What wood for a gazebo

[kwolfe]

I was thinking about building a gazebo for beside the pool. I was thinking about 14x18 or so which would leave enough room for dinning table and a small bar.

The question is, what type of wood would you use. I have worked a lot with pressure treated in the past, but when I get it, its always wet, heavy and tends to bow. I put in a shade sail last year using 6x6 post and they all bent a bit!

I plan on paint the entire structure. Do I have to use pressure treated for the roof and roof trusses? I can seem maybe the posts and facia board as they will get rained on, but the other would only be subject to humidity.

Just curious from others who might have built in the past.

 

[JohnT]

You want to use something that is rot resistant if it can get wet. That means cedar, redwood or treated if you go with wood.

I build posts from 2X lumber glued and nailed with ring-shank nails and then wrapped with metal or covered with a vinyl post sleeve. They go together quickly if you have a nail gun.

I had to borrow the metal brake to make the covers, but it's pretty easy when you get the hang of it.

The built-up beams seldom bend and are generally stronger than solid beams. You can add a layer of treated plywood to adjust the size to match standard lumber. For example, two 2X6s together make a 3 inch by 5.5 inch actual beam, which won't match a standard 4X6, but you can sandwich a piece of 1/2" treated plywood between the 2X6s to make a beam that measures 3.5X5.5 that matches a 4X6. With a little thought, you can make posts that cradle beams between the outer boards, making anchoring them easier.

I started doing this when I had a source of scrap lumber from a construction crew and found it works better than a larger beam.

 

[dattia]

I have a 20'X20' Gazebo in my backyard that was built by a friend of ours about 7 or 8 years ago. He used pressure treated lumber and constructed the roof with boards that overlapped each other, a modern look that was supposed to weather naturally. After a year, the boards shrank a bit and the gazebo started to leak in many places on the roof. I had him come back and put plywood and shingles up on the roof. I subsequently had the entire structure stained opaque white and put some cottage details on it to achieve the look that I had originally wanted. The roof has held up well, but I did have to replace a few of the floorboards last summer due to moisture damage from beneath. Good luck to you, I have enjoyed my gazebo immensely... it is my 'happy place'.

 

[anonapersona]

A garden show on the local radio station recently mentioned seeing a glass infused treated wood for outdoor projects that sounded like the best thing since sliced bread. He was raving about it after seeing it at a garden products show somewhere. You might try to look into that for it was said to be impervious to insects and rot. Not sure if the treatment prevented warping.

 

[pragmatic]

You want to use something that is rot resistant if it can get wet. That means cedar, redwood or treated if you go with wood.

I build posts from 2X lumber glued and nailed with ring-shank nails and then wrapped with metal or covered with a vinyl post sleeve. They go together quickly if you have a nail gun.

I had to borrow the metal brake to make the covers, but it's pretty easy when you get the hang of it.

The built-up beams seldom bend and are generally stronger than solid beams. You can add a layer of treated plywood to adjust the size to match standard lumber. For example, two 2X6s together make a 3 inch by 5.5 inch actual beam, which won't match a standard 4X6, but you can sandwich a piece of 1/2" treated plywood between the 2X6s to make a beam that measures 3.5X5.5 that matches a 4X6. With a little thought, you can make posts that cradle beams between the outer boards, making anchoring them easier.

I started doing this when I had a source of scrap lumber from a construction crew and found it works better than a larger beam.

I agree! Excellent idea! kwolfe could also wrap the manufactured beam with cedar for an all wood look.
Thanks for sharing.

 

[kwolfe]

Thanks for the laminated board idea. That sounds good.

So if the roof is all going to be under the shingles, then there should be no need to use preasure treated. Correct? It should not be subject to anything more than humidity. If I cover the columns in vinyl post covers, then they are protected as well.

Sorry, but I hate pressure treat. I know it serves a purpose, but the shrinking drives me nuts.

Redwood or cedar would be nice. Does anyone know how much more they cost? Sounds like they could be expensive.

 

[Nova13]

I'm building one now about 500 sq ft pergola style out of Cypress, 2x8's about $1.85 a ft

 

[kwolfe]

That's what I mean. The pressure treat equivalent would cost me $1.35 per ft and kiln dried white wood would run me $0.90 per ft.

I would hate to pay more for something that I am just going to paint anyway. However I don't want to build a piece of junk either.

 

[JohnT]

That's what I mean. The pressure treat equivalent would cost me $1.35 per ft and kiln dried white wood would run me $0.90 per ft.

I would hate to pay more for something that I am just going to paint anyway. However I don't want to build a piece of junk either.

Unless you like the weathered gray, you'll have to paint or stain any wood you use.

Search for "post wraps", "column wraps", "column covers" and you'll see there are some very cool, low maintenance options. This is a look I like. The stone wraps can get expensive, but they raise the wow factor by a ton when used well.

 

[msumoose]

If you would set the treated wood out for a few weeks before construction, then it would dry naturally to its Equalibrium Moisture Content. In your neck of the woods that should be somewhere around 10%. How long? Well, depends on the weather. This is the reason that installers leave hardwood flooring in a home for a couple of weeks before the install - to get the moisture content to settle to its new environment.

As for using untreated and painting, well, the paint will do about ZERO. It is a porous skim coat, and is no substitute for a treated board/beam. If there is ANY ground contact, you MUST use treated. I promise that you will be sorry if you do not. I would also use treated anywhere that will see any kind of weather. Floor joists, decking that may be along the edge of the gazebo, etc., even if it is painted. The decking under a shingled roof would be fine for non-treated or even a engineered material like plywood or OSB, as long as there is some facia to keep the water off the ends.

As for the "naturally resistant", you will find that unless you find old growth cedar (western red, thuja plicata) or sinker cyprus (taxodium distichum) it will be not much better than southern yellow pine, untreated. Whatever you do, don't use Eastern Red Cedar (juniperus virginiana) and think it will do. That would almost be as bad as putting unpainted, untreated poplar in the ground.

If you do go the treated route, lay the boards flat, and put some spacers on each row for air flow. The more uniform your pile, the straighter the wood will be.

Sometimes you can find "re-dried" treated wood - they put it back into the kiln to get most of the moisture out. Or, you can pick your own wood from the oldest packs the lumber yards have around...

 

[Nova13]

If you would set the treated wood out for a few weeks before construction, then it would dry naturally to its Equalibrium Moisture Content. In your neck of the woods that should be somewhere around 10%. How long? Well, depends on the weather. This is the reason that installers leave hardwood flooring in a home for a couple of weeks before the install - to get the moisture content to settle to its new environment.

I'm an avid wood worker hobbyist for many years. I disagree, treated wood takes many months to dry out.
The wood flooring guy are starting with wood that is already dry, 15-20%, then only adjusting that moisture content a few points stacked indoors.

You can't make that comparison IMO.

As for the "naturally resistant", you will find that unless you find old growth cedar (western red, thuja plicata) or sinker cyprus (taxodium distichum) it will be not much better than southern yellow pine, untreated. Whatever you do, don't use Eastern Red Cedar (juniperus virginiana) and think it will do. That would almost be as bad as putting unpainted, untreated poplar in the ground.

Old growth is best sure, but not avail at good price, new growth works very well in Cypress (that's what I use)



I don't like treated wood leaching its chemicals into a pool.........

 

[msumoose]

What would leach into the pool? When the wood is put into the pressure chamber the preservative is forced into the cellular structure via vessel elements and such. The preservatives used today are vastly different than creosote and, even when creosote us used today the practice is much different than even 20 years ago. By using pressure and heat the preservative is somewhat bonded within the cellulose structure. Any that isn't leaves behind its preservative within the wood as it dries, because of the lack of pressure and heat.

The "leaching" that was seen with chromated copper arsenate was seen in the arsenic element, which was surprising as the place that reported high arsenic levels in the soil was known for its high levels of arsenic in the soil anyway. You would think that the chromium would be more problematic as it is a heavy metal, but the industry was so prone to a knee jerk reaction that we cannot use CCA now, which was a far better preservative.

As for the resistant specie, numerous studies via the Forest Products Society and the US Forest Products Lab have shown that decay resistance is decreased about half in plantation grown wood There is no substitute for a wood piece of pressure treated wood, used correctly.

Also, if the wood starts out over 30% or so moisture content, it can only take days to get it to that point, and the rest of the process will take a bit longer. Either way, softwoods are only usually dried to 19% anyway, as they gain and loose water more rapidly because of density differences from their hardwood cousins. The cost to go any farther is just adding to the final cost without adding value to the consumer.

 

[Nova13]

Please take a look at this info then
http://www.builditgreen.org/attachments ... d-Wood.pdf

 

[JohnT]

Please take a look at this info then
http://www.builditgreen.org/attachments ... d-Wood.pdf

The chemicals that leach from current treated wood are both commonly added to pools as algaecides. The quantity would be low enough that I doubt it would have any discernable effect on the water. CCA is no longer used.

 

[msumoose]

What JohnT said about CCA, and...

In all cases that I have ever heard of or seen study of, there is some kind of mis-use of the wood. Burning, burying, and others come to mind that are just opposite of common sense. A study done by University of Minnesota made raised beds out of CCA treated lumber and planted vegetables in them. They tested carrots, spinach, bush beans, and buckwheat grown in raised beds built with CCA-treated wood. All the beds were at least ten years old. Soil and plant samples were taken at varying distances from the wood border. In all cases arsenic levels were highest near the wood and dropped off quickly toward the center of the beds. Example: carrots grown next to treated wood contained 4 to 11 times the arsenic found in those grown four feet away. In their worst-case scenario, the Minnesota researchers found that a 132-pound person who ate seven ounces of spinach would narrowly exceed the daily arsenic limit established by the U.S. Environmental Protection Agency. Separate tests by the Connecticut Agricultural Station reached a similar conclusion: if you ate more than 11 ounces of fresh lettuce grown next to CCA-containing boards you could exceed the limit. The actual amount of arsenic in play here is minute — just 92 micrograms in the Minnesota example — and let's face it, even for greens lovers, a half to three-quarters of a pound DAILY is some serious spinach.

For Nova13, I suggest you read up on copper. You can be poisioned just as easily by that heavy metal as well. The .pdf you listed has some innaccuracies in it. For instance, the EPA says that no amount of arsenic is OK for children, but the article says that "the ESTIMATED amount of arsenic ingested by children who play on CCA treated wood is well above the EPA limit." Well, if the limit is zero, and a child goes out into the non-sterile world, then of course the arsenic that they are exposed to is "well above the EPA limit." You can't divide by zero and then make general statements.

Azole is a pretty potent biocide, even though it is organic. Borates, as discussed on this site, has toxicity to animals and humans when ingested. Quaternary ammonium compounds can make other health effects, like mild skin and respiratory irritation all the way to severe caustic burns on skin, coma, convulsions, hypotension and death.

One can even die from dihydrogen monoxide (the carrier for all these preservatives), which is at a much higher level in the backyards of the members of this site EXCLUSIVELY.

So, saying that one is better than the other, well, depends on the use.