Lap Siding
Uses
Lap sidings are normally supplied in a variety of patterns either green (unseasoned) or dry in clear or knotty grades and with a smooth or saw textured face.
Channel Siding
Channel siding is a popular type of lap siding and is used whenever a rustic appearance is desired. A versatile siding, it can be installed vertically, horizontally or diagonally. In channel siding the profile of each board partially overlaps that of the board next to it creating a channel that gives shadow line effects, provides excellent weather protection and allows for dimensional movement.
Grades
Channel siding is normally supplied in unseasoned knotty grades. The face side is saw textured. Commonly available sizes are 1"x6", 1"x8", and 1"x10". Clear grades are manufactured to order.
Channel Siding Diagrams
Grades
Clear Grades | Grade | Description |
 | Clear Heart The highest grade. Includes only pieces with heartwood on the exposed face. Many pieces completely clear, others have minor imperfections that do not detract from their fine appearance. Grading Rule Paragraph |
 | A Clear Permits somewhat more imperfections than Clear Heart but the grade is still restricted to pieces with excellent appearance. Common specifications are A and Better and A and Better with a percentage of B grade allowed. Grading Rule Paragraph |
 | B Clear Permits slightly larger and more numerous characteristics than A grade and occasional pieces may require trimming to yield high grade pieces in shorter lengths. Most often supplied as a percentage with A grade. Grading Rule Paragraph |
Knotty Grades | Grade | Description |
 | Select Knotty Available kiln dried or unseasoned. Knots are sound and tight. Grading Rule Paragraph |
 | Quality Knotty In this grade, natural growth characteristics are not limited as stringently as in Select Knotty. Cross cutting may be required on some pieces to yield tight knotted siding. Grading Rule Paragraph |
 | Proprietary Grades Designed to meet appearance requirements for cedar sidings and trim. Ask your WRCLA distributor for details. Manufacturers may market their own proprietary grades. Grading Rule Paragraph |
 | Standard and Better Suitable for exterior construction. Occasional pieces may require trimming to yield suitable quality for the intended end use. Grading Rule Paragraph |
NLGA - National Lumber Grades Authority
WCLIB - West Coast Lumber Inspection Bureau
Sizes
Coverage Table for Green (Unseasoned) Siding
| Nominal Width (inches) | Dressed Width (inches) | Exposed Face Width (inches) | Linear Feet Factor | Board Feet Factor |
| 6 | 5-1/2 | 4-3/4 | 2.53 | 1.27 |
| 8 | 7-3/8 | 6-5/8 | 1.81 | 1.21 |
| 10 | 9-3/8 | 8-5/8 | 1.39 | 1.16 |
Specifications
The following information is required when specifying lap siding products:
| Specification Information Required | Sample Specification |
Species:
Western Red Cedar | WRCLA Western
Red Cedar |
Product Pattern and Intended Use:
Siding is used as an exterior cladding to provide both weather protection and architectural style. The designer may choose from a variety of lap siding patterns specified by name or pattern number. | Lap Siding Pattern WP11 |
Size:
Specify the nominal size of the product. | 1 x 6" |
Grade:
The grade of the product governs its overall quality. Refer to WRCLA specification literature or grading agency rule books for available grades. | Select Knotty |
Grading Agency Paragraph:
To ensure that the product meets a written standard, an agency grade paragraph should be referenced. | NLGA para. 204a |
Moisture Content:
Specify whether the product is to be green (unseasoned) or kiln-dried. | Green |
Surface to be exposed:
Specify the application orientation to assist the supplier in shipping the right product for the job. | Sawn face |
Quantity:
Express in board feet the quantity required. See WRCLA table for factor to convert square feet of wall area to board feet. | 5500 board feet |
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