6×6 pressure treated
Emily Wong
Updated on June 15, 2026
The load capacity of a 3-foot #2 grade 4×4 is 17,426 pounds, and a similar 6×6 is 20,834 pounds or 16% better. However, an 8-foot 4×4 supports 6468-pounds and 2339-pounds at 14-feet, while a 6×6 is 18032 and 10550-pounds respectively – or 64% and 78% more load capacity.
How much weight can a 6×6 hold up?
A 6×6 with 12′ span can support 2000 lbs. if you assume a conservative 1400psi bending stress. If you do a good job bonding the two members together, your double 6×6 can support more than 4,000 lbs.
Can I use a 6×6 as a beam?
The distance a 6×6 can span as a beam depends on the species of wood, grade, grain orientation, moisture content or seasoning, condition, and load. Southern Pine (SP) 6x6s will span 5” to 8” further than other common softwood species of the same grade.
How far apart can 6×6 posts be?
The maximum spacing of 4×4 deck posts should be 6 feet on center, while the maximum spacing of 6×6 deck posts should be 8 feet on center.
How strong is a 6×6?
If you assume a conservative 1400psi allowable bending stress, a single 6×6 with 12′ span can support about 2000 lbs. So your double 6×6 can support at least 4000 lbs (possibly more if you do a good job bonding the two members together so that there’s no slip between the faces).
How tall can a 6×6 post be?
Six-by-Six Posts
A 10-foot-tall six-by-six Douglas fir or southern pine post can support an area of 256 square feet under a load of 50 pounds per square foot, which is more than seven times as much as a comparable four-by-four post.
Should you use 4×4 or 6×6 deck posts?
While there may be a handful of circumstances that only require the minimum 4×4 deck post, you will more than likely want to choose a 6×6 post for the deck. It provides more stability for larger decks, the ability to hold a heavier load, and more room for notching.
How much does an 8 ft 6×6 weigh?
They are solid and heavy about 95 pounds.
Can a 6×6 be used horizontally?
Almost absolutely. A 5′ span is small enough that there’s almost no shed you could build that wouldn’t be fine on those timbers.
Is 6×6 better than 4×4?
6×6 or 4×6 will also give you less traction in specific conditions, than a 4×4. In snow/ice and other low traction situations, you have way less traction. And the exact reason I run a SINGLE rear wheel (not dually) rear on my pickup. Winter traction is FAR better with all the weight on 4 wheels instead of 6.
Why are my 6×6 posts splitting?
While extreme loading can cause a wood beam to split and would indicate a sign of impending disastrous collapse, usually the splits or cracks found in wooden posts and beams are due to shrinkage as wood dries, occur along the grain, and do not raise a structural concern.
Can a 6X6 span 10 feet?
To answer you question, no a 6X6 will not carry that span, even if you have only a roof to support. The strength is in the height of the beam, not so much for the width.
What size beam do I need for an 18 foot span?
Thus, for a 18 foot span, you will need atleast 3-2×16 or 6×16 size of wood beam. For a 18-foot spans, the wood beam has to be at least 16 inches in depth and 6″ in width (3-2×16) used for residential building, wood frame structure or projects.
