Restoration Guide: Wood Shingles on Exterior Walls
Editor's Note: This is article 9 of 18 in Chapter 2: Exterior Walls of the Old House Web's Restoration Guide. This guide was developed and edited for old homes from original materials in the U.S. Housing and Urban Development (HUD) Rehab Guide.
9. WOOD SHAKES AND SHINGLES
Section 1--The Basics
For more than three centuries, builders have clad (and roofed) the walls of homes and buildings in wood shingles and shakes. Shake or shingle siding is an attractive material used in historic and contemporary architecture. You can treat it with protective coatings or leave it exposed to the elements to weather naturally.
Chances are, if you undertake any preservation project on an old house, you'll run across this type of siding material and have to replace either individual shakes or whole wall sections if they've faced the sun for decades.
Most of the shingles and shakes manufactured today come from Canada and are made from:
- Western red cedar
- Eastern white cedar
- Alaskan yellow cedar
Southern yellow pine also is used to make shingles and shakes--thicker versions of shingles--once it's been pressure treated with wood preservatives. Redwood is also used to make shingles, but it's not very prevalent because of heavy discoloration when exposed to the elements. Western red cedar also tends to darken more than Eastern white or Alaskan yellow cedar.
1.1: Characteristics of Cedar Shakes and Shingles
Cedar shingles usually carry a 20-year warranty, or 30 years if they're pressure-treated with chromated copper arsenate (CCA). However, the safety of the wood treated with CCA is in question. The Environmental Protection Agency strictly regulates CCA because it's a highly toxic material. Most of the pressure-treated material sold today is treated with amine copper quat (ACQ)) or copper azone (CA).
The U.S. Department of Agriculture Forest Product Laboratory reports wood sold before 2004 was most likely treated with CCA.
Shakes and shingles are sold by classification depending on the grade of the material.
No.1 Blue Label:
- End grain
No.2 Red Label:
- Flat grain
- Limited sapwood
As with most woods, the higher the grade, the prettier the wood. No.1 grain is preferred for siding and roofing materials, but you can also use No.2 grade for siding because it doesn't take as much abuse from the weather. Lower-grade materials have more knots and imperfections and are sold at less-expensive prices than heartwood or clear wood.
Section 2--Replacing Single Shakes or Shingles
If your home renovation includes exterior walls with cedar shingles or shakes for siding, spend some time examining the cladding for defects such as curled, cracked or even missing siding.
To repair individual shingles:
- Free the damaged shingle using a hacksaw blade or reciprocating saw to cut the nail holding the siding
- Split the shingle with a hammer and chisel, and remove it
- Cut a new shingle to fit
2.1: Replacing Whole Wall Sections
In some cases, you don't need to remove existing cladding materials to apply a layer of cedar shingles as siding. If the existing siding is in good to fair shape, you can nail new shingles right over the top of the old material. Residing over old material significantly reduces the time and expense of ripping off the old siding materials.
If the existing siding is beveled, as is most wood lap siding, you need to apply 1x3" or 1x4" furring strips along the low points of the siding to make the wall surface flush. The furring strips, as well as plastic-mesh moisture management underlayment, such as Cedar Breather, help air circulate behind the shingles and reduce excessive moisture buildup.
2.2: Using Shingles over Stucco or Masonry
If you perform a home restoration on a stucco or masonry structure and want to use shingles for cladding, you must attach horizontal furring strips to the wall to provide a nailing surface. The furring also prevents moisture from accumulating behind the siding.
If the existing stucco or masonry is in poor condition, as in many old houses, it's best to remove the exterior cladding, building paper, and flashing materials and start from scratch.
2.3: Re-siding Around Corners and Windows
When running new siding, try to align butt lines with the tops and bottoms of windows for the best look. The exposure lines (overlap) should also be consistent. When running siding around corners, you can choose from three methods:
- butted against corner boards
- lacing edges together
- mitering edges with a saw
Keep this in mind when performing your old home restoration: although wood shingles may cost more than other siding materials, they provide unsurpassed elegance to certain types of residential and commercial buildings.