Coach screws, also known as lag screws, are heavy-duty hexagonal head fasteners designed for applications requiring exceptional holding power in timber and masonry. Distinguished by their coarse threading and robust construction, these essential fixings excel where standard wood screws simply cannot provide adequate strength. The hexagonal head design allows installation using a spanner or socket, delivering superior torque transfer for secure, load-bearing connections in structural applications.

MyToolShed.co.uk stocks quality coach screws manufactured from high-grade materials including A2 304 stainless steel, offering excellent corrosion resistance for both interior and exterior projects. Available in various lengths and diameters, these versatile fasteners feature a partially threaded shaft with an unthreaded shank section that allows materials to be drawn tightly together. Whether you're working with softwood, hardwood, or timber-to-masonry connections, coach screws provide the dependable strength that demanding construction and carpentry projects require.

Applications

Coach screws are indispensable fixings for trades and projects requiring robust structural connections:

Carpenters and Joiners – heavy-duty timber framework and structural connections
Builders and Contractors – securing timber joists to masonry, concrete and steel substrates
Decking Specialists – fixing joists to supports and installing load-bearing decking components
Roofers – securing rafters, purlins and structural roofing timbers
Fencing Contractors – assembling robust fence posts and gate structures
Landscape Gardeners – constructing pergolas, raised beds and outdoor timber features
Shopfitters – installing heavy shelving, display units and commercial fixtures
DIY Enthusiasts – home improvement projects requiring strong, reliable fixings

Choosing The Right Coach Screws

Material and Coating: For exterior applications or damp environments, specify stainless steel coach screws such as A2 304 grade to prevent corrosion. Zinc-plated options are suitable for dry, interior conditions and offer a more economical choice.

Size Selection: Choose a length that penetrates at least 50mm into the substrate material for adequate holding power. The diameter should be proportionate to the load – heavier applications require larger gauge screws. As a general rule, the threaded portion should extend at least halfway into the receiving material.

Installation Requirements: Always drill pilot holes approximately 60-70% of the screw's core diameter to prevent timber splitting and ensure proper installation. Verify you have the correct spanner or socket size before purchasing, and consider stainless steel washers to distribute load across the timber surface.

Quantity and Spacing: Calculate requirements based on typical spacing of 300-600mm centres, depending on load calculations and building regulations for your specific application.

Safety Information

Always wear safety glasses when drilling pilot holes or driving coach screws to protect against wood chips and metal fragments. Never attempt installation without pre-drilling appropriate pilot holes, as this prevents timber splitting and reduces the risk of fastener failure. Use properly sized tools that fit the hexagon head precisely – ill-fitting spanners can slip and cause injury. For structural applications, ensure compliance with relevant building regulations and consult a structural engineer if uncertain about load-bearing specifications.

Frequently Asked Questions

Do I need to drill a pilot hole for coach screws?
Yes, always drill a pilot hole before installing coach screws. The pilot hole should be approximately 60-70% of the screw's core diameter. This prevents timber splitting, makes installation easier and maintains optimal holding power.

Can I use coach screws in masonry or brick?
Yes, but you must first drill a hole and insert a suitable wall plug. The plug diameter should match the coach screw's outer thread diameter. For heavy-duty masonry applications, MyToolShed.co.uk recommends consulting load tables or considering resin anchors for superior holding power.

What's the difference between standard steel and stainless steel coach screws?
Stainless steel coach screws, such as A2 304 grade, offer excellent corrosion resistance for exterior and damp environments. Standard zinc-plated steel options are suitable for dry, interior applications and provide a more economical solution where rust prevention is less critical.