how to calculate amount of siding needed

Embarking on a siding project for your home is an exciting endeavor that can dramatically enhance curb appeal and protection. However, before you pick out colors and styles, a crucial first step is accurately calculating how much siding you'll need. Buying too little means delays and potentially mismatched batches, while buying too much is a costly waste. This guide, along with our handy calculator, will walk you through the process step-by-step.

Why Accurate Siding Calculation Matters

Precision in your material estimation isn't just about saving money; it's about efficiency and a smooth project flow. Here’s why it’s critical:

• Cost Savings: Avoid overspending on excess materials or incurring additional shipping costs for reorders.
• Time Efficiency: Prevent project delays caused by waiting for more supplies.
• Material Consistency: Siding, especially vinyl, can have slight color variations between different manufacturing batches. Buying enough at once ensures color uniformity.
• Waste Reduction: Minimizing excess material is better for your budget and the environment.

Step-by-Step Guide to Calculating Siding

Step 1: Measure Your Rectangular Walls

Most homes have a significant portion of rectangular walls. To measure these:

1. Measure Length: Go around your house and measure the length of each rectangular wall section. It's often easiest to measure the perimeter of the house, subtracting any non-siding sections (like brick facades). Sum these lengths to get your "Total Length of Rectangular Walls".
2. Measure Height: Measure the height of each rectangular wall from the foundation to the eaves. If heights vary, take an average, or calculate each wall separately and sum their areas. For simplicity in our calculator, we use an "Average Height of Rectangular Walls".
3. Calculate Area: Multiply the total length by the average height to get the total square footage for your rectangular walls.

Example: If your house has a perimeter of 80 feet and an average wall height of 8 feet, your rectangular wall area is 80 ft * 8 ft = 640 sq ft.

Step 2: Measure Your Gable Ends (Triangular Walls)

Gable ends are the triangular sections of walls found beneath a pitched roof. Calculating their area involves a simple geometric formula:

1. Count Gables: Determine how many gable ends your house has.
2. Measure Base Width: For each gable, measure the width of its base (the horizontal line where it meets the rectangular wall). If they are similar, you can use an "Average Base Width".
3. Measure Peak Height: Measure the vertical height from the base of the gable to its highest point (the peak). Again, an "Average Peak Height" can be used if they are similar.
4. Calculate Area: The area of a triangle is (0.5 * Base * Height). Multiply this by the number of gables.

Example: Two gables, each with a base of 25 feet and a peak height of 6 feet. Area = 2 * (0.5 * 25 ft * 6 ft) = 150 sq ft.

Step 3: Account for Openings (Windows & Doors)

You don't need siding for windows and doors, so these areas must be subtracted from your total wall area.

1. Measure Windows: Count all windows. Measure the width and height of each, or use "Average Window Width" and "Average Window Height" for similar-sized windows. Calculate the area of each (Width * Height) and sum them up.
2. Measure Doors: Count all doors (exterior doors only). Measure their width and height, or use "Average Door Width" and "Average Door Height". Calculate the area of each and sum them up.
3. Total Opening Area: Add the total window area and total door area together.

Example: 5 windows (3ft x 4ft each) = 5 * 12 sq ft = 60 sq ft. 2 doors (3ft x 7ft each) = 2 * 21 sq ft = 42 sq ft. Total opening area = 60 + 42 = 102 sq ft.

Step 4: Factor in Waste

It's impossible to install siding without some waste from cuts, mistakes, or damaged pieces. A "Waste Factor" is essential. Most professionals recommend adding 10-15% for waste. For complex homes with many angles or windows, you might consider slightly higher (e.g., 15-20%).

To apply the waste factor, subtract your total opening area from your total gross wall area (rectangular + gable). Then, multiply this "Net Siding Area" by (1 + Waste Percentage / 100).

Example: If your net siding area is 688 sq ft and you add 10% waste, you need 688 * 1.10 = 756.8 sq ft of siding.

Step 5: Convert to Siding Boxes or Units

Siding is typically sold in boxes or bundles, each covering a specific number of square feet (e.g., 200 sq ft per box for vinyl siding). Check the product specifications for the siding you plan to purchase to find its "Siding Coverage Per Box".

Divide your "Adjusted Area (with waste)" by the siding coverage per box. Always round up to the nearest whole number, as you can't buy a fraction of a box.

Example: If you need 756.8 sq ft of siding and each box covers 200 sq ft, you need 756.8 / 200 = 3.784 boxes. Rounded up, that's 4 boxes.

Tips for Greater Accuracy

• Measure Twice: Always double-check your measurements to avoid errors.
• Draw a Diagram: Sketch out each wall and opening, noting dimensions. This helps visualize and organize your measurements.
• Consider All Obstacles: Don't forget to account for areas like chimneys, large architectural features, or other non-siding elements that will reduce the needed area.
• Consult a Professional: If you're unsure, especially for complex homes, consider having a siding contractor provide a professional estimate. They often have specialized tools and experience.
• Buy a Little Extra: Even with a waste factor, having a small amount of extra siding (perhaps one extra box for large projects) can be beneficial for future repairs or unexpected issues.

Conclusion

Calculating the amount of siding needed is a straightforward process when broken down into manageable steps. By carefully measuring your walls, accounting for openings, adding a waste factor, and converting to the correct units, you can confidently purchase the right amount of material for your project. Use our interactive calculator above to streamline this process, and happy siding!