Drill Through Composite Decking

Drilling through composite decking requires specific techniques and tools to achieve professional results without damaging your investment. Whether you’re installing railings, adding fixtures, or making repairs, knowing the correct approach to drilling composite material is essential. This article will walk you through everything you need to know about properly drilling through composite decking to ensure long-lasting, attractive results.

Understanding Composite Decking Construction

Before drilling into your composite decking, it’s important to understand what you’re working with. Composite decking comes in two main types:

Solid composite boards – Made of uniform material throughout, these can typically be drilled through with proper techniques
Hollow composite boards – Feature hollow channels that reduce weight and cost but require special consideration when drilling

The composition typically includes a blend of wood fibers, plastic polymers, and binding agents. This combination creates a durable material that resists rot and insects but requires different drilling approaches than traditional wood.

Essential Tools and Materials

Tool/Material	Purpose	Recommendation
Power Drill	Primary drilling tool	Variable speed, 18V or higher
Drill Bits	Creating holes	High-quality brad point or specialized composite bits
Countersink Bit	Creating recessed screw heads	Specialized composite countersink
Tape Measure	Accurate measurements	16ft minimum with clear markings
Pencil/Marker	Marking drill locations	Carpenter’s pencil or erasable marker
Composite Decking Screws	Specialized fasteners	Stainless steel, composite-specific screws
Safety Glasses	Eye protection	ANSI-rated safety glasses
Dust Mask	Respiratory protection	N95 or equivalent

Step-by-Step Process for Drilling Through Composite Decking

1. Determine Board Type (2-3 minutes)

First, identify whether you’re working with solid or hollow composite decking. Tap on the surface and listen for a solid or hollow sound. Alternatively, check the board edges – hollow boards will have visible channels.

Important: It is not advised to screw or drill directly through hollow composite decking boards. You should only drill through solid composite decking boards and always pre-drill before inserting screws.

2. Mark Your Drilling Locations (1-2 minutes per mark)

Use a pencil or erasable marker to clearly indicate where you need to drill. For precise placement, consider using a small template if drilling multiple holes in a pattern.

When installing railings or other fixtures, double-check measurements before marking to ensure proper alignment and spacing.

3. Select the Appropriate Drill Bit (1 minute)

Choose a drill bit based on your specific needs:

For pre-drilling screw holes: Select a bit slightly smaller than your screw diameter (typically 1/16″ smaller)
For creating pass-through holes: Use a brad point bit for cleaner entry and exit points
For larger holes (such as for lighting or plumbing): Use a hole saw designed for composite materials

4. Set Up Your Drill Properly (2 minutes)

Adjust your drill to the appropriate settings:

Set to medium speed – high speeds can create excess friction and melt the composite material
Use moderate pressure – too much force can damage the decking
For cordless drills, ensure the battery is fully charged for consistent power

5. Pre-Drilling Process (1-2 minutes per hole)

Pre-drilling is essential for composite decking to prevent splitting, mushrooming, and other damage:

Position your drill perpendicular to the decking surface
Start drilling slowly to create an initial depression
Gradually increase to medium speed
Apply steady, moderate pressure
Periodically pull the bit out to clear debris
Continue until you’ve reached the desired depth

For screw holes, drill to a depth slightly greater than the screw length to accommodate any material displacement.

6. Countersinking for Screw Heads (1 minute per hole)

If you’re installing screws that will be visible, countersinking creates a cleaner finished appearance:

After pre-drilling, switch to a countersink bit
Drill just deep enough to create a recess for the screw head
Avoid drilling too deep, which can weaken the material

Some composite-specific screws come with built-in countersinking features, which can simplify this process.

7. Installing Screws (1 minute per screw)

After pre-drilling, insert screws carefully:

Select composite-specific screws (typically stainless steel with special threading)
Set your drill/driver to medium torque
Drive the screw in slowly and steadily
Stop when the screw head is flush with the countersink or surface
Avoid over-tightening, which can strip the hole or damage the board

8. Creating Larger Holes (3-5 minutes per hole)

For larger openings such as for lighting or plumbing:

Start with a pilot hole using a small drill bit
Switch to a hole saw of the appropriate diameter
Drill from the top side at medium speed
Apply steady pressure without forcing
If possible, place a scrap board underneath to support the exit point

Special Considerations for Hollow Composite Decking

While it’s generally not recommended to drill directly through hollow composite decking, there are situations where it may be necessary. In these cases:

Locate the solid sections between hollow channels when possible
Use a backer plate or blocking beneath the decking for added support
Consider specialized hollow-board fasteners designed for this purpose
Consult the manufacturer’s guidelines for your specific decking brand

For hollow boards, many manufacturers recommend using their proprietary hidden fastening systems rather than drilling through the boards.

Hidden Fastening Systems: An Alternative to Drilling

Many composite decking manufacturers recommend hidden fastening systems as an alternative to drilling through the boards:

Clips that fit into grooved board edges
Track systems that attach to the joists
Edge fasteners that secure the board from the sides

These systems provide a cleaner appearance without visible screw heads and often preserve your warranty coverage. A 6mm clip typically has a gap wide enough to position a drill for easy removal of one or two boards if needed for repairs.

Common Mistakes to Avoid

Drilling Without Pre-Drilling

Drilling directly into composite decking without pre-drilling often results in “mushrooming” – where the material bulges around the screw head. This creates an unattractive appearance and can compromise the integrity of the installation. Always pre-drill to prevent this issue.

Using Incorrect Screws

Standard wood or deck screws are not designed for composite materials. They can cause splitting, discoloration, or premature failure. Always use screws specifically designed for composite decking.

Drilling at High Speeds

High-speed drilling generates excessive heat that can melt the plastic components in composite decking. This melting can lead to weakened holes and an unattractive finish. Maintain medium drill speeds throughout the process.

Over-Tightening Screws

Composite material doesn’t compress like wood. Over-tightening screws can strip the hole, crack the material, or create depressions in the surface. Drive screws until they’re just flush with the surface.

Troubleshooting Common Issues

Problem	Cause	Solution
Material “mushrooming” around screw	No pre-drilling or inadequate pre-drilling	Always pre-drill with the correct bit size; consider countersinking
Cracking or splitting	Drilling too close to board edge or using incorrect technique	Maintain at least 1″ distance from edges; use sharp bits and proper speed
Screws not holding securely	Hole too large or improper screw type	Ensure pre-drill size is smaller than screw; use composite-specific screws
Melted material in hole	Excessive drill speed creating heat	Reduce drill speed; clear debris frequently during drilling
Discoloration around screw	Chemical reaction with incorrect screw type	Use only stainless steel or composite-approved screws

Manufacturer Guidelines and Warranty Considerations

Before drilling through your composite decking, be aware that doing so may affect your warranty coverage:

Many manufacturers specify that drilling through the face of boards may void or limit warranty protection
Some brands allow face screwing in specific circumstances but require pre-drilling
Most manufacturers recommend their proprietary hidden fastening systems

Always check your specific decking brand’s installation guidelines and warranty terms before proceeding with any drilling. When in doubt, contact the manufacturer directly for clarification.

Alternative Methods for Cutting Larger Holes

For creating larger openings in composite decking, such as for lighting fixtures or plumbing access:

Jigsaw with reverse-cut blade – As recommended by professionals, jigsaws with reverse-cut blades (that cut on the downstroke) provide cleaner cuts in composite material
Hole saws – Available in various diameters, these attachments work well for circular openings
Forstner bits – For precise, flat-bottomed holes of larger diameter

When using a jigsaw, mark your cutting line clearly and secure the board to prevent vibration. Use a new blade designed for cutting plastic or composite materials for the best results.

Final Tips for Professional Results

Always work on a warm, dry day – cold composite material is more brittle and prone to cracking
Keep drill bits clean and sharp for cleaner holes
Consider making a test hole in a scrap piece or inconspicuous area first
Have touch-up paint or matching filler on hand to address any minor damage
For critical structural connections, consult a professional deck builder

By following these guidelines, you can successfully drill through composite decking when necessary while maintaining the appearance and integrity of your deck. Remember that proper preparation and technique are key to achieving professional results that will last for years to come.