Simple load/span question for outdoor project?

[Jerry Olexa]

Building a simple swing set for my daughter's family...It will hold a +/- 4 ft wide wooden swing (adult type- been in family for years) but want to be sure the framework is strong enough to hold... Planning to use pressure treated lumber. I'd use 2X4 material for the 2 end triangles and make the top span of 2X6..I would reinforce joints with cross bracing in both directions...Or should I upgrade to 4X4 for triangles and 4X6 for span that holds swing.(possible overkill).Swing could be supporting as much as 600 lbs ocassionally..This is a simple project but want to be sure I am using strong enough materials to prevent later mishap..Thanks for your advice...You engineers will love this BIG :) challenge!! Thanks,

[keith ouellette]

You would be shocked at how much weight a 2x4 will support on edge. That being said it won't look nearly as nice. It will have a kinda cheap look.

For that reason alone I would use 4x4 for the base to make it look better. The thickness will add dimension it wouldn't have with a 2x4 structure.

A 2x6 top will hold plenty of weight but you also have to worry about twist which will be common in a swing bench if any actually swings in it. I would double up on the 2x6 which will prevent it from twisting and again add more dimension.


By the way. I am no engineer but I did sleep in a holiday inn last night. Wife kicked me out because I spent too much money on tools.

[Mike Nolan]

More information is needed. How long is the 2x6 and how far from the ends is the swing attached. If the swing is attached near the ends then little strength is needed.
I agree with the previous post that the nominal 2 inch dimensions is likely to be critical if anyone swings in the swing.

[Lee Schierer]

The 2 x 4 should be fine for the triangluar ends and the cross beam. The swing in the photo was made about 15 years ago for my In Laws and now resides at our house. The swing is about 5' long. We have had three adults sitting on it at once with no problems. http://home.earthlink.net/~us71na/swing.jpg As you can see the entire structure is made of 2 x 4's. By the way no one has ever accused it of looking cheap. Mostly they just want to sit and relax. It's a great place to read a book or catch a few Z's.

[Jim Matthews]

If you could find a cutoff glulam (LVL) beam designed for spanning a foundation, your load will be adequately resisted.

the A-frame design requires a substantial tie to the ground, either a concrete footer and mechanical connection or deep anchor into the ground (like a giant screw for holding tents down at a wedding reception).

You're not building for average loads, you're building for that one time when ALL the kids come over.

[Keith Westfall]

Made this for my mom before she passed away a couple of years ago. 2 x 6 construction, no sag problems.

It's made to come apart for transport, (legs fold in. top rail comes off, etc) but seemed to work OK.

188703

[keith ouellette]

Maybe "cheap" was the wrong choice of words. I still like the more substantial look of 4x4 legs and a doubled up 2x6 beam but thats just the way I see it. wish I had a picture of the one I'm thinking of but I only put new chains on it for someone. I didn't build it.

[Jerry Olexa]

Maybe "cheap" was the wrong choice of words. I still like the more substantial look of 4x4 legs and a doubled up 2x6 beam but thats just the way I see it. wish I had a picture of the one I'm thinking of but I only put new chains on it for someone. I didn't build it.

keith, the fact that you said you stayed at a Holiday Inn the night before gave your response highest credibility :)..."more substantial" is more diplomatic :)..I understand what you meant..
I just want it to look presentable for my daughter and her family and still be structually sound...Thanks for the responses, ideas and pics. I'll keep watching..

[curtis rosche]

you could always go with steel. if you go with gluelam beams you can get those for free at some places, go to a building supply place like STOCK building suply, they get the beams in long lengths like 24 ft i think and then cut them down for the buyer, then they have bunches of 8 ft or less peices that they burn or throw away cause they are too short for houses

[Richard Shaefer]

I am a structural engineer and I don't beleive overkill exists, since reserve capacity always gets used, sooner or later. You get more bang for your weight/buck going with a deeper top piece since the bending capacity of a beam varies with the square of the beam depth. i.e. a single 2x8 has roughly 4x the capacity of a 2x4, even though it's only 2x as deep and uses about the same amount of wood.

Were it mine, I'd make the A-frame ends out of 4x4's not for strength, but stability against overturning when swing goes back and forth. I'd make the top out a 4x6, minimum, and I might entertain laminated 2x8's and punch some well thought holes in them to keep the structure from looking top-heavy.

[Lee Schierer]

Were it mine, I'd make the A-frame ends out of 4x4's not for strength, but stability against overturning when swing goes back and forth.

Guys, this is a lawn swing not a regular swing set. You can't get them swinging that high!!! You can't under duck a swing that has pivots that are 8' off the ground and is 4+ feet wide. Ground anchors should not be necessary unless you live in Kansas or other tornado alley location. Also the load points on the cross beam are close to the ends of the beam not in the center. So you really get the effect of a 2 x 4 on about a 4' span not 8 foot. Note that on my design the diagonal braces to the top beam not only take out the end to end swaying, but also contribute to load support.

[Dick Thomas]

Another $.02 worth? IF you will NEVER have kids on the swing you MIGHT be OK. However, nowing how exuberant my grandkids can get with a swing, and having been a kid 60 years ago, I agree with Richard Shaefer - go with 4x4 A-frames and a 4x6 (or laminated double 2x6's) for the beam.

I'm also remembering an event from 60 years ago when too many kids got on the same type swing and caused a collapse: my younger brother was on the end with his arm underneath when it hit the groung. Consider the safety of YOUR grandkids????

[Bob Riefer]

aren't "simple" questions fun? :)

[Jerry Olexa]

I generally overkill...So the concensus seems to be 4X4's for sides and 4X6 for span...And some type of 2X diagonal cross bracing at top ...Thanks for your pics, advice...Yes Bob, simple can become complex..:)

[Kent A Bathurst]

I generally overkill...So the concensus seems to be 4X4's for sides and 4X6 for span...And some type of 2X diagonal cross bracing at top ...Thanks for your pics, advice...Yes Bob, simple can become complex..:)

SWMBO claims that one of my mottos is: "If it's worth doing, it's worth overdoing." Your plan is definitely overkill - right in my wheelhouse - tee it up.

Plus - they are grandkids, right? 'Nuff said. Plus your design might also take care of you great-grandkids.

[Brett Bobo]

+1 on Richard's position as I'm a structural engineer as well. I also agree that overturning of the frame will be the biggest concern so a shallow footing for each post would be best. Alternatively, the wider the frame, the better resistance to overturning.

[Jerry Olexa]

As a follow up, finally completed the simple swing set frame..Went with 4X4 post and 4X6 Beam..Possible overkill :)...Here tis, ready for drying and later staining...Thanks for your advice.