When trying to understand whether a 2x6 will hold a porch swing, you have to consider more than just the size of the wood. The orientation of the wood has a great affect on its strength. The species of the wood also determines how much load can be supported.
How far your 2x6 spans between supporting beams and its overall length will play into figuring its strength. The total load placed on the 2x6 has to be factored.
First, will a 2x6 hold a porch swing? Yes, a 2x6 will hold a porch swing if it meets the right conditions. The right wood, with the right span, orientation, and load will work.
If you have a 2x6 oak board and mount it straight up and down with 2x6 oak board supports every 8 inches, you should not have a problem hanging a porch swing on it.
Almost all situations you will encounter will not be as perfect as this. Many porches are made of pine. The supporting beams are 2x4's spaced 16 inches apart. Sometimes your 2x6 is laying flat. All of these conditions affect the ability of your 2x6 to support a swing.
Consider the entire load on your 2x6
When thinking about the strength of your 2x6, you have to consider all of the load that is on it. Is your 2x6 part of a support system for your roof? If it is in your porch ceiling, then it probably is support for your roof and walls.
This means the 2x6 is not only holding your swing up, but has a large load already on it.
Support your 2x6
The best thing you can do is to reinforce your 2x6 beam before hanging a porch swing. Doubling and sometimes tripling your 2x6 beam will give it the strength it needs to hold your swing.
You also need to pay attention to how much space is between your 2x6 supports. If the span between the supports is more than 16 inches, you may want to put extra supports in place.
Special cases to consider
If your 2x6 is laying flat, you will need to take extra care. A 2x6 laying flat is much weaker than one on its side. If it is laying flat, you should support it with at least 2 – 2x6's running in the same direction and bolted to it. Your porch swing should mount through the 2x6 that is laying flat and to the supporting 2x6 beams.
Check for damage
Your 2x6 and supports need to be checked for damage. If there is damage to the beams, replace them before hanging your swing.
Ask a professional
If you are unsure about your 2x6 beam and its supports, contact a professional carpenter or engineer. It is better to spend a few dollars then to have someone get hurt.
Hanging a porch swing
Once you have strengthened your 2x6 beam, you can hang your swing. To hang the swing, you will need certain hardware. You can purchase the hardware as separate pieces or in a kit.
A porch hanging kit will usually come with hangers, springs, and chains.
When measuring for your hanger placement, measure the length of the swing and add 3 inches. This will keep the chains away from the swing.
The right location
Hopefully you thought about the spot you were going to hang your porch swing before reinforcing your 2x6 beam. The ideal location will have 2 or more feet open on each side of the swing. You should leave at least 4 feet in front and back of the porch swing for the swing to not hit anything when in use.
Also, make sure your swing won't swing into another path. The last thing you want is to have your swing fly in front of someone trying to get in the door.
Do it the right way
Your 2x6 can support your porch swing. Take special care to make sure it is strong enough. Add some extra support to help it hold the weight of your swing and riders.