I've decided to use a 4x6 in (nominal) pressure treated beam resting on 4x6 in adjustable post bases ( http://www.homedepot.com/p/Sim...ase-ABA46Z/100375175 ), bolted to sonotube poured concrete pillars. The problem is, the beam needs to be 23 ft in length, and I don't know if 24 ft beams in 4x6 actually exist. If they don't, what are my options ? The actual width of the beam needs to be 3-1/2 inch to fit in the galvanized post base.

Any advice appreciated. Arc ?

Only option I can think of would be to "sister" 2x6's if that would be acceptable from a structural standpoint.

Powers idea is great. Maybe even use a 2 by 8 if you need more load bearing for that span.

2 x 6 x 24 feet are $19.27 at Lowes.

quote:

Originally posted by 41:
Powers idea is great. Maybe even use a 2 by 8 if you need more load bearing for that span.

2 x 6 x 24 feet are $19.27 at Lowes.

Not knowing the span between support posts, it would be difficult to say what beams would be right.

Having said that, I strongly suspect that if I were doing that deck I would be using at least 2x10s.

quote:

Originally posted by wrightd:
I've decided to use a 4x6 in (nominal) pressure treated beam resting on 4x6 in adjustable post bases ( http://www.homedepot.com/p/Sim...ase-ABA46Z/100375175 ), bolted to sonotube poured concrete pillars. The problem is, the beam needs to be 23 ft in length, and I don't know if 24 ft beams in 4x6 actually exist. If they don't, what are my options ? The actual width of the beam needs to be 3-1/2 inch to fit in the galvanized post base.

Any advice appreciated. Arc ?

What is your span? I would just splice together 2x's, depth dependent on span. You can find nailing patterns on the web.

Really you shouldn't need a 4" wide beam though.

The problem with doubling 2x6 or 2x8 boards is that the result is only 3 in thick, but it needs to be 3-1/2 in thick, which is the actual thickness of a 4x6 or 4x8 nominal.

I've seen something about sandwiching plywood between the boards, but I don't know what nominal thickness of plywood is 1/2 actual, to make up the difference for a total of of 3-1/2, or what type of plywood would be proper. Is there pressure treated plywood using the same chemicals used in the pressure treated lumber ?

Span is another question, which may depend on the type and size of the resulting beam.

quote:

Originally posted by was0311:

quote:

Originally posted by wrightd:
I've decided to use a 4x6 in (nominal) pressure treated beam resting on 4x6 in adjustable post bases ( http://www.homedepot.com/p/Sim...ase-ABA46Z/100375175 ), bolted to sonotube poured concrete pillars. The problem is, the beam needs to be 23 ft in length, and I don't know if 24 ft beams in 4x6 actually exist. If they don't, what are my options ? The actual width of the beam needs to be 3-1/2 inch to fit in the galvanized post base.

Any advice appreciated. Arc ?

What is your span? I would just splice together 2x's, depth dependent on span. You can find nailing patterns on the web.

Really you shouldn't need a 4" wide beam though.

The beam wouldn't be 4", it would be 3.5 actual, which is 4x nominal. I haven't figured out span yet, until I can figure out how to make a beam that's 3.5 inch thick, to fit the 4x6 in galvy base plates.

quote:

Originally posted by wrightd:
The problem with doubling 2x6 or 2x8 boards is that the result is only 3 in thick, but it needs to be 3-1/2 in thick, which is the actual thickness of a 4x6 or 4x8 nominal.

I've seen something about sandwiching plywood between the boards, but I don't know what nominal thickness of plywood is 1/2 actual, to make up the difference for a total of of 3-1/2, or what type of plywood would be proper. Is there pressure treated plywood using the same chemicals used in the pressure treated lumber ?

Span is another question, which may depend on the type and size of the resulting beam.

A couple of pertinent comments from a structural engineer:

Anytime you get over about 15' in span length with a timber beam you're looking for trouble. A 23' span is too long for sawn lumber, especially for a member holding up a floor. You need intermediate supports if you're going to use sawn lumber. If you want to stick with wood at that span length, then consider going to a glulam beam (expensive!).

Even if you insert an intermediate support at mid-span, reducing your span from 23' to 11'-6", a six-inch deep sawn lumber beam won't have enough strength to carry the load. You need to go to a deeper beam.

Unlike S4S sawn lumber, there is no difference between the actual thickness and the nominal thickness of plywood. To get the 3-1/2" beam width you're looking for you need to insert a strip of 1/2" plywood between the two outer pieces of 2x lumber. This is what is done for lintels over doorways and windows, for example, to get a width that matches the rest of the stud wall width. You won't be counting on the plywood to provide any structural (flexural) strength, it's just a spacer, so it need not be continuous over the length of the beam.

Thanks,

Sap

In pricing a beer keg ramp, I called a saw mill 60 miles west. Far in the country. The lumber price was less than half and they cut it on the spot to exactly what you want.

Five 3 x 6 x 12' full were $94 tax included. The mill charges by the board foot. This is for red oak.

Do you have a truck that can haul a 24' board?

quote:

Originally posted by wrightd:
The problem with doubling 2x6 or 2x8 boards is that the result is only 3 in thick, but it needs to be 3-1/2 in thick, which is the actual thickness of a 4x6 or 4x8 nominal.

I've seen something about sandwiching plywood between the boards, but I don't know what nominal thickness of plywood is 1/2 actual, to make up the difference for a total of of 3-1/2, or what type of plywood would be proper. Is there pressure treated plywood using the same chemicals used in the pressure treated lumber ?

Span is another question, which may depend on the type and size of the resulting beam.

You could use PT plywood in between joist, it won't weather as well as the joists if installed vertically. Is there a reason you want such a wide beam? You should be able to find narrower ties to you sonotubes (great idea btw) without more expense.

Edit: Just read your original post. You could use those supports, just add blocking so they are tied to either side. Really, you should be able to find joist supports to embed to the sonos.

Sister 2x boards. I built a deck with several beams that size using sistered 2x8s carriage bolted to notched 6x6 posts that were set on concrete with brackets. The posts were located at the ends of each beam and under each splice. The deck was only 2.5 feet off the ground but it was very sturdy.

quote:

Originally posted by SapperSteel:

quote:

Originally posted by wrightd:
The problem with doubling 2x6 or 2x8 boards is that the result is only 3 in thick, but it needs to be 3-1/2 in thick, which is the actual thickness of a 4x6 or 4x8 nominal.

I've seen something about sandwiching plywood between the boards, but I don't know what nominal thickness of plywood is 1/2 actual, to make up the difference for a total of of 3-1/2, or what type of plywood would be proper. Is there pressure treated plywood using the same chemicals used in the pressure treated lumber ?

Span is another question, which may depend on the type and size of the resulting beam.

A couple of pertinent comments from a structural engineer:

Anytime you get over about 15' in span length with a timber beam you're looking for trouble. A 23' span is too long for sawn lumber, especially for a member holding up a floor. You need intermediate supports if you're going to use sawn lumber. If you want to stick with wood at that span length, then consider going to a glulam beam (expensive!).

Even if you insert an intermediate support at mid-span, reducing your span from 23' to 11'-6", a six-inch deep sawn lumber beam won't have enough strength to carry the load. You need to go to a deeper beam.

Unlike S4S sawn lumber, there is no difference between the actual thickness and the nominal thickness of plywood. To get the 3-1/2" beam width you're looking for you need to insert a strip of 1/2" plywood between the two outer pieces of 2x lumber. This is what is done for lintels over doorways and windows, for example, to get a width that matches the rest of the stud wall width. You won't be counting on the plywood to provide any structural (flexural) strength, it's just a spacer, so it need not be continuous over the length of the beam.

This exactly. Guy knows his stuff. Engineered lumber is way stronger than sawn lumber (in the longer lengths). You will save yourself a ton of grief

quote:

Originally posted by SapperSteel:

quote:

Originally posted by wrightd:
The problem with doubling 2x6 or 2x8 boards is that the result is only 3 in thick, but it needs to be 3-1/2 in thick, which is the actual thickness of a 4x6 or 4x8 nominal.

I've seen something about sandwiching plywood between the boards, but I don't know what nominal thickness of plywood is 1/2 actual, to make up the difference for a total of of 3-1/2, or what type of plywood would be proper. Is there pressure treated plywood using the same chemicals used in the pressure treated lumber ?

Span is another question, which may depend on the type and size of the resulting beam.

A couple of pertinent comments from a structural engineer:

Anytime you get over about 15' in span length with a timber beam you're looking for trouble. A 23' span is too long for sawn lumber, especially for a member holding up a floor. You need intermediate supports if you're going to use sawn lumber. If you want to stick with wood at that span length, then consider going to a glulam beam (expensive!).

Even if you insert an intermediate support at mid-span, reducing your span from 23' to 11'-6", a six-inch deep sawn lumber beam won't have enough strength to carry the load. You need to go to a deeper beam.

Unlike S4S sawn lumber, there is no difference between the actual thickness and the nominal thickness of plywood. To get the 3-1/2" beam width you're looking for you need to insert a strip of 1/2" plywood between the two outer pieces of 2x lumber. This is what is done for lintels over doorways and windows, for example, to get a width that matches the rest of the stud wall width. You won't be counting on the plywood to provide any structural (flexural) strength, it's just a spacer, so it need not be continuous over the length of the beam.

A listen closely to structural engineers. To answer your points:

The beam will be 23 feet long, but I will be putting in pier supports at any frequency required, whatever is appropriate. I never intended using a beam that long only supported at the ends, I didn't communicate that clearly.

Regarding your comment about a beam depth, I have flexibility. The deeper the beam, the lower height my sonotube cement piers, because I won't be using any posts between the galvy shoe and the beam itself, because this section of the deck is very close to the ground. If you can suggest a depth of beam and spacing of pier supports, that would solve the hardest part of replacing this improperly built deck I inherited. The load will be normal 40 psf for decks, on 8 foot joists, with the ends anchored to a 2x whatever header board attached to the house, and some length of overhanging on the beam on the other side. The deck that it is replacing it is 8 feet deep by 23 feet in length long-wise along the house. Very simple, but this is the crutch of the whole problem for me. So I basically need a recommendation for beam depth and distance between each pier support underneath. The existing old deck it is replacing was completely improperly built in almost any way you could imagine. It was so bad, I even knew it was a problem, and I'm not an engineer nor carpenter by any stretch. But I'm handy and enjoy the work. I'm not committed to 40 psf, I'm glad to overbuild rather than underbuild, that's the way I approach everything in life anyway. It pays off in software, so I'm sure it pays off in carpentry up to a point.

Regarding your statement about the plywood not providing flexural strength, that is good to know, I had no idea that was the case. I didn't know that nominal = actual in plywood, so that answers that question. But if I did build a beam with 1/2 plywood in the center, would ext grade work with the pressure treated lumber ? Or would that plywood not be moisture and insect resistant equivalent of the lumber sides ? Or could I paint the plywood with copper preservative, then seal the edges, etc. ?

Do you really have a 23' unsupported span? If so 4x6 is WAY undersized.
If you have a 23' span supported by multiple footings, you have many options.
Sistered 2x lumber with 1/2 plywood sandwiched makes the correct thickness..

Is this new pressure treated wood compatible with galvanized steel fittings? Seems to me I read that it wasn't.

Guess I better check. I'd imagine it would be, but I'll call Simpson Strongtie and ask.

quote:

Originally posted by wrightd:
. . .Any advice appreciated. Arc ?

You've been using the term "beam". I think what you really mean is "joist". But maybe not. What rests on the top surface of your "beam"? Is it your deck boards (in which case we're really talking about joists), or is it the bottom of joists that cross it at a 90 degree angle (in which case it really is a beam)? Or, are you using saddles to hang your joists off the side of your beam?

Word "pictures" are hard to convey. A sketch would be really useful.

To give you any useful advice on member sizes for your deck, I need to know:

-- What is the spacing of your joists center-to-center?

-- What dimension lumber are you using for your deck?

-- What kind of lumber, ie: what species of wood? For example: white pine, Idaho pine, oak, or something else? The different species have significantly different maximum flexural and compressive and shear stress values.

-- What loads do you plan to put on your deck?

-- How do you plan to fasten all the members together?

Probably no help but...

I built a large Gazebo (18 x 20 roof) and anchored it down. It was built to be moveable if so desired, think like a mini barn built on runners, but I used 3 6x6 beams for runners.

I just set 1/2 inch anchor bolts in the concrete piers, then drilled through the beam and using a coupling nut bolted through the beam with a bolt, actually used threaded rods cut to length.

But if your beam is only 3 inches thick you might not want to drill through it. If using three 2x6" or 8" (4.5 inches thick) and it would be fine.

A quick and dirty sketch...

For a 23' span use 4 posts/footings. If you go 7' apart (on center) the footings/posts on the outside edges will be 1' inside the outer edge of the deck.

Then build your 23' beam out of 2 - 2"x8"x24', with 1/2" plywood between (to make up for your 3 1/2" post bases).

Easy-peasy

You may want to look at the CPTZ concealed post tie from simpson strong tie. Basically, it is a knife-blade post anchor that can go in between 2 ganged 2X's and provide a bolt-through connection. It takes 2 anchors into the piers and has a 1" standoff plate (code) so the beam isn't directly in contact with the concrete.

Ken