What makes a good shed steel?

If you read garden shed reviews, you sometimes see comments like:

• The steel seems thin and flimsy.
• Materials supplied are weak and flimsy.

Now there can be some truth in these comments. As various shed makers use different quality and thicknesses of steel.

The steel used for garden sheds is thinner than either roofing steel or fencing steel. The strength of your garden shed is determined by its design and the way it is constructed. The thickness of the steel determines your sheds longevity to corrosion. Corrosion is the enemy to longevity, if steel has anti-corrosion treatments (like additives and galvanization), the resulting steel is strong but will also endure harsh environmental conditions.

Material science has advanced significantly since the days of the old, corrugated iron shed. Today’s steel is much stronger and easier to work due to its chemical composition.

At Sheds4less we use steel that is 0.32 bmt as we believe that this gives the best cost/performance ratio.

What to look for when researching steel for your garden shed?

There are two main criteria to review.

• The thickness of the steel.
• The quality of the steel.

Some shed makers can be less than forthright in supplying this level of detail – not us, as we believe we have chosen the best value steel for the job.

Here are some tables to help.

How thick should steel be in garden sheds?

We use 0.32BMT sheet steel for our sheds as we believe that it gives just the right balance between strength, longevity and cost. But we do also specify the chemical composition.

Steel Thickness	Thicker				Thinner
BMT (mm)	0.41	0.32	0.30	0.25	0.20
BMT (inches)	0.0164	0.0129	0.0120	0.0097	0.0082
Guage	27	28	30	32	34
Typical Total Shed Weight (KG +/-10%)
3.0 x 3.0 Gable	150	120	110	90	76
3.0 x 2.3 Gable	131	102	96	75	47
3.0 x 1.5 Skillion	107	83	78	61	38
1.5 x 1.5 Skillion	69	54	51	40	25
Typical Warranty (years)	30+	20 - 30	10	5	2

Adding Chemical Elements to Steel for Garden Sheds

Steel used in the construction of garden sheds and other outbuildings requires specific mechanical properties to ensure adequate strength, durability, and workability. The properties of steel can be fine-tuned by adding alloying elements during the steelmaking process. When producing steel for products like garden sheds, common alloying elements include carbon, phosphorus, sulphur, aluminium, silicon, and manganese. Each element imparts distinct advantageous qualities.
Certain chemicals can be added to the steel at the rolling stage to alter the Tensile and the Yield strength of the steel.

• Tensile strength measures how much the steel can be stretched.
• Yield strength measures how much it takes to break the steel.

Steel used in the construction of garden sheds and other outbuildings requires specific mechanical properties to ensure adequate strength, durability, and workability. The properties of steel can be fine-tuned by adding alloying elements during the steelmaking process. When producing steel for products like garden sheds, common alloying elements include carbon, phosphorus, sulphur, aluminium, silicon, and manganese. Each element imparts distinct advantageous qualities.

Here is the "recipe" we use for our steel.

Carbon	Phosphorus	Sulphur	Aluminium	Silicon	Manganese
40	12	11	35	1	19

Adding Carbon and Manganese will increase the tensile strength while Phosphorous and Sulphur will increase the yield strength
Adding Silicone and Aluminium will increase the corrosion resistance.

For garden sheds, you want steel that handles loads like high winds well, but also resists everyday wear-and-tear. The combination of these two strengths and anti-corrosive additives in your shed’s material means it’ll be tough enough to take on various challenges thrown by nature and time while keeping its shape.

Carbon

The most widely recognized alloy addition to iron is carbon. Introducing measured amounts of carbon serves the very functional purpose of increasing steel’s hardness and tensile strength. Higher carbon content prevents denting which is important for long-term sturdiness. The enhanced strength from carbon also allows the use of thinner steel sections while upholding structural integrity. Using less material can lower production costs. However, steel with over 0.5% carbon is prone to brittleness and difficult to weld. A carbon range of 0.2-0.3% balances strength with adequate ductility and weldability for garden shed construction.

Phosphorus

Additions of phosphorus promote strength and hardness in steel through solid solution strengthening. Up to 0.4% phosphorus can dissolve in the iron matrix during heating and remain in place once cooled to room temperature. Even at these modest portions, the dissolved phosphorus obstructs dislocation movements in the crystal lattice which makes steel more rigid. Phosphorus also expands the temperature range in which austenite* exists, delaying the transition to weaker ferrite. This produces a finer-grained microstructure providing better impact toughness. These benefits permit thinner sections as mentioned for carbon. But phosphorus greater than 0.1% risks hot shortness cracking during manufacture. * a solid solution of carbon in a non-magnetic form of iron, stable at elevated temperatures. It is a constituent of some forms of steel.

Sulphur

Common levels of about 0.05% sulphur bolster steel’s machinability which is the ease of cutting and shaping with tools. Sulphur combines with manganese in steel to initiate manganese sulphide inclusions along grain boundaries. These particles act as chip breakers by preventing continuous metal shavings. Instead, machining snaps off tiny, manageable chips that prevent tool clogging. Clean machining is vital for mass-producing quality shed panels. However, too much sulphur also causes hot shortness like phosphorus. Excess sulphur can additionally produce longitudinal cracking during hot or cold mechanical working.

Aluminium

Aluminium is appended to structural and pipeline steels to control grain size through the hindrance of recrystallization and grain growth. The fine, equiaxed grains output by aluminium’s influence serve to enhance strength and toughness. Additionally, the dispersed particles resist creep deformation over time especially when sheds may handle snow loads. Aluminium’s strong reactive affinity for oxygen also allows it to collect residual oxygen molecules missed during deoxidation. This protects from detrimental effects like internal porosity and inclusion formation that undermine steel products. But concentrations beyond 0.10% risk problems from incompletely dissolved aluminium during production which necessitates close control of additions.

Silicon

Most steel contains 0.5-1.0% silicon which elevates strength moderately and improves acid corrosion resistance due to silicate formation. Paint adhesion receives a boost from silicon since its oxides generate reactive sites for coating chemical attachment. Silicon slightly assists scale removal during hot rolling which smooths the finish. When utilized as a primary shed building material or for fasteners and fixtures, these attributes furnish satisfactory longevity and aesthetics. However, silicon content must stay below 5% as overly high silicon steel becomes extremely brittle.

Manganese

Serving multiplicative mechanical and processing functions, manganese routinely composes over 1% of finished steel. It foremost escalates hardenability allowing quenching and tempering processes for heightened strength. The colossal affinity of manganese for combining with oxygen outweighs every other element. This virtually eliminates oxygen imperfections during steel production. Manganese also teams with sulphur to establish the tiny sulphide inclusions that ease machinability. Lastly, manganese restrains the adverse effects of minor residual sulphur, phosphorus, oxygen, and nitrogen by preferentially binding them first. The importance of manganese cannot be overstated for its indispensable steel enhancement effects. Still, steel plants must control levels below ~1.8% to prevent uncontrolled carbide and nitride development.

Checking the quality of steel for garden sheds.

We use a 5-stage test program for our incoming steel to ensure it meets our specifications.

• Pencil Hardness Test - The pencil hardness test is the simplest form of hardness test. Pencils are pushed into the sample and the coating hardness is identified by the trace generated.


• Salt Spray Test The salt spray test measures the corrosion resistance of coatings and materials. During salt spray testing, an accelerated corrosive attack is produced to predict how well the coating protects the metal.


• Crosscut & Pull-off Tests. - The cross-cut test is a method of determining the resistance of paints and coatings to separation from substrates.


• The Erichsen Cupping Test - The Erichsen deep-drawing test is used to determine the stretch-forming capacity of sheet metals.


• Impact Test Impact - Testing of metals is performed to determine the impact resistance or toughness of steel by calculating the amount of energy absorbed during fracture.

If you pick a shed made from steel with high tensile strength and proper treatment against corrosion, you'll have yourself a sturdy structure that stands up well against the elements.

Find the Shed to Fit Your Space

With over 3,000 different garden sheds you are bound to find a shed that fits your space. Use our online shed selector to find the right size and right door configuration to suit your needs.

Click here for our shed selector tool.