Are 2 2x4s as Strong as a 4×4? (The Truth Revealed!)

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Are 2 2x4s as Strong as a 4×4?

During woodworking projects around your house, on your deck or in the garage you may be faced with the dilemma of choosing between 2 2X4 studs joined together or a single 4X4 stud. Are 2 2x4s as Strong as a 4×4?

All parameters being the same, 2 2X4s are not as strong as a 4X4 under vertical load. 

The actual cross sectional area of 2 2X4s is 10 ½ square inches (3”X3 ½”), while that of a 4X4 is 12 ¼ square inches (3 ½”X3 ½”) or almost 17% higher. But there are other factors that come into play too!

Are 2, 2X4s as strong as a 4X4?

Quite often a 4X4 is milled from the center of the tree trunk which tends to be weaker than the sections away from the center from which 2X4 is milled. So the benefit of a higher cross sectional area may get negated.

The wood grains in a 4X4 will run in one direction but the wood grains in two 2X4s could run in opposite directions. This could make 2 2X4s as strong as a 4X4.

The method of joining the 2 2X4s will also play a role in how strong the bond between the two pieces is and how effective they are in functioning as a single unit. 

The best way would be to apply a wood adhesive before nailing them together. This will ensure that any load is evenly distributed across the entire joint.

Failure by Buckling

Studs fail by buckling under the vertical load. The failure, as expected, will be on the thinner edge. So, the cross sectional dimension is more important than the cross sectional area

The “capacity of wood” is defined as the constant load at which the stud will buckle and fail. This can be calculated using the “capacity of wood column calculator” by Jonathan Ochshorn.

The table below gives capacity (lbs) for SPF (spruce-pine-fir) studs at different unbraced heights:

UNBRACED HEIGHT (FEET)2, 2X4sCAPACITY (lbs)4X4CAPACITY (lbs)TIMES STRONGER
2’9,61318,9921.97
4’7,32315,9512.17
6’4,30910,6142.46
8’2,6026,6782.57
10’1,7114,4522.60
12’1,2043,1522.62
14’8912,3412.63
16’6851,8042.63

The question, “Are 2, 2X4s as strong as 4X4?” is not very material for a workbench, table, bed, etc. as the height will be in the 2′ to 4′ range. As you can see from the above table the loading capacity is extremely high and you have nothing to worry about.

GMS Intro
GMS Intro

How Much Weight Can 2 2×4 Hold Vertically?

2 2X4s SPF (spruce-pine-fir) column with unbraced height of 8 feet will be able to hold a compressive load of 2,602 pounds before it buckles.

The load 2, 2X4s can hold depends, primarily, on the wood species and the unbraced height. The table below gives you a range, based on the “capacity of wood column calculator” by Jonathan Ochshorn.

WOOD SPECIES6’8’10’12’
Douglas Fir – Larch5,3723,2562,1431,509
Hem – Fir4,5572,7471,8051,270
Spruce – Pine – Fir (SPF)4,3092,6021,7111,204
Southern Pine5,1543,1182,0511,444
Note: Figs are in lbs

Which Is Stronger 2 2×4 or 1 2×6?

2 2X4s are stronger than 1 2X6. The thinner edge of 2 2X4 is 3” while the thinner edge of 1 2X6 is only 1 ½”. As a result 2 2X4s will not buckle under much higher vertical loads.

If both, 2X4 and 2X6 are single studs then, of course 2X6 is stronger than a 2X4. The thinner edge in both cases is 1 ½” but the thicker edge for 2X6 is 5 ½” while that of 2X4 is 3 ½”.

The Table below is for SPF (spruce-pine-fir) obtained from the “capacity of wood column calculator” by Jonathan Ochshorn, as mentioned earlier.

Unbraced HeightVertical Load Capacity2, 2X4s (lbs)Vertical Load Capacity1, 2X6 (lbs)
6’4,3091,574
8’2,609897
10’1,711577
12’1,204402

However, if they are used as a beam or joist then 1 2X6 will be stronger than 2, 2X4s. This is because the edge taking the buckling load in the case of 1 2X6 is 5 ½” while the edge taking the buckling load in the case of 2 2X4s is 3 ½”.

Thank you very much for reading the post. I do hope you found it informative and useful.

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