Common Limitations of Using Through Bolts in Concrete and Masonry

Posted: September 05, 2025

Categories: News

Introduction

Through bolts are one of those fasteners you’ll see everywhere in the construction world. Simple in design, strong in application, and usually trusted to hold heavy-duty brackets, structural plates, or machinery bases in place. If you walk around a commercial warehouse or even a modest car park, chances are that some of the steelwork above your head is secured with through bolts.

But while they’ve earned a reputation for reliability, through bolts aren’t perfect. In fact, depending on the material you’re working with—concrete, masonry block, or brick—they bring along some built-in limitations that installers and designers can’t afford to ignore. This post digs into those weak points, with a mix of technical detail and practical site wisdom, and also shares a few alternatives from the perspective of a global fastener supplier like Qewitco Fasteners, who has been working with both standard and customized anchoring systems since 2004.

Common Limitations of Through Bolts

While through bolts offer a robust and widely used fastening solution, their effectiveness is heavily dependent on correct installation and appropriate application. The following outlines key limitations and common pitfalls that can compromise both immediate performance and long-term reliability.

Installation-Related Limitations

Inadequate edge distance

One of the most common mistakes with through bolts is installing too close to an edge. The general rule is a minimum of six times the bolt diameter as clearance. For example, if you’re working with a 12 mm bolt, you want at least 72 mm of solid concrete before you hit the edge. Skip this rule and the tightening torque can easily crack off a chunk of concrete. We’ve seen it happen on precast stairs where someone rushed a fixing—half a step broke away, leaving a very unhappy site manager.

Incorrect alignment

Through bolts like to sit straight. If you drill at a slight angle or insert the anchor skewed, the expansion mechanism doesn’t grip evenly. This reduces load capacity and, worse, can twist the attached steelwork. I once heard a fitter joke that “angled bolts are great if you want your railing to lean like the Tower of Pisa.” Not recommended.

Poor anchoring location

Placing a through bolt in hollow brick or near a mortar joint is a recipe for frustration. The expansion force needs a dense substrate, otherwise the anchor just spins or pulls through. This is one reason many tradespeople prefer chemical anchors in hollow masonry.

Geometric and Material Constraints

Access to both sides

Through bolts, by design, need to pass entirely through the fixture and into the material. That means you need access from the front for the bolt head and space behind for the expansion cone. If you’re working with a solid wall or a closed cavity, through bolts are simply off the table.

Unsuitable for thin substrates

Thin slabs or fragile masonry can’t provide enough embedment depth. If you’re trying to fasten something heavy to a 60 mm brick wall with a through bolt, you’ll quickly learn that the expansion stresses are more likely to break the brick than hold your fixture.

Fixing Performance and Long-Term Behavior

Load relaxation

A less obvious limitation is load relaxation. Even if you torque a through bolt perfectly on day one, the clamping force can drop over time—sometimes by 40–50%. This happens due to micro-cracking in the substrate or long-term creep under load. In practice, it means that handrail that felt rock-solid when installed may rattle slightly after a year of heavy use.

Risk of breakout or bearing failure

Under high loads, especially in masonry block, the expansion cone can cause breakout of the block face. Engineers refer to this as “cone failure” or “splitting.” You don’t need to remember the jargon—just picture half a brick breaking loose when too much load is applied.

Torque sensitivity

Through bolts rely on precise torque to achieve their rated strength. Too little torque and the anchor doesn’t expand enough; too much and you risk stripping the threads or crushing the substrate. It’s not a forgiving system. Experienced installers will use a calibrated impact wrench, but on real job sites, a lot of tightening is done “by feel”—which explains why results can vary.

Code and Design Model Limitations

Limited coverage in standards

Unlike chemical anchors or cast-in studs, through bolts don’t always have explicit code language in masonry applications. For example, the ACI 318 code (widely used in concrete design) is more conservative on shear values, while the TMS masonry code tends to over-predict breakout strength. The net result is confusion for engineers trying to design conservatively but without over-specifying costly alternatives.

Difference between lab data and real life

Test data in controlled conditions often show better performance than what happens on a windy scaffold tower or a dusty site. It’s no surprise—dust in the hole, uneven drilling, and installers in a hurry can reduce capacity far below the “catalogue values.” This gap between the lab and the job site is one of the persistent headaches with through bolts.

Alternatives and Mitigation Strategies

Using chemical anchors

When edge distance is limited or the substrate is hollow, chemical anchors are usually the better choice. They bond into the drilled hole without expansion forces, which means less risk of cracking and often higher load ratings. Yes, they cost more and require curing time, but they solve problems that through bolts can’t.

Proper installation practices

If you stick with through bolts, discipline matters. Drill the right diameter hole, blow out the dust (compressed air helps), keep to the recommended edge distance, and use a torque wrench. It sounds tedious, but every missed step cuts into performance. At Qewitco, we often advise clients with high-volume installations to run on-site training sessions or at least provide torque charts with the supplied fasteners.

Conservative design approach

When design codes don’t give clear guidance, it’s smart to lean conservative. Assume lower capacities and, where possible, specify additional anchors to share the load. It’s always cheaper to add two more bolts than to deal with a failure after handover.

Conclusion

Through bolts are dependable workhorses in construction, but they aren’t a one-size-fits-all solution. Their limitations—whether it’s edge distance, torque sensitivity, or long-term relaxation—need to be factored into both design and installation.

At Qewitco Fasteners, we’ve supplied through bolts, shield anchors, concrete screws, and chemical anchor systems across Europe, Asia, and beyond. Our experience is that no single product solves every fixing challenge, which is why we carry over 30,000 product lines, including bespoke fasteners for non-standard applications.

If your next project involves concrete or masonry fixings, remember that the choice of anchor is as much about the material as it is about the load. Sometimes a through bolt will do the job perfectly. Other times, it’s better to step back, look at the substrate, and consider alternatives. After all, the true cost of an anchor isn’t just its price per unit—it’s whether it holds when it matters most.

Looking for reliable through bolts, chemical anchors, or custom fastening solutions? Contact Qewitco today and get expert advice for your next project.

FAQs

Q1. Can through bolts be reused once removed?
Generally no. Once a through bolt has expanded in the substrate, it loses its rated holding capacity if reinstalled. For removable solutions, mechanical concrete screws or Qewit’s Lightning Bolts are better choices.

Q2. How do I prevent concrete from cracking when using through bolts?
Keep a minimum edge distance (around 6 × bolt diameter), drill straight, and avoid overtightening. If edge space is limited, switch to a chemical anchor.

Q3. Are stainless steel through bolts worth the higher cost?
Yes, if your project is outdoors or in a corrosive environment. Stainless steel versions resist rust and extend service life, which saves money on maintenance and replacements down the line.