---
title: "Open Coil and Bonnell Spring Systems"
description: "Plain guide to open-coil and Bonnell spring mattresses — how they work and how they differ from pocket sprung."
url: "https://bedguide.co.uk/mattresses/open-coil-bonnell/"
category: "mattresses"
primary_entity: "open coil Bonnell mattress"
date_published: 2026-08-03
date_modified: 2026-08-03
---

# Open Coil and Bonnell Spring Systems

> Open-coil mattresses use one linked spring grid, not separate fabric pockets. The Bonnell spring is an hourglass-shaped coil tied to its neighbours with wire. Because the coils share load through the grid, movement travels across the bed more than in pocket sprung units. Open coil beds often cost less. Partner movement is usually easier to feel.

## Key facts

- Materials: steel Bonnell or continuous coils, helical lacing wire, padding and quilt layers
- Typical lifespan: 5–8 years

### Construction layers

- Open-coil spring unit: Interconnected support grid
- Insulator pad: Prevent fillings from migrating into coils

## Bonnell shape

The Bonnell coil is wider at the top and bottom and narrower in the middle.
That hourglass shape gives a steady push-back feel. Spring counts are usually a
few hundred, not thousands. The coils are larger than pocket springs — see
[spring count](/mattresses/spring-count-explained).

## Continuous coil variants

Some open-coil units use long rows of wire instead of separate Bonnell coils.
The idea is the same: one connected spring surface, not independent pockets.
Brand names in this family (for example
[Miracoil](/mattresses/miracoil-explained)) still sit under interconnected-spring
physics — judge the full mattress stack, not the trademark alone.

## Motion and roll-together

Because coils are linked together, movement travels across the unit more easily
than in [pocket sprung](/mattresses/pocket-sprung) designs. That raises
[motion transfer](/mattresses/motion-isolation) and can cause
[roll-together](/glossary/roll-together) on softer top layers.

## Where open coil still appears

- Guest beds and kids' beds where cost matters
- Some budget "hybrid" stacks with foam over open coil — check the spring type
- Traditional builds with [natural fillings](/mattresses/natural-fillings-wool-cotton-horsehair)

## Related BedGuide entries

- [Miracoil explained](/mattresses/miracoil-explained)
- [Pocket sprung vs open coil](/compare/pocket-sprung-vs-open-coil)
- [Pocket sprung construction](/mattresses/pocket-sprung)
- [Mattress–base compatibility](/care/mattress-base-compatibility)

## Frequently asked questions

### What is an open coil mattress?

An open-coil mattress uses one linked spring grid. Coils connect to their neighbours, so load and movement travel across the surface more than in pocket sprung beds.

### Is Bonnell the same as pocket sprung?

No. Bonnell coils are usually hourglass-shaped and wired together. Pocket springs sit in separate fabric pockets and move more independently. See pocket sprung vs open coil.

### Who might choose open coil?

People who want a traditional spring feel and accept more partner movement transfer. Pocket sprung or hybrids usually isolate motion better.

---

Source: https://bedguide.co.uk/mattresses/open-coil-bonnell/ · BedGuide — educational encyclopedia, no affiliate commission. Facts checked against official sources where possible; see https://bedguide.co.uk/editorial-policy. Report an error: https://bedguide.co.uk/corrections.