Zinc-plated mushroom head roofing bolts with square nuts, available in a full range of sizes from M5 x 12mm up to M10 x 240mm. The square neck beds into timber and stops the bolt spinning when you tighten the nut.
Size
QTY
Price
QTY
M10 x 240mm
25
£24.85£29.82
m5 x 12mm
250
£4.46£5.35
M6 x 16mm
200
£4.89£5.87
M6 x 25mm
100
£4.75£5.70
M8 x 120mm
50
£8.93£10.72
M8 x 160mm
50
£13.50£16.20
ZP mushroom head roofing bolts are one of those fixings that turn up on almost every site sooner or later. The wide, low-profile dome head spreads load across a larger surface area than a standard hex bolt, which is exactly what you want when fixing sheeting, cladding, or purlins where over-tightening could pull through the material. The square neck just below the head locks into timber or pre-punched square holes, so the bolt stays put while you run the nut up from the other side. No spinning, no drama.
These are zinc-plated, giving a decent level of corrosion resistance for most covered or semi-exposed applications. Light gauge steel roofing, corrugated sheeting, timber frame assemblies, agricultural buildings — they all call for this type of fixing regularly. The mushroom profile also sits flush and unobtrusive once installed, which matters on visible elevations.
Where ZP Mushroom Head Roofing Bolts Get Used
On site, these bolts earn their keep fixing metal roofing sheets and cladding panels to structural members. They are also common in fencing assemblies, gate hardware, and any lightweight structural connection where a flat-bearing head is preferable to a countersunk or hex arrangement. The square neck function is particularly useful in softwood, where a round-neck bolt would simply rotate as you apply torque.
Size Range and Selection
We stock sizes from M5 x 12mm right up to M10 x 240mm. The longer lengths — M8 x 160mm, M8 x 240mm and M10 x 240mm — are there for when you are passing through multiple layers: insulation board, sheeting, and a purlin in one go. Short sizes like M5 x 12mm and M6 x 16mm suit lighter panel work where reach is not the issue. Picking the right length matters; too short and the nut barely engages the thread, too long and you are just left with exposed shank flapping in the breeze.
Available in trade box quantities with pricing that makes bulk buying straightforward. If you need a size or quantity not shown, get in touch — we hold a wider range than what is listed here and can sort pricing on volume orders.
Pro Tip: When fixing corrugated metal sheeting, always bolt through the crown of the corrugation, not the valley — water sits in the valley and any gap around the shank becomes a rust and leak point within a season.
Mushroom head roofing bolts are used across agricultural, industrial and commercial construction for fixing metal roofing sheets and cladding panels to steel purlins or timber rafters. They are a standard fixing on portal frame barns, storage units, and light industrial buildings. Beyond roofing, they appear in fencing, gate hanging, and general structural timber connections where a wide-bearing head and anti-rotation neck are needed. Any trade fixing sheeting or cladding regularly will get through boxes of these.
Best For
Metal roofing sheet fixings
Cladding panel installation
Timber frame connections
Agricultural and industrial buildings
Fencing and gate assemblies
Light structural fixings
Works With
Corrugated metal roofing sheets
Steel purlins and rails
Softwood and hardwood timber
Pre-punched square hole fixings
Standard square nuts (supplied)
Key Specifications
Finish: Zinc plated (ZP)
Head style: Mushroom (low-profile dome)
Neck: Square anti-rotation
Sizes: M5 x 12mm to M10 x 240mm
Supplied with matching square nuts
Available in boxes of 25, 50, 100, 200, 250
Not suitable for: Not suitable for fully exposed coastal or marine environments where hot-dip galvanised or stainless fixings should be used instead. These are low load bearing fixings and are not appropriate for structural bolted connections carrying significant shear or tensile loads.
Select the correct bolt length for your stack-up: the thread should protrude enough past the nut to engage fully, typically at least two thread pitches beyond the face of the nut. Drill or use pre-punched holes sized to match the bolt shank. The square neck must locate into a square hole or press into the timber grain to prevent rotation.
Fit the bolt from the top or face side, push the square neck home, then fit the square nut from the reverse side and tighten with a spanner or socket. Do not over-torque on thin sheeting — snug is enough. The mushroom head should sit flat against the surface without distorting the sheet.
Select the correct size: match bolt diameter to the pre-drilled or pre-punched hole specification for your sheeting or component
Check your length allows the nut to fully engage the thread on the reverse side with at least two threads to spare
Drill or confirm hole size — the square neck needs to locate cleanly, not rattle around
Insert the bolt from the face side, seating the square neck into the hole to prevent rotation
Fit the square nut to the protruding thread on the reverse side by hand first
Tighten with a spanner or socket to a snug fit — avoid over-tightening on lightweight sheeting materials
What is the square neck for on a roofing bolt?
The square section just below the head locks into a square hole in metal sheeting or bites into the grain of timber, stopping the bolt from rotating when you tighten the nut from the other side. Without it you would need two people or a second tool to hold the bolt head — the square neck means one person can do the job.
Are these suitable for external use on roofing in all weather conditions?
The zinc plating gives reasonable corrosion resistance for most covered, semi-exposed, or inland outdoor applications. For fully exposed or coastal environments, or anywhere with prolonged standing water contact, hot-dip galvanised or A2 stainless roofing bolts are a better choice for long-term performance.
These bolts are manufactured from steel with a zinc plate finish, providing a standard level of corrosion protection suitable for general construction use in non-aggressive environments. The mushroom head profile gives a wide bearing surface and a low visual profile. Thread form is standard metric coarse, supplied with matching square nuts. Available across a range of metric sizes from M5 through to M10 in various lengths.
Material
Steel
Finish
Zinc Plated (ZP)
Head Style
Mushroom (low-profile dome)
Neck Type
Square anti-rotation
Thread Form
Metric coarse
Size Range
M5 x 12mm to M10 x 240mm
Supplied With
Square nuts
Available Sizes
M5 x 12mm, M6 x 16mm, M6 x 25mm, M8 x 100mm, M8 x 120mm, M8 x 160mm, M10 x 240mm
Box Quantities
25, 50, 100, 200, 250
Weight
N/A
Size
M10 x 240mm, m5 x 12mm, M6 x 16mm, M6 x 25mm, M8 x 100mm, M8 x 120mm, M8 x 160mm
Box Quantity
100, 200, 25, 250, 50
Product Type
Mushroom Head Roofing Bolts & Square Nuts
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