How to Install Coach Bolts and Screws for Maximum Holding Power

When working on timber structures, decking, fencing, or heavy-duty joinery, the strength and security of your fixings is essential. Coach bolts and coach screws are designed to provide strong, reliable connections in wood and other materials but to get the best results, proper installation is key. 

At Speedy Fixings, we stock a wide range of high-quality coach bolts and coach screws, ideal for both professional and DIY use. In this guide, we explain how to install them correctly to ensure maximum holding power and durability. 

What Are Coach Bolts and Coach Screws? 

It’s important to know the difference between the two: 

  • Coach Bolts (also known as carriage bolts or cup square hex bolts) have a domed head and a square neck beneath the head. They’re designed for through-bolting applications and are tightened using a nut on the threaded end. 
  • Coach Screws are large, heavy-duty screws with hexagonal heads and course screw threads. They are screwed directly into timber. 

Both are commonly used in structural timberwork, garden construction, sleepers, fencing, and securing posts. 

 

Tools and Materials You’ll Need 

  • Appropriate drill bits (pilot hole for screws + clearance hole for bolts) 
  • Washers (recommended for spreading load) 
  • Tape measure and pencil for marking 

 

How to Install Coach Bolts 

  1. Drill a clearance hole through both pieces of timber you’re connecting, this hole should match the diameter of the bolt shaft. 
  1. Tap the bolt into place so that the square neck bites into the timber, stopping it from rotating when the nut is tightened. 
  1. Slide a washer onto the protruding thread, then hand-tighten the nut onto the end. 
  1. Use a spanner or socket wrench to tighten the nut securely. Avoid over-tightening, which can crush the timber. 
  1. Double-check alignment and that the head sits flush for a neat finish. 

Tip: Use stainless steel or galvanised coach bolts for outdoor or treated timber to avoid rust and corrosion. 

How to Install Coach Screws 

  1. Mark and drill a pilot hole smaller than the screw diameter to prevent splitting and make driving easier. 
  1. If a flush finish is required, counterbore the hole large enough to fit the washer. 
  1. Slide a washer under the hexagon head. 
  1. Position the screw and use a socket wrench or impact driver with the correct socket to drive it into the timber. 
  1. Tighten until secure. 
  1. Tip: Pre-drilling is especially important for hardwood or close-to-edge applications to avoid cracking. 

Shop Coach Bolts and Screws at Speedy Fixings 

Installing coach bolts and screws correctly will ensure your structures are strong, safe, and built to last. Whether you’re building a garden structure or working on a major timber frame, Speedy Fixings has the right fasteners for the job. 

Browse our full range of coach bolts and screws and order online for fast UK delivery and competitive pricing.