Fixing steelwork to concrete, brick and timber

A steel base plate does not make a connection safe. The load must travel from the steelwork, through each anchor and into material capable of carrying it. If the last material is only screed, brick facing or a deck board, the connection stops there. This guide helps you gather information before ordering railings and balustrades. It is not an anchor design.

The authority is the designed connection

Anchor type, diameter, embedment, spacing, edge distance, hole cleaning, tightening torque and base-plate thickness form one tested and calculated system. The imposed action, lever arm and exposure decide the connection, not the steel item's weight.

The structural engineer defines the actions and checks the supporting structure. For concrete, EN 1992-4 provides the design framework for fastenings. The selected anchor's current European Technical Assessment, often called its ETA, and the manufacturer's installation instructions govern where and how that product can be used. If a generic detail conflicts with either source, the calculation and approved product data win.

Identify the real substrate

Do not identify a wall from its visible face. Render can hide solid brick, perforated units, aerated concrete or a thin skin in front of a cavity. A tiled landing can hide floating screed over insulation. A timber terrace can be boards over joists running the wrong way.

1. Use drawings, inspection holes or a competent survey to identify structural material and thickness.
2. Record every non-structural layer between the plate and that material.
3. Locate free edges, joints, voids, reinforcement, services and waterproofing.
4. State whether the connection is indoors, outdoors, wet, coastal or exposed to de-icing salt.
5. Do not fabricate the hole pattern until the anchor layout has been checked.

Reinforced concrete

Sound reinforced concrete is usually the most predictable substrate, but the word concrete is not a specification. Strength, member thickness, cracked or uncracked condition, reinforcement, edge distance and damage all matter. A slab edge or stair nosing is sensitive because an expanding anchor near a free edge can split off concrete.

Mechanical anchors develop force through expansion, undercutting or bearing. Bonded anchors use resin along the drilled hole. Neither family is automatically stronger or safer. A bonded system may suit awkward geometry only when its approval covers the concrete condition, hole orientation, temperature and service environment.

Scan for reinforcement and services before drilling. Do not cut reinforcement to make a plate fit. Moving a hole on site changes the plate's force distribution and needs approval from the connection designer.

Solid brick and solid masonry

Solid brick varies from hard to soft and fractured. Anchor into the masonry unit only where the chosen product's ETA and design require it, with the specified distance from unit edges and joints. Mortar is not a substitute unless the fixing system is explicitly approved for it.

Expansion anchors can burst weak units or masonry near an edge. Bonded anchors may reduce expansion stress, but resin does not repair poor masonry. On uncertain walls, the engineer may specify representative proof tests and the acceptance criteria.

Perforated brick and hollow block

A drilled hole in perforated masonry passes through thin webs and voids. A concrete wedge anchor can crush the webs without reliable warning. Approved bonded systems often use a perforated sleeve that holds resin around the fixing, but only when the ETA lists the actual unit and method.

Record the exact unit if possible, wall thickness and hole direction. Drilling mode matters because hammer drilling can break thin webs in some units. Follow the anchor manufacturer's instructions rather than a universal rule.

Aerated concrete block

Aerated concrete is light and porous. Standard concrete wedges and unspecified resin are not a design. Use a system specifically assessed for aerated concrete, with the material class and method within its approval. Plate area, anchor number and edge distance may require a larger bracket or a frame reaching stronger structure. Such frames belong with steel structures.

Structural timber

Fix to joists, beams, studs or engineered timber identified by size, grade and direction, not to decking, floorboards, plywood facing or cladding alone. The timber designer checks withdrawal, shear, splitting, moisture and the load path through the supports. A bolt near a joist end can split it along the grain.

Through-bolts with suitable washers or a designed plate on the far side are inspectable where access exists. Structural screws can work without through access only in arrangements covered by their technical data. External timber movement may require inspection and retightening.

Floating screed, insulation and waterproofing

Screed carries floor finishes and is often separated from the structural slab by insulation. It cannot be the anchoring material for a guard. A rigid spacer or plinth may pass through non-structural layers to the slab without crushing them. On balconies and terraces, each penetration is also a waterproofing detail that its designer must approve before drilling.

Side fixing can move penetrations away from the walking surface, but changes the lever arm and still needs a designed substrate. Decide the mounting face on the drawing, including for stairs and access.

Installation is part of the design

• Use the drill diameter and method specified for the selected anchor.
• Clean the hole with the prescribed brush and air sequence. Dust can control a bonded fixing's failure.
• Observe cartridge condition, mixing, working time and cure at the actual substrate temperature.
• Set the approved embedment and specified torque with calibrated equipment where required.
• Record the product, batch, installer, hole position and required proof tests.
• Do not load the connection before the specified cure and installation acceptance.

What must be settled before fabrication

Ask for the approved hole layout before steel is cut, and give the installer the exact anchor schedule rather than a product family. Whether anchors or instructions are supplied with an order is a commercial detail to confirm in the FAQ and order confirmation.