Shelving Units
Shelving Racks or Shelving Units are multitiered shelving structures, usually free standing. These can be very efficient storage options, but safety is a common issue.
Types
There are 4 main types of shelving rack used by diyers:
Heavy duty angle iron shelving units, eg Dexion
- industrial duty
- industrial looks
- industrial price tag
- bracing recommended
Low cost angle iron steel shelving
- medium duty
- need bracing and stabilising to be safe
Wooden shelving units, usually home made
- can be made any shape or size
- can be made any strength
- can be economical
Moulded plastic shelving units
- extremely quick & easy assembly
- medium duty
Quick assembly metal shelves
- Not popular for DIY use
- slot together quickly & easily
Woven Bamboo
- too light for loads heavier than laundry.
Heavy duty angle iron units
These consist of holed angle iron uprights with sheet metal shelves, and angle iron or wood bracing. The big daddy of shelving units, industrial duty, industrial looks and industrial prices. The only practical option for heavy storage.
Dexion is the best known brand, and heavy duty angle iron shelving is often called Dexion, regardless of brand.
Usually grey painted, but very old units are often dark green.
Units are mostly sold as 3' wide bays in a choice of depths and height. 12" 18" and 24" are common depths, with other sizes also seen.
There are a number of different brands and hole patterns, and different systems don't generally fit together well. Bodge togethers are often possible, but not ideal, with shelves often being not exactly horizontal and not as well supported.
1" M6 roofing bolts are the usual choice for assembly.
A shelf should be fitted at ground level to create a rigid box structure for the legs, and to spread the load on the floor.
Uprights can be cut with an angle grinder.
Lightweight angle iron
A low cost version of dexion, these light steel shelving systems are available from high street stores & DIY sheds. Strong enough for household storage if stabilised and braced, but too often these units are used with neither, and in such condition aren't entirely safe.
More than one kit can be used to make a taller unit with more shelves, or to make units twice the depth.
A shelf should be fitted at ground level. Omitting this leaves the legs able to bend and topple. If that leaves you a shelf short, a light wooden frame can replace the bottom shelf.
Quick assembly metal shelves
Often used industrially, but not often seen in DIY use. The industrial units are pricey. These assemble in minutes.
Wooden shelving racks
An alternative to dexion & lightweight angle iron shelving is wooden shelving racks. The big advantage of these is flexibility, they can be whatever size and shape you like. They therefore fit every space perfectly, unlike metal shelving.
Appearance is much softer than metal units. If desired, uprights and shelf edges can be rounded, and bracing made decorative.
They may be finished with varnish or wax for indoor use. Paint is better avoided as scratching is likely.
2"x2" uprights give a lean shelf rack system suitable for typical household loads if well braced and well jointed. Well jointed means metal reinforced joints (small London brackets or large corner braces), with a minimum of 2 screws into the upright and 1 into the shelf. 2x4 gives a tougher system.
Free units may be made from assorted scrap for storage sheds, basements etc. Non-flush doors are no good as shelves, the uneven surface is impractical.
Timber shelf units can be made adjustable by sitting the shelves on blocks fixed to the uprights.
Plastic shelving racks
Moulded plastic shelving units have a big advantage: great ease and speed of assembly. They're also imperviousness to damp.
Designs vary, so check your unit for stability. If not fully stable, it will need fixing to a wall or other rigid support.
One limitation with plastic shelving units is they're not readily modifiable to create larger assemblies or custom layouts.
Bamboo & Willow
Shelving units of bamboo and similar materials, often with woven fibre shelves, are only suitable for very lightweight uses, such as laundry storage.
Breeze Blocks
Occasionally breeze blocks are stacked to make supports for wood shelves. If designed and built well this can make strong units, but without sufficient means to resist sideways forces, such units can be unexpectedly unstable, and unsafe.
Timber shelves
Shelf Materials
A full discussion of the different sheet wood products is found in Sheet Materials. A summary follows.
Chipboard
12mm chipboard is adequate for most household loads, but tend to sag in time. 18mm is better for larger units and heavy loads. Chipboard should sit on a supporting rail on all 4 sides, and additional front to back supports are recommended. Chipboard has little water resistance.
Plywood
Ply is much tougher than chip. WBP ply is water resistant.
OSB
OSB is a cheaper alternative to ply with similar characteristics.
Timber
Real wood shelves look good indoors, and are stronger than chipboard. Pineboard looks better than planks and is easy to use.
Melamine
Melamine or formica is laminated chipboard. Wipes clean and better looking than chip, but just as weak, and the edges and corners tend to break up in time.
Cutting shelves
There are 2 ways to arrange shelves.
_ ___________ _ |_| |_| | | |_ _| |_|___________|_|
One is to make cutouts at each corner of each shelf to accept the uprights. Its quicker to make a template from paper or cardboard and use this to cut the shelves, but check the template fits all positions first, often it won't.
_ ___________ _ |_| |_| | | _| |_ |_|___________|_|
The other way is to not use cutouts, in which case the uprights must stand beside the shelf sheets.
Adjustable wooden units
Timber is used to make a full self supporting frame. This rectangular frame has 12 lengths, 4 uprights, 4 top strips and 4 bottom strips.
Small wood or metal supports are fixed to the frame, and wooden shelves can then be placed in any of the preset positions. Supports every 8" give plenty of choice as to where to put shelves, and shelf positions can be changed any time. Shelf supports can be heavy duty metal corner braces, or wood blocks cut from frame timber offcuts.
A point to watch when fitting support pieces is that if the supports are too large, or the vertical spacing between them too small, shelves will fail to clear the supports above when lifted. If this happens, its impossible to get shelves in or out. This dictates the spacing and size of the support pieces.
Shelf supports
There are 5 options to support the wooden shelves
Framework
horizontal timbers run round under the 4 edges of the shelves. This is the strongest option, and enables use of relatively weak shelf materials. Additional crosspieces make the shelves even tougher if necessary.
Blocks
Small wooden blocks can be attached to the uprghts for the shelves to sit on. This creates near point loads, so weak shelf materials such as chip and MDF should be avoided.
Brackets
Little metal brackets may be used, one at each corner. For weak shelf materials like chip, use a pair of medium brackets to give good support.
Slots
The last option is shallow slots in the uprights, into which the shelves slide. An extra inch or so thickness should be used for the uprights due to the slots. The main advantage is that close slot spacing can be used, the restriction posed by using support blocks is gone. However it is more work, and any cutting mistake is hard to correct. To prevent the shelves being pushed out, the rear slots can either be covered on the back or cut to less than full depth, with the shelves cut to match.
Library thingies
Slotted metal strip runs up each side. A small metal tab is placed in position to sit each shelf on.
Bracing
Strips of timber running across 3 sides at an angle work fine.
With timber shelving, very small amounts of joint movement are acceptable, since movement does not undo the fixings, and this makes it also possible to use small London brackets in corners for stiffening.
Safety
Safety problems are common with shelving units. Metal shelving is especially prone to this. When assembled as usual, these units are often a hazard, and their lack of bracing makes use illegal in an industrial environment (unless some means of restraint is added).
Most racks are supplied without adequate bracing, and a child (or adult) crashing into one could cause it to fold over sideways, crushing anyone underneath it or caught between its shelves. Due to the lever effect the forces involed in such collapses are often sufficient to break bones or kill. Metal shelving systems are the worst in this respect. Once the units bend a small amount, the loads on the shelving act to tend to cause complete folding, even when the initial force has been removed. This is a well recognised issue in industry.
Stability
Tall shelves that aren't stable against toppling and not next to a wall can use a strip of wood attached at the top that runs horizontally to another shelving unit or a wall. Racks fixed remotely must be well braced to achieve a completely stiff system to avoid bolts coming undone.
Wood
Wooden shelving should be fixed to a wall or braced.
Metal
Metal systems are different to wood, as any joint movement at all progressively undoes the bolts, causing units to become precarious. Metal systems therefore require sufficient bracing to prevent any joint movement at all.
Heavyweight units can achieve this with bracing on 3 sides, or fixing to a wall, or fixing multiple units together to share any side loads.
Light metal systems also need bracing on 3 sides, but are typically too shallow to be safely untopplable on their own. They need fixing to a wall or to other shelving units to make a larger rigid structure.
Brace details
All shelving racks not fixed to a wall need bracing on 3 sides to be safe. 2 braces are not enough. With for example left and rear bracing, the right side can still move a little and the unit twist, and this small movement causes joints to come undone.
Small triangles of metal in corners help lightweight shelves resist crumpling at the corners, and stiffen the units to some degree. They are not effective for bracing, and don't prevent bolts coming undone over time.
Bracing consists of a strip of wood or metal at 30 to 60 degrees attached across each of the 3 sides. The triangle shapes thus formed give the unit rigidity in all directions of movement.
Torque
Doing up metal unit fixing bolts with pliers doesn't give adequate rigidity. Use a socket or spanner to obtain sufficient torque.
Maintenance
Bolts loosen in metal shelving racks, even when braced and stabilised. They just loosen much more slowly, such that an all round tightening is only needed every 1-2 years. If overlooked, the racks gradually become weak, unstable and unsafe.
Racks without sufficient bracing (on 3 sides) can loosen quickly. In the worst case I once saw an unbraced rack loosen to the point of collapse in a couple of days.