Base for welding 40x40/85x85mm, Raw, S235

The Strofix base for welding 40×40 / 85×85mm, RAW, S235 is a carbon-steel (S235) square base plate for the 40 × 40 mm square railing post tube. The plate measures 85 × 85 mm and is 5 mm thick (h), supplied in a raw black carbon-steel finish. The post tube is attached by welding.

This is the carbon-steel (S235) version of the 85 × 85 mm square base plate — the most economical of the three grade options. Unlike the AISI 304 and AISI 316 stainless versions, S235 is mild carbon steel and is not corrosion-resistant on its own; it must be painted, galvanised, or otherwise coated for outdoor or exposed use, and is well suited to interior installations or fabricated assemblies that will be finished and coated. At 5 mm thick it sits between the 4 mm AISI 304 and 6 mm AISI 316 versions. The raw surface is standard for base plates concealed by a decorative cover after installation.

Use cases:

• Economical floor mounting of 40 × 40 mm square railing post tubes
• Interior or to-be-coated installations where stainless steel is not required
• Fabricated steel assemblies finished and painted/galvanised on site
• Square base plate matching a square post profile for clean alignment
• Welded square post bases concealed by a decorative cover

FAQ

What post tube does this base plate fit?

The 40 × 40 mm square post tube — the square railing post profile in the Strofix range.

What is S235 steel?

S235 is structural mild (carbon) steel. It is not corrosion-resistant on its own and must be painted, galvanised, or coated for outdoor or exposed use. It is the lowest-cost grade option for this plate.

How does this compare to the stainless versions?

The AISI 304 (4 mm) and AISI 316 (6 mm) versions are stainless and corrosion-resistant for outdoor use. This S235 version (5 mm) is carbon steel at a lower price, suited to interior or coated applications.

What are the plate dimensions?

85 × 85 mm with 5 mm thickness (h). A square plate matches the square 40 × 40 mm post profile.

How is the post tube attached?

The post tube is welded to the base plate using TIG or MIG welding.

Why is the surface raw?

The raw finish is standard for base plates that are concealed by a decorative cover after installation; with S235, the plate should also be coated for corrosion protection.

About Base & Clamp Fastenings

A base or clamp fastening is a stainless-steel plate or bracket that anchors a railing post to the building structure, forming the structural foundation of the balustrade. Bottom fastenings bolt to the top of a floor slab, deck or beam, while side fastenings bolt to the vertical face of a fascia, edge beam or wall. Assembly clamps grip an existing tube or post without welding, and assembly plates provide a flat mounting surface for auxiliary connections.

Strofix supplies 18 base and clamp products for Ø42.4 mm round pipe and 40×40 mm flat-sided square posts, with plate diameters from Ø80 to Ø100 mm (round) and plate dimensions from 80×80 to 135×56 mm (rectangular/square), in satin or raw-surface stainless steel with AISI 304 and AISI 316 options.

Screw-hole configurations include 2, 3 and 4-hole variants. The correct fastening depends on mounting orientation, post profile, plate size, number of screw holes and the required surface finish.