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on-site work

FRP Installation and Fasteners

GRP and FRP profiles are not welded. A system is built with bolted joints, structural bonding, or both together. The right cut, the right hole and a sealed cut face directly set the life of the material.

Describe your project, get a quote Installation checklist

↳ if you cut it, seal it — the one golden rule on this page

Composite is not joined like metal

In steel the familiar reflex is welding: cut, tack, stand it up. With composite there is no such option. A GRP or FRP profile cannot be melted and fused; the joint is either mechanical, with bolts, or chemical, with structural adhesive, or both at once. That is not a disadvantage, only a different discipline. Applied correctly it gives a system that can be taken apart, extended and corrected easily on site.

Another difference with composite is direction sensitivity. In a pultruded profile the fibers run mainly along the length; the material is very strong lengthwise and more sensitive across. That is why hole position, edge distance and clamping force are set by the logic of the composite rather than by habits carried over from metal. how a GRP profile is made makes decisions on site easier too.

method 01

Bolted joints

The method used most on site: it is fast, carries load immediately, can be taken apart and can be inspected after installation.

Strengths

No cure to wait for; it carries load the moment it is tightened
Removable — maintenance, changes and extending the system are easy
Open to correction and fine adjustment on site
Visually inspectable; loosening can be spotted
It can be applied in cold and damp weather too

What to watch

Leave edge distance: if the hole sits too close to the end of a member, the edge can tear under load. Position the hole far enough from the edge and from other holes.
Use a large washer: the washer spreads the clamping force over a wide area and stops the surface being crushed. A small washer leaves a mark in composite.
Do not over-tighten: composite does not get stronger the harder you tighten it, the way metal does. Apply controlled torque; if the seat area is crushed the joint loosens.
Hole size: do not force the bolt through. The hole must be clean and sized to the bolt diameter; driving it in starts a crack.
Locking nut: on sites with vibration, a locking nut or lock washer is preferred against loosening.
Sealing after drilling: every hole drilled is a new cut face — it must be sealed with resin.

method 02

Bonded joints

It spreads load over a wide area, does not weaken the section with holes and creates a sealed surface. In return it asks for patience: surface preparation and cure time.

Strengths

Load is distributed over the whole bonded area rather than at a single point
With no hole drilled, no fiber is cut and the strength of the section is preserved
No new route is created for water and chemicals
It gives a smooth finish with nothing protruding
It allows different geometries to be joined

Application sequence

1 · Surface preparation: the bonding face is abraded to a matt finish; a glossy surface weakens adhesion.
2 · Cleaning: dust, grease and moisture are removed completely; the cleaner recommended by the adhesive manufacturer is used.
3 · Mixing: for two-component products the mixing ratio and mixing time follow the product instructions.
4 · Application: applied within the pot life, at sufficient thickness and without voids.
5 · Support: the parts are held fixed with clamps or props for the cure time and not moved.
6 · Cure: temperature and humidity must be within the range the product states; cold lengthens the cure.

↳ on critical and load-bearing joints, bolts and adhesive are used together

site work

Cutting and drilling rules

A GRP or FRP profile can be cut and drilled on site — one of the most practical things about composite. But glass fiber is abrasive; working with a blunt bit or the wrong speed makes the job harder and starts cracking and delamination at the edges.

Cutting

A diamond or carbide tipped, fine-toothed cutter is preferred
High speed, low feed — cut without forcing the material
The profile is clamped firmly; vibration cracks the edge
Mark the cut line and keep the cutter square
Burrs are lightly removed after cutting

Drilling

Use a sharp bit; a blunt bit burns and tears the material
Put a backing block behind the face — it prevents break-out on exit
Press at a steady, moderate speed; do not force the drill
For large diameters, drill a pilot hole first
Clean the edges after drilling

Safety at work

A dust mask is used against glass fiber dust
Safety glasses and gloves are essential
Long sleeves prevent skin irritation
Work with dust extraction where possible and ventilate the area
Afterwards the area is cleaned by vacuuming rather than sweeping

the golden rule

Seal the cut face with resin

When the profile is made, its outer surface is protected by a surface veil and a resin layer. But when you cut it to length or drill into it, a new face appears without that protection: fiber ends are exposed. That face is the weakest point of the whole system against corrosion.

Water, salt or chemicals can travel from that open face to the fiber-resin interface. The solution is simple and cheap: every cut and drilled face is sealed with a coating from the same resin family as the profile. It is brushed on and left to dry; a second coat is applied if needed.

End faces of length cuts
Bolt holes and the inner walls of holes
Square and angled cut faces
Penetrations drilled later and enlarged holes
Areas that have been ground or dressed

↳ five minutes of work makes the difference of years

material selection

What should the fastener be?

Composite does not rust — but if the bolt holding it rusts, the system still weakens. Fixing a corrosion-resistant profile with an ordinary bolt is one of the most expensive mistakes there is. The fastener is chosen for the environment the profile works in.

Stainless steel — recommended

Our standard choice is a stainless steel fastener. It keeps working for a long time in moisture, chemicals and outdoor conditions; in marine and salty environments, stainless grades with higher corrosion resistance are preferred.

↳ bolt, nut and washer must come from the same family

Composite (GRP) fastener

Used where full electrical insulation is required or metal contact is not wanted at all. Clamping force is limited; the torque value must be applied with particular care.

↳ for sites where the insulation must be unbroken

Galvanized or black bolts — avoid

Galvanized coating gets scratched during installation and rusts from the cut end. Outdoors and on wet sites this becomes the first weak link. Not recommended except for short-lived, temporary work.

↳ a rust stain leaves a mark on a composite surface too

Completing the fastener set

Large-area washer: spreads the clamping force and prevents surface crushing.
Locking nut or lock washer: prevents loosening on sites with vibration.
Do not mix metals: to prevent galvanic corrosion, bolt, nut and washer must be chosen from compatible materials. The composite itself is non-conductive, which gives the advantage of breaking the chain; it is the metal parts that build it.
Anchor side: for fixing into concrete or steel structure, the anchor material must be chosen with the same corrosion logic.

notes from site

Installation tips

Dry-fit first: place all parts without tightening, check dimensions, then tighten in order. That way tolerances do not accumulate at one point.
Tighten in sequence: work in a balanced order rather than end to end; the member will not distort.
Do not drag on the ground: pulling the profile along the floor damages the surface veil. Carry it with two people.
Long and light: the profile is light but long; held at one point it sags. Support it at two points.
Storage: store on flat ground, on spaced supports and raised off the floor; do not leave it in direct sun for long periods.
Expansion allowance: on long runs, allowance is left at joints for length change with temperature.
Measurement mistakes do not forgive: measure twice before cutting. The length you cut off does not come back.
Do not throw away offcuts: short pieces can be used as brackets, packers and supports.

Post-installation checklist

Have all cut faces and holes been sealed with resin?
Were the bolts tightened to controlled torque, is there any crushing mark?
Were large washers and locking nuts used?
Are the fasteners stainless, is there any mixed material?
On bonded joints, is the cure time complete?
Are there any loose or moving elements on handrails and platforms?
Have cutting burrs been removed, is any sharp edge left?
Has the area been cleaned and the glass fiber dust collected?

↳ the first check as soon as installation ends, the second at the end of the first season

Maintenance and service life →

next step

Send your section and we will work out the installation detail together

Describe your dimensions, the joint locations and the surface you are fixing to; we will settle the right profile, fastener and installation detail together. Dimensions are enough for a quote.

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