• Many solvent-borne finishes are 

quite flammable; rags and other 

material contaminated with the 

finish can spontaneously combust 

if not disposed of properly. Seal 

contaminated material in a metal 

container or soak in water. 

• If the finish contains a pesticide, 

contaminated material may be 

considered hazardous waste. 

Consult the manufacturer to 

determine proper disposal for 

waste materials. 

For more information, see Finishes 

for Exterior Wood, Forest Products 

Society, 2801 Marshall Ct., 

Madison, WI 53705–2295. (608) 

231–1361. $19.95 

http://www.fpl.fs.fed.us/ See FAQ 

Mark Knaebe and R. Sam Williams 

are researchers in Wood Surface 

Chemistry at the U.S. Department 

of Agriculture, Forest Service, 

Forest Products Laboratory, One 

Gifford Pinchot Dr., Madison, WI 

53705-2398 

March 2001