How do I choose between Catnic and IG lintels?

Both Catnic and IG Lintels are reputable UK manufacturers with similar product ranges. Catnic (Tata Steel) and IG Lintels both produce pressed steel lintels to BS EN 845-2. Choice often comes down to local availability and price. Both provide load/span tables, technical support, and BBA certification. Check with your builders' merchant for stock.

What bearing length does a steel lintel need?

Steel lintels require a minimum bearing of 150mm at each end for openings up to 1200mm, and 200mm for wider openings per manufacturer recommendations. The bearing must be on solid masonry — not on aerated blocks unless a padstone is used. The lintel length = opening width + 2 × bearing length.

What deflection limit applies to steel lintels?

Steel lintels supporting masonry must limit deflection to span/325 to prevent cracking in the brickwork above. This is more stringent than the standard L/360 for beams supporting floors. Manufacturers' load tables already account for this deflection limit, so if you select from their tables, the deflection check is built in.

Can I use a steel lintel above a garage door opening?

For garage openings (typically 2.1-4.2m wide), standard pressed steel lintels can span up to about 3.6m. For wider openings, heavy-duty (HD) lintels or combination lintels may be needed. For very wide openings (over 3.6m), a structural steel beam (RSJ) may be more appropriate. Check the manufacturer's load tables for your specific span and loading.

Do steel lintels need any special treatment or protection?

Most steel lintels come pre-galvanised with a Z275 zinc coating, which provides adequate corrosion protection when built into a wall. No additional treatment is normally needed. However, if a lintel is cut on site, the cut ends should be painted with cold galvanising spray. In aggressive environments (coastal, industrial), stainless steel lintels may be specified.

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Steel Lintel Calculator — Catnic/IG Selection by Opening Width

Select the right steel lintel for your opening width. Covers Catnic and IG type lintels for cavity walls and single-leaf walls, with deflection check to L/325.

Opening Width

Clear width of door or window opening

Cavity Width

Width of wall cavity

Leaf Support

Which wall leaves the lintel supports

Load Type

Type of load above the lintel

How We Calculate This

This calculator helps select the correct steel lintel for a masonry opening based on the opening width, cavity size, leaf support, and load type.

Selection process

Opening width: Determines the clear span the lintel must bridge
Cavity width: 50-150mm — lintel must match the cavity
Leaf support: Both leaves (cavity lintel) or single leaf (inner/outer only)
Load type: Standard masonry, heavy loading, or point loads

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.