Fixing failures are one of the most common problems on construction sites and home projects. When a screw spins in brick, when an anchor works loose from a wall or when a bolt pulls out under load, it slows down work and often forces the installer to start again. In more serious cases, failures damage the surrounding structure or compromise safety.
Most failures occur not because the fixing is poor quality but because something about the installation process, substrate or load conditions does not match what the fixing was designed for. This detailed guide explains the specific reasons fixings fail, the early warning signs and how tradespeople and competent DIYers can prevent issues long before they happen.
1. Incorrect fixing selection for the substrate
Fixings behave very differently depending on what they are installed into. A fixing that performs perfectly in concrete may fail almost immediately when used in thermalite block or old clay brick.
Read more: How to choose which fasteners you need for your project
How substrate issues cause failures
Solid concrete
Concrete is generally strong, but its density varies. High strength concrete resists drill penetration, so installers sometimes use worn drill bits or force the drill. This produces out-of-round holes that prevent wedge or sleeve anchors from expanding correctly. If the cone cannot expand uniformly, the anchor may slip under tension or vibrate loose.
Old brickwork
Older buildings often contain handmade bricks, soft lime mortar and internal voids. When a standard plug expands inside a weak brick, the wall can crumble instead of gripping the plug. This leads to spinning fixings and early pull-out under even light loads.
Thermalite and aerated blocks
These blocks have a high air content and crumble easily. When someone uses a traditional red or brown wall plug in aircrete, the expansion force causes the block to fracture internally. The fixing might feel tight at first but will fail as soon as the load is applied.
Timber
Using the wrong thread type for the timber leads to inadequate bite. Fine thread screws strip easily in softwood. In hardwood, coarse threads can split the timber if no pilot hole is used, causing poor engagement.
Steel
Self-drilling screws are designed for specific gauges. Using a self-drilling screw meant for 1.5 mm steel on a 4 mm plate burns the drill point instantly. Once the point burns, the screw no longer cuts and simply spins, creating heat and damaging the material.
How to prevent substrate-related failures
• Identify the substrate before selecting the fixing
• For old or weak brickwork, use frame fixings, resin anchors or long concrete screws
• For concrete, select wedge anchors, throughbolts or concrete screws matched to tested loads
• For aircrete, use specialist fixings with low expansion pressure
• For timber, match thread type and use the appropriate pilot hole
• For steel, choose the correct self-drilling screw point type for the steel thickness
The more precisely the fixing is matched to the material, the longer and safer the installation will be.
2. Incorrect pilot hole size, depth or drilling technique
Even excellent fixings fail if the hole is not prepared properly. Drilling errors account for a large percentage of failures on site.
Common drilling mistakes that lead to failure
Oversized holes
If the drill bit wears down or wobbles during drilling, it creates a hole that is too large. Expansion anchors depend on contact with the substrate. Even 0.5 mm oversize can reduce holding capacity significantly.
Undersized holes
Concrete screws require precise diameter holes. Too small and the screw cuts too aggressively, damaging the concrete. Too large and the threads cannot bite correctly.
Shallow holes
If the embedment depth is insufficient, the fixing bottoms out. Many installers assume the hole is deep enough but have not accounted for dust buildup at the bottom. This prevents full insertion and reduces load capacity.
Poor hole quality
A cheap or blunt drill bit can create a rough, funnel-shaped hole. Anchors can only expand fully in a clean cylindrical hole. A tapered hole reduces tension performance dramatically.
How to drill correctly for maximum fixing performance
• Use the exact drill bit diameter specified by the manufacturer
• Drill 5 to 10 mm deeper than the embedment depth required
• Clean out dust using a brush, vacuum or blower
• Use SDS bits for concrete and HSS bits for metal
• Avoid pushing too hard when drilling into masonry
• Check the hole periodically if drilling into inconsistent substrates
Good drilling technique often matters more than the brand of the fixing used.
How to test a fixing before committing to the full installation
Before installing multiple fixings, it is good practice to carry out a simple test on the first hole to confirm the substrate and fixing are working together as expected. Many failures are avoided by checking the performance of just one fixing before committing to the full pattern.
Start by drilling a clean test hole and verifying the embedment depth using a depth gauge or the marked shaft of the drill bit. After cleaning out the dust, install the fixing and tighten it gradually so you can feel how the substrate responds. If you are installing a mechanical anchor, monitor how quickly resistance builds. A fixing that reaches full torque too early or too late often indicates an issue with hole size or material integrity.
3. Over-torquing or under-torquing fixings
Fixings have ideal torque ranges. Too much or too little torque quickly leads to failure.
Over-torquing issues
• Threads strip out of timber, leaving the screw spinning
• Plugs collapse internally in masonry
• Wedge anchors expand too aggressively and crack the hole
• Bolts stretch and weaken, especially in high load applications
Under-torquing issues
• Anchor sleeves do not expand fully
• Screws remain slightly loose and move under load
• Vibration causes early failure in fixings that depend on tight clamping forces
How to achieve correct torque
• Use tools with torque control when possible
• For impact drivers, choose lower settings for timber and plugs
• Tighten concrete anchors slowly to allow controlled expansion
• For timber screws, stop when the screw seats firmly without crushing the wood
Correct torque protects both the fixing and the substrate.
4. Corrosion and environmental exposure
Fixings fail early when the material cannot withstand the environment they are installed in.
How environment causes failure
Rust formation
Zinc plated fixings corrode quickly in outdoor conditions. Rust expands as it develops, weakening the screw shaft and causing staining around the fixing.
Coastal environments
Salt air penetrates coatings rapidly. A2 stainless often lasts, but A4 stainless is preferred for maximum marine protection.
Chemical exposure
Factories, industrial buildings and farms can expose fixings to chemicals, ammonia or moisture that corrode steel quickly.
Temperature fluctuations
Repeated heating and cooling cycles can loosen fixings that rely on friction or expansion.
Choose fixings that match environmental conditions
• Use stainless steel outdoors or near coastal areas
• Choose hot dipped galvanised fixings for general external construction
• Use coated screws for decking and exterior timber
• Select A4 stainless in marine or acidic environments
• Consider chemical anchors when mechanical fixings may degrade
5. Weak, damaged or unpredictable substrates
Often the substrate is the problem rather than the fixing.
Failure examples
• Cracked concrete cannot hold expansion anchors
• Perished mortar in brickwork causes plugs to spin
• Thermalite blocks crush under even moderate tension
• Old walls contain voids, soot pockets or mixed materials
Solutions for compromised substrates
• Resin anchors provide high strength with minimal expansion force
• Longer fixings can reach more stable material deeper in the wall
• Timber battens can be used to create a stable fixing surface
• Multiple smaller fixings can distribute loads better than one large anchor
Understanding point loads and distributed loads
Fixings often fail not because the load is too heavy overall but because too much force is concentrated on a single point. Point loads place significant stress directly at one fixing location, which can exceed the pull-out or shear strength of even high quality anchors. This is common when a shelf bracket, gate hinge or machinery mount relies on a single fixing to take the majority of the weight.
Distributed loads behave very differently. When weight is spread across multiple fixings, the force applied to each individual anchor is much lower, which increases overall stability and reduces the chance of localised failure. For example, a large wall-mounted cabinet supported by only two fixings is much more likely to pull out of brickwork compared to one supported by four or six properly spaced anchors.
Lever forces also play a role. The further the load sits from the wall or fixing point, the greater the twisting force applied to the fixing. This is why cantilever brackets and long arm supports require careful fixing design. Understanding how loads distribute across your fixings helps prevent structural failures and ensures safer, longer lasting installations.
Choosing the right drill bit and drilling speed
The performance of a fixing depends heavily on the quality of the hole that is drilled. Using the wrong drill bit or drilling at the wrong speed can create irregular or oversized holes that weaken the fixing immediately. For concrete and masonry, SDS hammer drills with carbide tipped bits provide clean, consistent holes. Using a worn bit creates oval holes that prevent expansion anchors from gripping.
Drilling speed is equally important. High RPM with excessive pressure generates heat and can glaze the sides of the hole, reducing friction. For metal, self drilling screws rely on controlled, steady pressure and medium speed to allow the drill point to cut cleanly through steel. If the drill speed is too high, the tip overheats and burns out, leaving the screw unable to penetrate.
6. Load miscalculations and dynamic forces
Fixings fail when the load exceeds what they were tested for. This is not always due to weight alone.
Common miscalculations
Shear vs tension
Many fixings handle shear loads well but not tension loads. Installing a fixing vertically when it should be installed horizontally can reduce strength dramatically.
Vibration and movement
Door closers, machinery and gates introduce repeated movement that slowly works fixings loose.
Lever forces
A fixing installed far from the load point is subjected to greater stress, which many installers underestimate.
Long-term creep
Materials under constant tension can slowly deform, causing failure months or years after installation.
How to prevent load related failures
• Check both shear and tension load ratings
• Use multiple fixings for heavier installations
• Choose fixings designed for vibration resistance
• Position fixings as close to load points as possible
• Follow manufacturer load tables rather than relying on estimates
Final installation checklist
Before committing to an installation, confirm:
• The substrate has been correctly identified
• The fixing is appropriate for that substrate
• The pilot hole is the right size, depth and quality
• Dust has been removed from the hole
• Torque settings are correct
• The fixing material suits the environment
• Load expectations match the fixing’s tested capacity
This checklist takes less than a minute and is one of the most effective ways to prevent early failure.
Protect your project with high quality fixings from Confast
For reliable fixings that perform on site, choose high quality products that match the demands of your project. Confast supplies a full range of construction fixings, fasteners and specialist tools so you can work with confidence.For reliable results on site, choose high quality fixings and expert support. Contact Confast for professional diamond drilling services or explore our full range of fasteners and fixings to get the right products for your project.