Load Rating for 6x6 lumber support columns?

[CCCBuilder]

I'd like to find some tables for load ratings for 4x4 and more specifically 6x6 support columns that cover species/grade/length? Whether they do the math or not is okay, such as at 10' tall this many kips or just simply to show the lumber's compression ratings parallel to grain and how this changes with height (length) of the column?

Around here Treated SYP is most common but been really fed up with how much it twists and bows, so starting to consider using Douglas Fir "#1 or better" 6x6 posts. From what I have found, at 8' high we are looking at load rating of 20-25 kips depending on bow? Wouldn't mind someone confirming or a least showing any handy source for tables/charts to refer to when verifying if the lumber is capable for the load.

 

[jerseyshore]

If you're designing for a deck, I think treated SP is most common in majority (all?) of the US. I'm sure the prescriptive IRC tables have allowable post values if this is for a residence.

I agree about the twists and bows, I have 3 of them on my front porch that I curse myself out for not realizing until the framer put them up.

For high loads and or taller columns I just use PSL (or treated PSL) columns. The Trus Joist catalog has load tables for these columns.

 

[WARose]

The 'Timber Construction Manual' 'Wood Engineering and Construction Handbook' (at least the version I have: 3rd ed. by Faherty & Williamson) has column tables. But you have to go into the table with the adjustment factors already applied. (I.e. for modulus of elasticity and F'c if I recall correctly.)

Those tables don't account for bowing however. Back when I did timber design, I use to have general notes that specifically prohibited using members where there was bowing. (Including moisture content requirements.)

 

[dold]

Check the back pages of Simpson wood connector catalogs. IIRC there are quite a few tables for posts (and studpacks) of different sizes.

 

[CCCBuilder]

Jerseyshore, we've installed some of those in the past. They may install nice and plumb/straight but come back 6-12 months later and it's abysmal. Trying to get away from any treated 4x4 and 6x6 when doing decks. Doug fir seems to claim to be resistant to elements, wondering how long. Cedar is a good alternative but do not believe Cedar is good for high loads. For a deck and no hot tub I think it might work.

This is specifically more for residential basements. Sometimes steel columns are not in the plans or if it's a remodel situation it's much easier to tie timber together and hints the doug fir 6x6 scenario.

I will check the Simpson catalog. Do not have the handbook you speak of WARose but I will check that too. Overall I was hoping for some online resources to link to and save/print PDFs off for quick reference later.

 

[jerseyshore]

I wouldn't take the risk of using untreated wood for decks exposed to elements.

For indoor residential, I very rarely specify a solid 4x or 6x post. 99% of the time it's built-up 2x4 or 2x6 columns. Much easier.

Like I said when the loads are higher I use solid PSL posts. I've never had a problem with those bowing or twisting after time.

Are lally columns that hard to get in your area? That's another easy alternative since they sell them at most hardware stores and they're simple to install.

 

[CCCBuilder]

Do you have a quick reference/guide for built up 2x4 and 2x6 columns? I've considered that but just always assumed it was much less strong than the timbers. General framing lumber around here doesn't really have any elasticity ratings, we're lucky if we are even told what species it is (most isn't marked).

Will check into PSL posts for sure, they would be a special order item is the only drawback.

For the lally columns, most of them say something like 'temporary post or permanent secondary' on them if we're talking about the same thing? The kind that have several slots for two bolts and one end has a screw jack setup? Here's an HD link to what we have available in our hardware stores locally. Notice they don't really say anything in the details about it not being a permanent primary column but the fine print packaging does. A true steel cylinder post that is cut/welded to size isn't something they keep on the shelves.

 

[jerseyshore]

True lally columns are thin walled steel columns with concrete in the middle. Nearly everyone has them in their basements in the northeast US. They are still pretty easy to get.

The screw jacks are usually used for temporary purposes, although they become permanent because people just leave them in place. I think Tiger brand has a procedure that can make it a permanent installation and permitted by code. Rarely done though.

Usually any lumberyard these days has engineered lumber in stock including posts. Maybe LVL posts as opposed to PSL posts, but same difference.

Here's a quick reference for built-up columns. This is based on DFL #2, most common lumber type around here.

You could always use Forte which is a free software for simple designs if you want more options.

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