100mm Box Lintels

100mm Box Lintels for Internal Masonry Walls

A 100mm box lintel is designed to suit standard 100mm internal blockwork and is commonly used above internal door openings in loadbearing masonry walls. These steel lintels provide structural support while maintaining a clean, concealed finish within the wall thickness.

All of the 100mm box lintels in this range are British-made and suitable for domestic and light commercial construction. Manufactured in the UK, they offer shorter supply chains and consistent compliance with current Building Regulations.

Whether you need a standard-duty internal door lintel or a heavier-duty option for increased loading, we stock a full range to suit typical UK masonry construction.

Standard Duty 100mm Box Lintels

For most internal door openings in 100mm blockwork, a standard-duty 100mm box lintel is sufficient.

Options include:

• Catnic BSD100 supplied in black powder-coated finish and capable of being insulated within the core. Available in lengths from 900mm to 4800mm.
  
• Stressline SL100BOX, a cost-effective 100mm box lintel available in standard sizes up to 5100mm.
  

Always refer to manufacturer load tables before selecting the appropriate lintel duty.

Heavy-Duty 100mm Box Lintels

Where higher masonry loads are present, a heavy-duty 100mm box lintel may be required.

• Catnic BHD100 designed to carry full wet masonry loads without propping. Galvanised and powder-coated for added durability.
  
• Stressline SL100BOXHD, a high-performance, cost-conscious heavy-duty option suitable for demanding applications.
  

Heavy-duty lintels are typically specified where openings are wider or where additional floor or roof loads are present.

Extra Heavy-Duty 100mm Box Lintels

For the most demanding structural conditions:

Stressline SL100BOXXHD, made to order with approximately three-week lead time.

Extra heavy-duty lintels are generally required where structural engineer calculations specify increased load capacity.

Choosing the Right 100mm Box Lintel

Selecting the correct 100mm box lintel depends on:

• Clear opening width
• Masonry load above
• Floor or roof loads bearing onto the wall
• Whether propping is acceptable during construction
  

If you are unsure which lintel duty is required, consult the relevant load tables or speak to our team for guidance on specification, availability and lead times.