If your historic house or building has clapboard wood siding, you may occasionally find cracks or splits in the wood. Any pieces of clapboard siding that have large cracks or splits will need to be replaced.

Historic clapboard wood siding can become very brittle over time, so removing a damaged piece is a bit like a surgical process. If you are not careful, you can create additional problems with the wood above and below the siding piece you're trying to replace.

Evaluate the Damage

Make a point each spring to closely inspect your exterior wood siding for large splits, cracks or rot. Horizontally laid clapboard siding will occasionally split or crack along the grain lines. When you find a damaged piece of siding, you must decide whether to repair or replace it:

• If you find damage with less than a 1/16-inch gap, you can use a filler to repair these small splits.
• If you find a split or crack wider than 1/16 inch, wood rot or excessive cupping, you should replace the piece of siding by following the instructions below.

Gather Your Tools and Supplies

To replace damaged clapboard wood siding, you’ll need the following tools and supplies:

• Flat pry bar with v-notch in the flat and hooked ends
• Duct tape to wrap on the heel of the pry bar
• Staple gun with ¼-inch staples
• Bastard file (metal file)
• End cutters for prying out nails
• Hammer and nail set
• Utility knife for scoring
• Small spray bottle with water
• Tape measure
• Power or hand miter box
• Pencil
• #6 exterior grade, hot-dipped galvanized, finish casing nails
• Glazing compound to fill nail holes
• 15-pound building felt (tar paper)
• Siding to match your original

Prepare Your Tools and Supplies

It is always a good idea to keep a small amount of your clapboard wood siding type on hand. Architectural salvage businesses can usually provide old siding to match yours in width, thickness and profile as well. If you do not have any salvaged pieces of clapboard siding, you will have to purchase new clapboard siding. Clapboard wood siding is readily available through your local lumber yard or online.

If your house is primed and painted, you can purchase pre-primed siding or get some primer to coat your new siding pieces before painting them. Apply the primer to all sides of the clapboards (if they are not pre-primed). If your house has a solid-body stain, be careful not to purchase pre-primed siding.

You can create your own wood siding and wood shingle removal tool with a standard flat pry bar. Flat pry bars have a straight end and a hooked end. Both ends have a small v-notch in the center. Use a bastard metal file to file both sides of the v-notch until the edges are sharp. This sharpened v-notch will easily cut through nails.

Wrap duct tape around the heel of the pry bar. The heel is the spot on the flat or hooked end where the prying pressure is applied. The duct tape will create a padded area that will cushion the good wood and prevent it from being dented or marred.

Remove and Replace a Piece of Clapboard

Follow these steps to remove and replace a piece of damaged clapboard siding.

Step 1

Enlarge

Step 1

Source: Bob Yapp

Locate the two butt ends of the damaged piece of siding. The ends could be in the middle of a course or at a vertical casing. Use a spray bottle to lightly mist the face of the clapboard, the two butt ends and the top and bottom horizontal joints. The mist of water helps to control dust from the old paint on the board.

Step 2

Enlarge

Step 2

Source: Bob Yapp

Use a utility knife to score through the old paint on all four joints. Use the utility knife to horizontally score down the middle of the damaged clapboard from butt end to butt end and with the grain. Keep rescoring until the utility knife penetrates completely through the clapboard and splits it in half along its length. Splitting the clapboard should be relatively easy to do because the middle of the clapboard is only 3/16- to 1/4-inch thick.

Step 3

Enlarge

Step 3

Source: Bob Yapp

Pull the top half of the split clapboard out from under the board above it. This leaves only the nailed bottom half of the split clapboard to remove.

Tip: If the top half of the split clapboard does not come out easily, rescore the paint line or use a pair of pliers to gently pull it out.

Step 4

Enlarge

Step 4

Source: Bob Yapp

Insert the hook end of the pry bar under the remaining half of the clapboard from the top and pry off the piece of clapboard. If the nails holding this half of the board are cut nails (also known as square nails), the piece should come out easily with the nails in tow. If the nails are the more modern wire nails, you might have more trouble removing them.

Tip: If the nails will not come out easily, insert the flat end of the pry bar into the joint of the piece of siding from above. Use the sharpened v-notch in the pry bar to go over each nail from under the piece of siding. Use a hammer to give the pry bar a couple of swift blows. This force should cut through the nails, freeing the bottom piece of clapboard. If any nails or pieces of nail remain, gently pry them out of the wood with the end cutters.

Step 5

Enlarge

Step 5

Source: Bob Yapp

Check the building paper under the area where you removed the siding. This paper will most often be building felt (tar paper) or occasionally red rosin paper. If the building paper is in good condition, move on to the next step. If the building paper is torn or damaged, you'll need to replace it. Cut a piece of 15-pound building felt (tar paper) to fit into the area where you removed the siding. Staple the building felt in place.

Step 6

Enlarge

Step 6

Source: Bob Yapp

Cut a piece of new or salvaged clapboard to the length that will fit snuggly into the area of removed siding. Use a hand miter box or a power miter box to cut the ends squarely.

Step 7

Enlarge

Step 7

Source: Bob Yapp

Slip the top edge of the clapboard under the bottom butt edge of the piece above. Note how much your replacement piece overlaps the piece below it so you can determine where to place the nail. You want to make certain you do not nail through the top edge of the lower piece. For example, if the new piece laps 1/2 inch over the piece below it, then you should nail it about 5/8 inch from the bottom butt edge.

Step 8

Enlarge

Step 8

Source: Bob Yapp

Use #6 exterior-grade, hot-dipped galvanized, finish casing nails to nail the siding in place every 8 to 12 inches. Set these nails 1/8 inch below the surface. Fill the nail holes with glazing compound. Sometimes the nails holding the piece above the replaced piece will loosen a bit. If this happens, re-nail the loosened piece to the replaced piece. Apply two coats of exterior paint or solid-body stain to match the siding around the patch.

The information presented here is not intended to provide comprehensive technical advice or instructions on solving historic preservation issues. Any information contained or referenced is meant to provide a basic understanding of historic preservation practices. Read full disclaimer.