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1x3 Cumaru Shiplap Siding board profile diagram
Siding

1x3 Cumaru Shiplap Siding

This 1x3 Cumaru Shiplap siding board offers unmatched exterior cladding longevity, backed by Cumaru's 3,540 Janka hardness and a natural lifespan of up to 50+ years. The overlapping shiplap profile sheds water naturally and creates a classic, weather-resistant look for exterior cladding and accent walls. In stock and ships nationwide — order Cumaru siding online or call 1-844-674-4455 for expert guidance.

1 x 3(0.75"×2.5" actual)[19.0mm × 63.5mm]
Contractor Trusted
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Ships Nationwide
SKU: CUMA-1X3-SHIP-SB-L1

Configure Your Order

Select profile, grade, and length below to see live pricing

Premium Dimensional Stability and Weather Resistance

Shiplap

Select and Better is our standard grade

Length Guide

Available lengths: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22′

Estimated Shipping Weight
Weight per linear foot:0.91 lbs/LF
1' board:0.9 lbs

1x3 Cumaru Shiplap Siding — Complete Guide

Everything you need to know about shiplap cumaru siding

About 1x3 Cumaru Shiplap Siding

Cumaru lumber, known for its remarkable durability and aesthetic appeal, is an excellent choice for exterior siding and cladding applications. This particular product, featuring a shiplap profile, not only enhances the visual character of any structure but also provides superior dimensional stability and weather resistance essential for outdoor environments. The shiplap design creates distinct shadow lines that add depth and texture, allowing for versatility in installation orientation, either horizontally or vertically, catering to various architectural styles.

  • Superior dimensional stability ideal for fluctuating weather conditions.
  • Exceptional resistance to decay and insect damage.
  • Aesthetic shiplap profile enhances visual depth and shadow lines.
  • Versatile installation options for diverse architectural needs.

Key Benefits

Longevity

Cumaru's natural durability ensures a long lifespan in outdoor applications, reducing the need for frequent replacements.

Visual Appeal

The unique grain and color variations provide an attractive appearance that enhances the beauty of any building.

Low Maintenance

Its resistance to weathering and pests translates to lower maintenance requirements, saving time and costs over the years.

Technical Specifications

Janka Hardness

3330

Density

65 lbs/ft³

Durability Rating

Class 1 (very durable)

Dimensional Stability

High, with minimal movement in response to humidity changes.

Installation Guide

Difficulty:
Moderate

Key Tips:

  • Ensure proper spacing to accommodate expansion due to temperature changes.
  • Use premium stainless steel or coated fasteners to prevent corrosion.
  • Follow local building codes for ventilation and water management.

Recommended Tools:

Circular saw
Drill or driver
Measuring tape
Level

Maintenance & Care

Cleaning

Clean siding periodically with a mild soap solution and avoid harsh chemicals.

Finishing

Consider applying a UV protectant finish to maintain color and resistance to weathering.

Weathering

Expect a gradual natural aging process that may lead to a silver-grey patina over time.

Frequently Asked Questions

A 1x3 Cumaru board weighs approximately 0.91 lbs per linear foot. Cumaru has a density of about 68 lbs/ft³, making it one of the densest commercially available hardwoods. Always factor weight into your structural and shipping calculations.

Yes — Cumaru is rated Durability Class 1 (Very Durable) and is naturally resistant to rot, decay, insects, and fungal attack without chemical treatment. It is Class B fire-rated and performs exceptionally well in full exterior exposure including siding applications. While ground contact is possible, we recommend elevating Cumaru boards at least 6" above grade for maximum lifespan.

Cumaru outperforms composite in hardness (3,540 vs ~200 Janka), lifespan (up to 50+ years vs 25-30 years), and heat resistance. Unlike composites, Cumaru won't melt, warp in extreme heat, or fade significantly. While initial cost is similar ($8-15/LF installed), Cumaru costs less over its much longer lifetime. Composites do offer lower upfront maintenance.

Cumaru requires minimal maintenance. Without treatment, it naturally weathers to an elegant silver-gray patina over 6-12 months. To maintain the original warm brown color, apply a UV-inhibiting penetrating oil (like Ipe Oil or Penofin) once or twice annually. Cleaning involves periodic washing with a mild soap solution. No sanding, staining, or sealing is required for structural durability.

Cumaru is DIY-friendly with proper preparation. Key requirements: (1) Always pre-drill all screw holes — Cumaru is too hard for direct screwing. (2) Use only 305 or 316 stainless steel fasteners — standard hardware will corrode and stain. (3) Face-screw with stainless steel trim-head screws. (4) Allow boards to acclimate on-site for 5-7 days before installation. A compound miter saw with a carbide-tipped blade is recommended.

A nominal 1x3 Cumaru board has actual finished dimensions of 0.75" × 2.5" (19.0 x 63.5 mm). The "1x3" is the nominal (rough-cut) size — after kiln drying and precision surfacing, all hardwood lumber finishes slightly smaller. This is standard across the lumber industry, similar to how a nominal 2×4 softwood measures 1.5" × 3.5". Always use the actual dimensions (0.75" × 2.5") when calculating material quantities and coverage for your project.

We responsibly, legally, and ethically source all our Cumaru. We work only with suppliers who follow responsible forestry practices with full chain-of-custody transparency. Note: We are not FSC certified. Cumaru trees grow naturally in diverse tropical forests and regenerate well under managed harvest. The extremely long lifespan (up to 50+ years) means fewer replacements compared to softwood or composite alternatives, reducing long-term environmental impact.

Shipping & Delivery

Nationwide delivery: We ship to all 50 states via LTL freight, flatbed, or terminal pickup

Typical lead time: 5-10 business days for standard orders (custom milling may add 2-3 weeks)

Shipping estimate: Final freight cost calculated at checkout based on your location and order size

Rush service available: Contact us for expedited milling and shipping options

Alternative Siding Option

This same Cumaru 1 x 3 is also available in a different siding profile:

Rainscreen

Designed for rainscreen clip systems with ventilation gap

1 x 3 Cumaru Shiplap Siding — Complete Buyer's Guide

Cumaru, also known as Brazilian Teak, is a premium tropical hardwood sourced from Amazon Basin, northern South America (Brazil, Venezuela, Guyana). With a Janka hardness rating of 3,330 lbf and a density of 65 lbs/ft³, Cumaru is classified as Class 1 - Very Durable — one of the most durable commercial lumber species available. The heartwood exhibits light to medium brown with reddish tones with interlocked grain, medium to coarse texture, creating a striking natural appearance that improves with age.

As exterior cladding, Cumaru siding provides a weather-tight barrier with exceptional impact resistance. The dense grain resists dents, hail damage, and woodpecker damage far better than cedar, pine, or fiber cement alternatives. Properly installed Cumaru siding delivers a service life of 50+ years with minimal maintenance — an optional annual oil treatment preserves the original color, or you can let the wood weather to a distinguished silver-gray patina. Cumaru carries a Class A - Low flame spread, making it suitable for wildfire-prone regions where code-compliant materials are required.

The 1 x 3 shiplap profile creates an overlapping joint with a distinctive shadow line between boards. Popular for siding, accent walls, and architectural cladding applications. All Cumaru lumber is available in Select and Better grade with lengths ranging from 4′ to 20′. For detailed step-by-step instructions, consult our Cumaru installation guide. Long-term care recommendations are covered in our Cumaru maintenance guide.

Janka Hardness

3,330 lbf

Service Life

50+ years

Durability

Very Durable

Fire Rating

Class A

1 x 3 Cumaru Siding — Frequently Asked Questions

Cumaru siding has an expected service life of 50+ years when properly installed and maintained. This is 3-5x longer than pressure-treated pine and 2-3x longer than cedar. Cumaru achieves this exceptional longevity through its natural density (Janka hardness: 3,330 lbf) and Class 1 durability rating, which provide built-in resistance to rot, decay, insects, and fungal growth — all without chemical preservatives.

Use 305 or 316 stainless steel screws for all Cumaru installations — never use galvanized or coated deck screws, which will corrode and stain the wood. Pre-drill every hole using a countersink bit sized for your screw. For 1 x 3 boards, place screws approximately 1" from each edge and 3/4" from board ends. A combination drill/driver with a clutch setting prevents over-driving into this extremely hard wood.

Cumaru siding pricing varies by size, profile, grade, and board length. 1 x 3 Shiplap boards in Select and Better grade typically range from $4-$12 per linear foot before shipping. While the upfront cost is higher than pressure-treated lumber, Cumaru's 50+ years service life makes the lifetime cost per year significantly lower. Use our online configurator above to see exact pricing for your selected options, or request a custom quote for large orders.

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