14 Pallet Rack and Heavy Duty Shelving Design Factors

If you are looking for racking, pallet racking, or heavy duty shelving, the design (type and style) will depend on what you will be using the storage racking for. It also depends on the depth and span of the rack shelving.

This comes into play when designing any heavy duty shelving.

A little math comes in handy for figuring out what size and type of racking or shelving is needed to handle the items stored.

In this post, we will be looking at the types of racking and industrial shelving, the sizing considerations for your shelving, and how you will be utilizing your racking or shelving.

Before we begin, we should mention that this information deals with shelving and racking not found at your local hardware store. However, many of the principles can apply to any ordinary shelving units.

With any racking or shelving project and purchase, it is important to determine all possible uses for the shelving. Again, what will you be storing? This will help you figure out what type and style is needed and the size of shelf needed.

#1 Weak points in a shelving unit.

The 4 major weak points in any shelving unit are as shown in the image above.

  • weight over the middle of the span (weakest point of the span)
  • total weight of the shelving putting stress on the vertical posts
  • shelf end attach points to the vertical posts
  • possibility of taller shelving units being top heavy and toppling over

Imagine 500 to 5000 lbs of items collapsing onto you or some other valuable asset. 500 lbs can do a lot of damage, let alone 5000 lbs. Plus the added damage to items on the racking or shelving.

#2 Shelving load capacity - what does it mean and what should you look for?

Load capacity is an important factor and is usually always mentioned as a selling point with most racking and heavy duty shelving.

Shelving Load Capacity = how much weight each shelf can handle safely without the possibility of the shelf collapsing.

Almost every manufacturer will test their shelving units to determine how much weight each component can handle and then figure out the lowest practical weight per shelf that the unit can handle, as determined by the weakest point.

Load capacities are usually figured out by the shelf span. The collapse will usually happen in the middle of the shelf span for longer width spans and not at the shelf ends where they attach to the sides.

The longer the span of the shelf means less load capacity of the shelf.

You may notice that load capacity can change with the width of the shelving. This is due to the span of each shelf. The longer the span, the less weight each shelf can handle.

Remember, racking is just high capacity shelving, so it also has shelves and this applies to racking as well.

However, load capacity ratings also take into account how much weight the shelf end attachment can handle as well.

#3 Size of the item or items - what will you be storing?

Uses for racking and shelving vary widely. It can be for small light storage (like small parts) or for large heavy storage (like drums or heavy parts).

Are you looking at storage for various size and weight items such as ?:
Small light items
Small heavy items
Large light items
Large heavy items

Will the items you are planning to store on the racking or shelving fit on the shelves? You will probably want to measure items to make sure they do fit.

Or, as mentioned, you may be trying to store something very large and heavy, drums, engines, parts, or something like an ATV, or quad, can weigh up to 1200 lbs! What kind of shelving or rack can handle that?

Mustang Material Handling
is a supplier for heavy duty shelving in addition to pallet racking and bulk racking.

Call us to price your shelving.

#4 Number of items that will be on each shelf - will your items fit?

How many items will be required for the storage space selected ? How large are the items?

Knowing both those answers can help you determine how much racking and how many shelves you need and how large each shelf needs to be.

#5 Size vs. weight of the items on each shelf - some math can be important.

Are the items you are storing dense? Small size and heavy weight? Or are the items large size and lightweight? Or somewhere in between?

This information can be important when figuring out shelving unit span or shelf width.

Are the items you are storing dense? Small size and heavy weight? Or are the items large size and lightweight? Or somewhere in between?

This information can be important when figuring out shelving unit span or shelf width.

For example, You want a shelving unit that is at least 12 feet wide, but you have very dense items to put on the shelves. At 12 ft wide, the load capacity is less than units 8 ft wide or 10 ft wide because of shelf span.

You determine that you are just under load capacity at 12 feet wide.

It may be better to get 2 units, each 6 feet wide. The much shorter 6 foot span allows for a much greater load capacity per shelf – giving you a greater margin between the actual weight and shelf load capacity.

It may be necessary to weigh items or look up weights to determine the total weight on each shelf.

When looking at shelving for smaller and lighter items, shelving depth, width and spacing become less of a concern.

Be careful when the items have a little more weight in a small package and you may be packing the shelves. The smaller weight multiplied by many items can add up quickly.

Consider if you had 100 items on a shelf that and each item weighs 20 lbs. That adds up to 2000 lbs load on the shelf – most standard shelving will not hold up to that kind of weight.

You would need shelving that has a load capacity of at least 2000 lbs. This is fairly easy for most racking, but not for heavy duty shelving.

That may seem like an exaggeration, but let’s look at a very possible scenario. You want to store 50 gallon drums weighing 400 lbs each on a shelf – 2 drums deep and 5 drums across. How much weight is that and how much load capacity do you need?

10 drums (2 x 5 ) will weigh over 4000 lbs! That is way more than most heavy duty shelving units are capable of. This will require racking and shelving to support those drums.

#6 Total weight of the item(s) you are storing - can the shelving handle the weight?

Many do not think of the vertical posts when loading or designing racking or shelving units.

Consider the example above… if you load each shelf with 2000 lbs of drums and you have 6 shelves – that makes a total weight of 12,000 lbs. Plus add the weight of the shelving itself – perhaps another 400 lbs.

Can the bottom of the vertical posts, where all the stress is, handle that kind of weight at 12,400 lbs?

Typically, the vertical supports of racking or heavy duty shelving can handle large loads. But it pays to be sure that your shelving attachment supports can handle the loads they will be supporting.

#7 Corrosive or caustic liquids stored - what if they leak?

Will you be storing things that may leak? Paint, oil, fuels, acids and solvents may cause tons of problems if they develop leaks in their containers. 

Will you be storing caustic chemicals? like acids or other corrosive chemicals? These types of chemicals that leak can cause damage to the shelving that may cause collapse. Many shelf finishes guard against caustic type chemicals, like acids, with an exterior protective coating.

Another consideration is… Do you want the shelf to contain leaks? Or do you want any leaks to easily pass through the shelf?

#8 Shelf height spacing needed for each shelf - the most overlooked factor.

This factor is overlooked more than any other when designing or building a shelving unit.

First, if you design a racking or shelving unit with 4 shelves and the unit is 12 ft. tall, what is the height between each shelf?

You might quickly think it is 12 ft. divided by 4 (12 ft. ÷ 4 = 3 ft.) – and that would be incorrect.

The correct way to calculate shelf spacing is by dividing the total height by the number of spaces. An 4 shelf racking unit has 5 spaces. So, 12 ft. ÷ 5 = 2.4 ft.  That makes a difference!

With many shelving units and racking in particular, storage goes all the way to the ceiling. In this case, spacing is determined as the number of spaces from floor to ceiling.

And then make sure the items you plan on storing can fit in this space with plenty of room above the item. Crowded items can cause all kinds of grief if you have to twist and pull to get them on and off the shelves.

With racking, don’t forget the space of the skid and spacing to maneuver with the forklift.


#9 Shelf width & span - what will fit in the space you have?

How wide a shelving unit needs to be depends on the space you have for the unit or units, and of course, how many units you will utilize.

If you have 30 feet for shelving, you won’t find shelving that spans 32 ft wide. So, should you break that space up into 3 – 10 ft wide shelving units or 4 – 8 ft wide units?

A big question is how wide will the shelves need to span? For dealing with potentially heavy loads, this is a big factor and a question that definitely needs consideration.

For heavily loaded shelves, it is probably better to go with the smaller spans and break up the shelving into as many units as practical.

#10 Shelf depth - is deeper better?

Many standard heavy duty shelving units come with narrow shelf widths, usually at 8 to 12 inches. But, the heavy duty, industrial type shelving can be found with up to 48 in depth shelf sizes.

Of course, racking can easily have deeper shelving depths. 

Bad practice is to get shelving that is not deep enough to accommodate the items stored so that items hang off the front or back edges of the shelves.

Larger heavier items should be stored on shelving that is deep enough to handle that size item.

#11 Shelving height - How high can you go? how high should you go?

Higher is usually better, but there can be some things to think about.

What equipment will you need to reach the top of the shelving unit? And if so, will you be able to handle the size and weight of the item you are storing with the equipment you have?

Also, is there a danger of the unit being top heavy and falling or toppling over? Securing the unit to the building framework in some other way may be required if this is the case. Is there something to secure to?

And… can the unit be knocked into?

Be careful of multiple units and any possible domino effect if toppled.

Remember that shelving units can weigh hundreds or thousands of pounds. The effects of falling shelving units can be devastating and dangerous.

#12 Material type of the shelving - Which is best?

Is the shelving material you want to use up to the job of spanning the width?

For example, wood shelving material is fairly strong for short spans of 3 feet or less but is lacking when compared to some steel shelving for spans up to 8 to 12 feet.

Steel can also support much more weight and loads in the vertical posts as well. Should you look for solid shelving or wire shelving? Wire shelving is strong and does the job but allows for dust or contents of leaking items above to fall onto items below..

A popular steel shelving is steel wire shelving with solid tubular steel vertical supports. This type of shelving can support considerable weight.

Racking has multiple types of shelving, but the most common is the welded wire type.

#13 Material finishes of the shelving - Is one better than another?

Will the finish of the material you choose for shelving handle the wear and tear of the items that will be going onto the shelves?

Will the finish stand up to any potential leaking contents? Like: acids or oils or solvents?

Will the finish stand up to the working environment? Will the environment be humid? Like in a humid work area or outdoors?

Most steel shelving finishes stand up to quite a bit of humidity and weather. But some, like galvanized or stainless steel, seem to handle this type of environment much better.

Some powder coated and epoxy coated finishes will stand up to most anything, even corrosive spills, and provide excellent durability in humid conditions as well.

#14 Shelf types and styles - what are the advantages of each?

Well, we have talked about many aspects of shelving, and indirectly referred to shelving material types. But, let’s go into detail about shelving types and styles.

Common materials for shelving include plastic, wood, and steel.

For strength and durability, nothing compares to steel shelving. Steel will support the most weight, support the larger spans, and have the greatest strength for shelf end attach points – the best strength for all 3 of the weak points of shelving.

Steel shelving also sometimes has the biggest cost. But, not always. Usually for the extra heavy duty, industrial shelving – it does have a higher cost.

You can utilize plastic or PVC shelving, and usually it just won’t hold up over time. Plastic shelving definitely will not work for handling larger, heavier items.

Plastic shelving is probably the weakest material type you could select for shelving.

Wood shelving is fairly strong and durable. For wood shelf end attach points, steel is usually used.

Wood shelves do have a tendency to bow in larger spans over time, but can be supported by steel


There are a lot of racking and shelving choices out there. Take your time and choose a quality unit.

Take into consideration as many aspects of how you will be using the racking or shelving, what size will fit the space you have, and the size and weight of the items you are storing.

The time and money you invest in choosing a quality  unit can be well worth it.

Expert advice doesn’t hurt either. Please let us know if you have questions about choosing your heavy duty shelving, pallet racking, bulk racking, or any racking in general.