Cedar vs. pressure-treated pine for pergola posts

SteveinMD

I searched for the answer to this question on the forum but didn't find what I was looking for so here goes. I am getting ready to construct a pergola roughly according to these plans:

http://www.popularmechanics.com/home...ergola/3352816

They suggest a western red cedar structure with the exception of the posts which are to be pressure-treated pine 4x4s wrapped with cedar 1x4s. Their design has the posts sitting in anchors slightly above grade. In my case the posts will be sitting slightly below the grade of my patio which has pavers i.e. concrete footings were poured with CBSQ anchors so that the lower edge of the posts will be around 1.0 inch below the top edge of the pavers which themselves rest on stone dust and should drain quickly. So in terms of moisture it's not as ideal as having the posts sitting above grade but probably better than having the posts embedded several feet down in the footers.

Anyway, my question is whether it is better in terms of longevity of the structure to use pressure-treated pine 4x4s or use cedar 4x4s. I've read differing opinions about which lasts longer. Generally pt-pine is supposed to be prone to movement as it ages so this would be a disadvantage though some say it lasts longer. Thanks.

sdsester

I used to design and build exterior structures like pergolas, decks, trellises, benches and things. One material I used a lot was round lodgepole pine. It is very dense (for a soft conifer) and stuff treated decades ago still looks nice (I did not use pressure treated wood). You can find lodgepole pine with 100 or more years of ring growth in a tree perfectly straight, 4" in diamater (when bark is peeled) and 100 or more feet tall. They grow so close together and burn so hot they are loved/hated by foresters.

Redwood was the dimensional outdoor material of choice in California and cedar has similar, natural, insect resistant qualities. The grain of both was a bit tighter than pine which kept it from checking with damp weather quite so much. Properly cared for I think redwood and cedar looked better longer. I had any ends of cedar and redwood going into the ground thoroughly soak treated.

Fact is any soft grain would like pine, redwood, cedar look terrible if you do not keep them up with regular maintenance.

I also put lots of teaks and other hardwoods into landscape environments. I raced a 35' sailboat with a teak deck that was never oiled or touched in any way but to clean spills from things. By nature, things like teaks, kapur and other hardwoods held up better but of course were outrageous when you compare front end costs. Quite practical if you factor in maintenance.

Of course the deck of the sloop never came in contact with soil. Just lots of sun and salt water. California what it is, the boat got regular pest control inspections for things like termites.

You are on the right track. I would pour your footing to code and with sanitubes or whatever. Attach your timber above ground. Just plan annual maintenance into whatever you choose.

Nailbags

stay with the Pressure treated it will out last the cedar.

SteveinMD

Thanks for your suggestions. Since the exposed wood will be cedar no matter what what do you suggest I treat it with to keep it looking decent and last longer?

juryduty

I agree go with Cedar or better yet, Redwood. They just last, look and smell better. PT stuff looks ugly and might contain chemicals like arsenic.

Gecko

I built a 10x12 Pergola out of pressure treat using 6x6 posts 9'H and they will last a long time. Suggest putting the posts on a deck plate if bulding onto a PT deck and using zinc screws/lag bolts. I build mine from scratch off a plan found on the internet for $504 in 15 hrs with a full custom design (meaning no premeasured or marked wood). If you searh some companies they actually give you a material list and full instruction manual. Didn't take me too long to figure out I could save thousands by purchasing the material (okay did the math to calculate the lumber) and building it myself...........In fact, the same Pergola was at Costco for $2650 on sale not too long ago.

ruffsawn

in my opinion cedar is the ideal wood for outside use. most pt wood I see rarely has any penetration of treatment to the heartwood, so it rots from the inside out. Also the treatment used now is not as effective as the older treatment though somewhat less toxic. Cedar heartwood is very rot and pest resistant. Here in michigan there are very old cedar posts on farms still in fair condition. But black locust is the best, followed by white oak then sassafras. I use cedar for fence posts, sill plates, deck wood, planters. I use pine as well for posts, i just burn the sapwood off the end like the old timers.

YerDugliness

I'd recommend the cedar or redwood, too, for aesthetic reasons as well as b/c of my experience with PT...here it is:

We went to HD and told them we wanted to build a pergola using 4X4 PT posts as well as 2X6 PT stringers. We told them we wanted to paint it to match the trim work on the back wall. We were told to use Kilz II primer and regular latex housepaint.

We proceeded to paint the lumber before cutting. We must have spent a week getting multiple coats of Kilz-II and good quality latex exterior house paint on the boards....only to have the surface coatings BOTH bubble up and peel off the PT lumber, leaving ugly areas where the wood was visible.

We complained to HD about this and were told that the government was requiring different methods of PT to eliminate the arsenic from the process, and that was resulting in PT lumber that would not hold paint.

Well, we had told the HD representatives about our plans to paint before construction and had followed their advice. We filed a complaint with the HD corporation regarding the issue and they sent a local HD representative out to see our problem areas. He told us that the PT lumber needs a considerable length of time to dry out before it is painted or the problems we faced would be ongoing. We were not told this in the store when we bought the materials, in fact the representative in the paint department assured us that Kilz-II would stick to the "new" PT lumber.

If you are going to clad all your PT lumber with cedar or redwood, well, that's not going to be a problem for you, but if you plan on using any PT lumber that will be exposed, be sure you let it age for 6 months or greater so that the moisture will not cause the paint bubbling I mentioned.

In the end, we're about 80% through. This is the "before" photo:



Here's how it looks now:



I still need to trim out the feet of the posts to hide the brackets, and we plan to add solar screen fabric in the 22" wide spaces between the horizontal stringers.

Building codes are pretty tought here in Huntsville, TX...we built the pergola under a permit and received raves from the inspector for the work. Recently we were visited by the Central Appraisal District to investigate the "addition", but when we showed the appraisal district representative that the pergola can be removed quite easily and is not affixed to the main structure of the home, we were told that the valuation/taxes on the house would not be affected as the structure is "portable". We have to wait for the next tax statement to make sure they honored that, but have high hopes for now.

Cheers!

Dugly

SteveinMD

Thanks for the additional comments on this thread. Dugly your pergola looks great! I will be covering (wrapping) the PT posts with cedar and am not painting the structure. All of the exposed wood will be cedar. I will probably be sealing it to help it last longer. If you have any advice about that please let me know. Surprisingly when I contacted our city government about whether I would need to pull a permit to build it or adhere to any specific codes they said 'no' to both questions since it is not attached to the house and is nowhere near the property line.

Gecko

Here is the one I built for $500 and 15 hrs of my time - all from scratch. Not bad for a chic!

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SteveinMD

Hah! I think I've already spent 15 hours thinking about the project and and it hasn't even really started yet!

YerDugliness

If you are going to use PT posts, try to select some that are lightweight. When we bought the PT from HD, we selected the straightest we could find and noticed that some of them were heavier than others. I'm guessing those were wet from the PT process. As the pergola has aged we have noticed that a couple of the 4X4 posts have developed a curve (and one actually twisted), and a few of the horizontal stringers have warped, too. You might want to give your PT 4X4's some drying time before you start....although the cedar clading might well provide enough support that it would keep the PT 4X4's from twisting.

As for sealing the cedar, that's sorta tricky. Cedar is an "oily" wood and doesn't accept varnish well. If it were me, I'd consider trying a deck sealer such as Thompson's Water Seal. That will penetrate the cedar and provide some protection from the weather, but you'll need to replenish it every year or two to keep the cedar looking new. It is easily sprayed with a tank-type pump sprayer.

If it weren't cedar, I'd have recommended marine "spar" varnish b/c it doesn't yellow as it ages.

Cheers!

Dugly

ews2001

Hey, do you mind sending me the free plan that you found online?...Your pergola is amazing, I'd like to do something very similar.

Gecko

The plans were not free, I found them on the link below and did the calculations for purchasing the lumber myslef by looking at the material sheet and doing simple math. I made my own template for the scallop ends and measured everything out ..........basically once the corner posts were in and the 4 cross pieces I build the ladders on the deck and then just lifted them up. Only one of the four ladders was out a bit and didn't fit, and took a sawzal and cut it into place.........just make sure you are square and measure the distances evenly. If you buy this (also available at Costco) then you pay someone to mark all the spots and cut the wood pieces for you.........if you are a bit handy, then you can build it........download the material sheet and the installation sheet and have fun........

http://www.outdoorlivingtoday.com/ol...php?pid=BZ1012

The only help I had was fitting the last ladder into place up top since it
was out a bit, and I'm 5'3" so I'm sure you can do it...any questions email me at fastlane169@sympatico.ca


Shawna

ews2001

This is fantastic, thanks Shawna, I'm definitely a DIY guy and will look for places in my area where I can take a plan like this and have the hardware list made up for me. I'm excited to get a start on it...thanks again!