Question about solid oak pillars...

[james000222]

I have cut some 7"x7"x5' pieces of white oak that I just cut from some oak saw logs. I plan to use as pillars to support a small pavilion. They will be on top of a 3' concrete pillar base (surrounded by stone). These pieces of oak are still about 200 lbs each - beginning to crack a bit - I'm working linseed oil into them and will seal with polyurethane.

My question: does that sound OK? never done this before...

 

[buzz sawyer]

Would be nice to see a drawing of the project. Do the pieces have the center (pith) in them yet? That would make them more prone to cracking but it is a great outdoor wood. Shrinkage is mostly radial and tangential but I don't believe it shrinks much lengthwise as it dries.

 

[james000222]

Sure, and thanks. Here's what I've done so far. There is an existing concrete patio. I marked out the location for the concrete bases, drilled 5x holes for rebar, inserted rebar (adhesive too). Wired at two places going up. Built a form for the 7"x7"x3' concrete pillar, bolted it (temporarily) to patio - poured concrete. capped it with a top w holes to get the rebar tops in exactly the right spots I needed. Removed form, bolted the 3' concrete pillar to the patio with 3" angles and concrete bolts. These will be surrounded by stone - see picture - and capped with granite at the junction with the oak pillars.

The oak was cut in Oct about 9 months ago - laying up on wood supports, with ends painted. Cut the first beam on my sawmill about a month ago, cut the second one last week. They started cracking pretty fast even after linseed oil. that seems to have slowed it some, but still some.

My plan is to drill 5 holes in the base of the oak pillars, cut the rebar down to 3", and mount the oak pillars on the rebar, then bolt to the concrete pillar top on all four sides. The rest of the pavillion will go up after that of course.

 

[buzz sawyer]

I'm no expert but I think you'll be fine. The oak will continue to crack to some degree but I don't see it as a problem. Almost every large beam construction I see has a lot of cracking.

 

[Oldengr]

I know your question was about the oak but I would have some concern about the concrete patio. How thick is it? If it is a standard patio about 4 inches thick you are putting a petty substantial load on it. There should be some type of footings under the pillars. Maybe you have already considered this and did not mention because you only asked about the oak. I think you have real nice looking plan and I'm only trying to ensure you are considering all aspects.

 

[james000222]

Thank's for that - it is worth considering, and my plan has changed over time. Ground is thick, very hard-packed clay under 4-inch, 3000psi concrete with rebar mesh. I do not have footers (floating pad). Based on total estimated weights - the pavilion will be a max of 4000 lbs spread out over the 4 pillars - which are 7"x7". Each pillar has about 1000 lbs of stone on the base - but thats spread over 21"x21".

 

[ironman_gq]

That's 2000lbs per pillar base which should be OK considering my 10k vehicle lift only requires a 5" slab for rated capacity (5k per post 12x12 base plate)

 

[Oldengr]

I will make my last comment on footings. My initial comment is based on experience from years with Army engineer units then residential construction and finally a city building inspector. I've worked on and have seen various structures similar to yours and they have all had footings or pile and grade beam foundations. I have not worked in your state and do not know what the building codes say. It is my opinion that there should be footings. That being said it is your structure on your property and you are the man on the ground. From your posts you have put a lot of thought and effort into planning and construction and if you are comfortable with your plan go for it. I believe you will have great looking structure when complete and hope you will post some pictures.