5 Common Unistrut Installation Mistakes (And How to Fix Them)

Unistrut installation mistakes are more common than you might think—especially across UK construction, M&E, and HVAC projects. These support systems are strong, adaptable, and widely used, but even small installation errors can lead to expensive rework or system failure. This guide outlines the 5 most common mistakes and shares expert channel fixing tips to help avoid them.

Unistrut Installation Mistake #1: Using the Wrong Size or Type of Channel Nut

Channel nuts might seem minor, but they are fundamental to the integrity of your support system. Choosing the wrong thread size, material, or nut type can lead to loose fixings, system instability, and even failure under load.

✅ UK Example: A Wolverhampton warehouse installation used non-spring nuts in vertical cable supports. The result? Misalignment during install and time-consuming adjustments.

🔧 Use spring channel nuts for vertical or overhead installations.
🧩 Match M8, M10, or M12 threads precisely to bolts.
✅ Always test-fit nuts in the strut before final tightening.

Mistake #2: Overloading the Strut Channel

Every strut profile has a rated load capacity based on its size, wall thickness, and span. Ignoring these values can result in deflection, collapse, or ongoing safety issues—especially in dynamic environments like mechanical or rooftop systems.

📉 Load Capacity Example: HVAC ducting in a Midlands shopping centre sagged significantly after two months. It was originally supported by 1.5mm slotted channel instead of the recommended 2.5mm profile.

📊 Chart: Typical Load Capacity of Strut Channels (1m Span, Uniform Load)

Unistrut installation mistakes - Load capacity of strut channels

📐 Always refer to manufacturer load tables (e.g. MFMA or equivalent UK specs).
💡 Spread load using twin channel runs or intermediate brackets when necessary.
🛡️ Upgrade to 2.5mm HDG channel for high-load applications.

Mistake #3: Skipping Back Plates on Wall-Mounted Brackets

Wall fixings are a potential failure point—especially when heavy-duty loads are involved. Skipping back plates is a common oversight that can weaken the entire system over time.

🏗️ UK Site Example: A Manchester university server room had cable trays pull loose from blockwork walls. Retrospective installation of back plates and heavier anchors resolved the issue.

🔩 Always use back plates for wall brackets.
🧱 Choose fixings suitable for concrete, brick, or thermalite blocks as appropriate.
🔒 Anchor spacing should be ≤600mm for continuous support lines.

Mistake #4: Misalignment and Poor Levelling

Precision is everything. Even minor misalignments can result in stress on joints, misfitting accessories, or unsightly sagging—particularly in visible mechanical or electrical runs.

📏 On-site Error: A contractor in Birmingham fitted a 10m rooftop rail without a level. Result: two sections were out by 12mm, preventing clamping and requiring full refit.

🔦 Use a laser level or spirit level—especially for runs >2m.
🎯 Mark drill points in advance using chalk or pens (not freehand).
🔄 Check alignment at every bracket, not just the start and end.

Mistake #5: Choosing the Wrong Material or Finish

Material finish matters. Using bright zinc-plated (BZP) components outdoors or in wet areas can lead to premature corrosion. The right choice of finish ensures durability and compliance.

🌧️ Real UK Scenario: Solar panel struts in a coastal installation near Blackpool rusted after one winter due to the use of BZP instead of hot-dip galvanised (HDG) or stainless steel.

🌦️ Indoors: BZP is fine for dry, non-corrosive conditions.
🏭 Outdoors / Industrial: Use HDG or Stainless Steel (A4/316).
💼 Consult BS EN ISO 12944 corrosion protection guidelines.

✅ Pro Installation Tips

🧰 Torque bolts to manufacturer recommendations (e.g. 20Nm for M10).
🪛 Use spring nuts for ease of assembly on vertical surfaces.
📋 Keep a record of support locations and load assumptions.
⚙️ Use end caps for a clean, safe finish.
📦 Store components off the ground in dry conditions before use.

❓ Frequently Asked Questions

Do I always need back plates?: Yes — especially on wall-mounted brackets or when fixing into blockwork or plasterboard.
Which finish is best for rooftops?: Hot-dip galvanised or A4 stainless steel, depending on exposure to salt, UV, or chemicals.
How far apart should fixings be?: Every 600mm–800mm is typical for most support systems, but refer to load charts for specifics.

For official guidance, see the HSE’s installation safety guide.