Part of Beekeeping
Bar spacing is the most critical measurement in top-bar hive construction, and one of the most important dimensions in any managed hive. Get it right and bees cooperate with your management — they build straight, removable combs and leave passages for inspection. Get it wrong and bees glue everything shut with propolis or build cross-comb that tears apart when you try to inspect.
The underlying concept is bee space — one of the most important discoveries in the history of beekeeping.
Bee Space: The Foundation
In 1851, Lorenzo Langstroth observed something that revolutionized beekeeping: honey bees do not fill every gap in their nest with propolis or comb. They maintain specific passageways at specific widths — passageways just large enough for two bees to pass each other back-to-back.
This “bee space” measures 6 to 9 mm (approximately ¼ inch). Gaps of this width are left open as corridors. Gaps larger than 9 mm are filled with comb. Gaps smaller than 6 mm are filled with propolis.
Langstroth designed the first movable-frame hive around this observation — by maintaining precise 6-9 mm gaps between frames and between frames and hive walls, he created a hive where frames could be slid out without tearing comb or breaking propolis seals.
Every hive design that allows inspection depends on bee space. If your bar spacing is wrong, bees will either glue bars together (gaps too small) or build comb between bars (gaps too large).
Top Bar Hive: Bar Dimensions
In a top bar hive, bees build comb hanging from the underside of each bar. The bar must be wide enough to accommodate one comb, with bee space on each side between adjacent combs.
The Critical Calculation
Natural worker brood comb has a specific width. Measuring from center to center of adjacent combs in a natural nest gives the standard spacing that bees prefer. This measurement, called “comb pitch” or simply “spacing,” is:
- Worker comb spacing: 35 mm center-to-center (in temperate races of Apis mellifera)
- Drone comb spacing: 40-42 mm center-to-center (drone cells are larger)
- Honey comb spacing: 38-45 mm center-to-center (honey comb is thicker than brood comb)
Regional variation: Asian races of Apis mellifera and other bee species may differ. Africanized bees in the tropics may build at 32-33 mm. Measure combs from established feral colonies in your region if possible.
Standard Top Bar Width
The standard top bar width is 32 mm (1¼ inches) for temperate worker-comb spacing of 35 mm. This leaves about 3 mm of bee space on each side of the comb (35 mm spacing − 29 mm comb width = 6 mm / 2 sides = 3 mm per side). Combined with the bee space on the adjacent bar’s side, the passage between combs is 6 mm — exactly minimum bee space.
In practice, many top bar beekeepers use widths from 30 to 38 mm and get acceptable results. Wider bars are easier to make. Narrower bars leave more bee space per comb (better for inspection) but may encourage bees to build wider comb that bridges to adjacent bars.
Practical Bar Width Options
| Bar Width | Result |
|---|---|
| 28-30 mm | Bee space may be too large; bees may bridge with small comb between bars |
| 32-35 mm | Optimal for standard temperate worker comb |
| 36-38 mm | Slightly tight; bees may propolize bars together more aggressively |
| 40+ mm | For drone comb sections or honey supers where larger comb is desired |
Bar Thickness
The bar itself (the depth of the wooden piece) affects the hive. Standard thickness is 18-25 mm. Thicker bars are sturdier when lifting heavy comb, less likely to warp, and provide slightly better insulation of the brood nest from above. Thinner bars use less material and create a slightly larger interior space.
Minimum practical thickness: 18 mm. Below this, bars may flex under the weight of a full honey comb, which can weigh 1-2 kg.
Comb Guides
Without any guidance, bees sometimes build comb at an angle to the bar, or attach comb to multiple bars creating cross-comb. Comb guides on the underside of the bar solve this problem.
The guide provides a surface that encourages bees to start comb in the desired orientation — hanging straight down from the center of the bar.
Guide Types
Type 1: Triangular ridge The classic top bar hive guide. The underside of the bar is beveled to a sharp ridge running lengthwise. Bees attach their first comb to this ridge and build downward symmetrically.
Construction: Using a hand plane, cut a 45° bevel along each long edge of the bar’s underside, meeting at a central ridge. Or cut a simple V-groove down the center of the bar underside.
Type 2: Foundation strip A narrow strip (5-10 mm wide) of old wax comb or commercial wax foundation glued to the center underside of the bar. Bees recognize wax immediately and begin building from it.
In the absence of commercial foundation, melt and pour a thin strip of beeswax into a groove or along the bar center. Allow to solidify. This works as well as commercial foundation strips for guiding comb.
Type 3: Wooden lath A 5-8 mm thick strip of thin wood nailed to the underside of the bar, running its full length and centered. Bees attach comb to the lath edges and build downward.
Type 4: Notch/groove A 3 mm wide × 5 mm deep groove cut along the bar center, filled with melted wax. Provides both a wax starter and a mechanical guide.
Guide Placement
The guide must run along the exact center of the bar’s underside. If the guide is off-center, comb will grow off-center and may contact the adjacent bar. Check guide position before installation by measuring from both bar edges to the guide center.
Frame Spacing in Framed Hives
For Langstroth-style framed hives, bee space applies differently. The frame itself has specific dimensions, and the spacing between frames (and between frames and hive walls) must maintain bee space.
Frame Spacing Standards
Most commercial frames are designed for 35 mm center-to-center spacing (matching natural worker comb pitch). This is maintained by:
Hoffmann self-spacing frames: The top bar of each frame has widened shoulders that contact adjacent frames, automatically maintaining 35 mm spacing. No additional spacers needed. The standard choice for most beekeeping.
Castellated spacers: Metal strips with precisely punched slots, one per frame. Installed at the top of the hive box. Each frame hangs from a slot. Available in 33, 35, and 42 mm spacings.
Wooden runners: Strips of wood with regular notches cut at 35 mm intervals. Frames hang in the notches. Simple to make by hand.
Loose frames: No spacer system. Beekeeper manually spaces frames by hand at each inspection. Least consistent but requires no additional parts.
Bee Space at Walls
In addition to between-frame spacing, the gap between the outermost frame and the hive wall must be maintained at bee space (6-9 mm). If this gap is too large, bees build burr comb between frame and wall. If too small, they propolize the frame to the wall.
In a Langstroth hive:
- Standard box interior width is 465 mm
- Ten standard frames at 35 mm spacing occupy 350 mm
- Remaining 115 mm split between two ends = 57.5 mm per side? No — this is wrong.
Correct calculation for a 10-frame Langstroth:
- Interior box width: 465 mm
- 10 frames × 35 mm spacing (center to center) = 9 spaces × 35 mm = 315 mm + half frame width on each end
- Frame top bar width (Hoffmann): 38 mm
- 10 frames × 38 mm = 380 mm…
The actual geometry: 10 frames in a 465 mm box. Each frame top bar is 35 mm wide in the body (Hoffmann shoulders extend to 38 mm). Bee space (6-9 mm) on each end, between the end frames and the box walls.
Critical check: After assembling any new hive, verify end bee space by sliding frames to one end and measuring the gap at the other end. Adjust box width or frame count accordingly.
Measuring Bee Space in Practice
Tools: A simple bee space gauge is more useful than any calculation. Cut a piece of wood or metal to exactly 6 mm wide and 9 mm wide (or make a step gauge combining both). Use these to check all gaps in your hive before placing bees.
Quick field check: A bee space gap is approximately the width of a small pencil (6 mm) to the width of a standard pencil (9 mm). Workers pass through such gaps but cannot build straight comb there. You should be able to slide a pencil (not a pen) through any bee space gap with slight resistance.
Spacing for Different Comb Uses
One bar spacing does not fit all purposes. Some beekeepers use different spacings in different hive sections:
| Spacing (center-to-center) | Use |
|---|---|
| 32-35 mm | Worker brood comb |
| 38-40 mm | Mixed worker/honey comb |
| 42-45 mm | Honey-only comb (bees build thicker honey combs) |
| 38 mm | Drone comb (slightly wider cells) |
In a top bar hive, standard practice is to use uniform 35 mm spacing throughout. In a Langstroth hive with supers for honey extraction, some beekeepers use wider spacing in honey supers (8 frames at 42 mm spacing instead of 10 at 35 mm) to encourage bees to build thicker honey combs that extract more cleanly.
Summary: Key Numbers
| Measurement | Value | Notes |
|---|---|---|
| Bee space | 6-9 mm | Maintained everywhere between components |
| Worker comb pitch | 35 mm | Center-to-center comb spacing |
| Standard top bar width | 32-35 mm | For temperate-race worker comb |
| Drone comb pitch | 40-42 mm | Larger cells, thicker comb |
| Top bar thickness | 18-25 mm | Structural, thicker = sturdier |
| Frame-to-wall gap | 6-9 mm | Each end of frame row |
| Entrance height | 8-10 mm | Allows bees, excludes mice |
These numbers are the dimensional grammar of beekeeping. Once internalized, you can design any hive configuration — from a simple log with starter comb guides to a stacked Langstroth system — with confidence that your bees will cooperate with your management rather than work against it.