OO GAUGE · PLANNING
How much space does an OO layout need?
The smallest Hornby setrack circle, using 1st radius curves, needs a space 771mm across, including the width of the track. Every other layout grows from there. The table below gives the exact footprint of circles and ovals at each radius, and which common boards they fit.
Footprints at every radius
Sizes include the 29mm width of the track, measured from outside edge to outside edge. "Fits" means the track fits the board with nothing to spare at the tightest edge, so allow a little more in practice.
| Layout | Footprint | 4 × 3 ft | 6 × 4 ft | 8 × 4 ft | Door |
|---|---|---|---|---|---|
| R1 circle | 771 × 771mm | Fits | Fits | Fits | – |
| R1 oval, 168mm straights | 939 × 771mm | Fits | Fits | Fits | – |
| R1 oval, 335mm straights | 1106 × 771mm | Fits | Fits | Fits | – |
| R1 oval, 670mm straights | 1441 × 771mm | – | Fits | Fits | – |
| R2 circle | 905 × 905mm | Fits | Fits | Fits | – |
| R2 oval, 168mm straights | 1073 × 905mm | Fits | Fits | Fits | – |
| R2 oval, 335mm straights | 1240 × 905mm | – | Fits | Fits | – |
| R2 oval, 670mm straights | 1575 × 905mm | – | Fits | Fits | – |
| R3 circle | 1039 × 1039mm | – | Fits | Fits | – |
| R3 oval, 168mm straights | 1207 × 1039mm | – | Fits | Fits | – |
| R3 oval, 335mm straights | 1374 × 1039mm | – | Fits | Fits | – |
| R3 oval, 670mm straights | 1709 × 1039mm | – | Fits | Fits | – |
| R4 circle * | 1173 × 1173mm | – | Fits | Fits | – |
| R4 oval, 168mm straights * | 1341 × 1173mm | – | Fits | Fits | – |
| R4 oval, 335mm straights * | 1508 × 1173mm | – | Fits | Fits | – |
| R4 oval, 670mm straights * | 1843 × 1173mm | – | – | Fits | – |
Leave a margin at the edge
A layout that fits exactly leaves trains hanging over the edge of the board on the curves, and anything that derails has nowhere to go. We'd leave at least 50mm between the track and the edge of the board, more on a layout that children will use.
Why an oval won't fit on a door
An old internal door makes a cheap, flat baseboard, but a common UK internal door is 762mm (2ft 6in) wide, and the smallest Hornby circle needs 771mm. Wider doors exist, so measure yours. A door suits a shunting layout instead: see the door shunting plan.
Getting more on a 6 × 4 board
A 6 × 4 board takes a 1st radius oval with long straights, two loops side by side as double track, or a single 2nd radius oval for bigger locos. Ready-made examples: Starter oval on a 6 × 4 board, Double oval for two trains and 2nd radius oval for bigger locos.
* 4th radius figures are still being double-checked against Hornby's own measurements.