What are render beads?

Render beads are metal or PVC profiles that provide clean, straight edges to external render. Corner beads protect and define external corners. Stop beads create a neat edge where render meets another material (windows, doors, different finishes). Bellcast beads sit at the base of render to throw water away from the wall.

What is a bellcast bead?

A bellcast bead (or drip bead) is fitted at the bottom edge of external render, typically just above the DPC line. It has a small outward curve that directs rainwater away from the wall face, preventing staining and damp issues. Bellcast bead runs horizontally along the full width of the rendered area.

How do I fix render beads to the wall?

Render beads can be fixed with stainless steel nails or screws at approximately 300mm centres (3 fixings per metre). For masonry substrates, use masonry nails or plugs and screws. Always use stainless steel fixings to prevent rust staining through the render. Some beads can be bedded into a scratch coat of render.

What length do render beads come in?

Standard render beads are available in 2.4m and 3.0m lengths. The 2.4m length is most common and matches standard sheet material heights. For walls taller than the bead length, beads can be butted end-to-end — ensure a clean, straight joint.

Do I need corner beads on external render?

Yes, corner beads are essential on all external corners. They provide a straight, plumb edge and protect the vulnerable corner from impact damage. Without corner beads, external corners will crack, chip and look untidy. Use stainless steel or PVC beads suitable for external use — galvanised beads can rust.

TradeCalculator.co.uk

External Render Bead Calculator — Corner, Stop & Bellcast

Calculate corner bead, stop bead and bellcast bead quantities for external rendering. Includes fixing counts.

Wall Width

Total width of wall being rendered

Wall Height

Height of render from bellcast to soffit

External Corners

Number of external corners to bead

Stop Ends

Where render stops at windows, doors etc.

Bellcast Run Length

Total horizontal length of bellcast bead

Bead LengthStandard length of beads to purchase

How We Calculate This

This calculator works out the quantity of render beads needed for external rendering, based on wall dimensions, number of corners and stop ends.

The formula

Corner beads: Number of corners × Wall height ÷ Bead length
Stop beads: Number of stops × Wall height ÷ Bead length
Bellcast bead: Total run length ÷ Bead length
Fixings: Total bead length × Fixings per metre

All quantities are rounded up to whole beads, as you cannot buy part-lengths. Fixings are calculated at 3 per metre (300mm centres) by default.

Frequently Asked Questions

Related Calculators

Plaster Coverage Calculator

Calculate how many bags of plaster you need for any wall or ceiling area.

Skim Coat Calculator

Calculate multi-finish plaster needed for skim coating walls and ceilings.

Rendering Calculator

Calculate sand and cement quantities for external rendering.

Dot and Dab Calculator

Work out adhesive needed for dot and dab plasterboard fixing.

Last updated: March 2026

All calculations are estimates. Verify with your supplier.