How to set post for deck

Reply

  #1  
Old 07-26-10, 06:05 AM
Member
Thread Starter
Join Date: Jun 2008
Location: Virginia
Posts: 150
Received 0 Votes on 0 Posts
Question How to set post for deck

What is the proper way to set a post in concrete when building a deck?

Should I put gravel in the hole, post on top, and then put concrete around the post, or does concrete need to be under the post?

I am planning to bury the post somewhat and not use footings.
 
Sponsored Links
  #2  
Old 07-26-10, 09:10 AM
Join Date: Mar 2005
Location: USA
Posts: 6,130
Received 0 Votes on 0 Posts
How high is the deck and if it higher, do you plan to use the area under it for a patio, etc.?

Is it ledger supported or a true free standing (preferred) deck?

For long life, the classic way is to pour a Sontube (a round, waxed cardboard form for concrete) at each post location and insert a Simpson bracket into the fresh concrete to provide sliding lateral strength and separate the wood from the concrete and moisture. The post is installed a day or two later.

Dick
 
  #3  
Old 07-26-10, 09:22 AM
Member
Thread Starter
Join Date: Jun 2008
Location: Virginia
Posts: 150
Received 0 Votes on 0 Posts
Originally Posted by Concretemasonry View Post
How high is the deck and if it higher, do you plan to use the area under it for a patio, etc.?

Is it ledger supported or a true free standing (preferred) deck?
It's not very high off of the ground - around 4 ft at most. It is attached to another deck that is ledger supported.
 
  #4  
Old 07-26-10, 10:24 AM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,933
Received 54 Votes on 47 Posts
IMO and many locations do not allow putting the post in the concrete. This is do to the concrete adsorbing moisture and holding it next to the wood post accelerating rot. The post should also be kept 1" off the concrete with a pad/bracket that Concretemasonry mentioned.
 
  #5  
Old 07-26-10, 10:44 AM
Join Date: Dec 2005
Location: USA
Posts: 3,188
Received 0 Votes on 0 Posts
I agree that setting the post on a concrete footer is the preferable method, but the right kind of PT posts will withstand rot if they are buried. At least that is true for posts treated with CCA. I don't know if that is true for ACQ. I have a deck built in 1983 and it is supported by four 6X6 posts in 4' deep holes and surrounded by concrete.

Most of the PT stuff you can buy is ACQ treated and not suited for ground contact, however, the last time I checked you can still buy CCA treated posts and timbers that are treated for burial/ground contact. If you decide to use buried PT make sure you get material suited for the purpose.

It's probably easier and cheaper to rent an auger and pour some footers.
 
  #6  
Old 07-26-10, 08:05 PM
Member
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
Received 0 Votes on 0 Posts
Wayne, CCA treated doesn't exist anymore. SOME ACQ's are rated for earth contact, but burying wood in the ground just isn't a good idea, even if it is so rated.

Pour footings, set a post or column base in the top of the footing that will hold the wood an inch above it the concrete, and attach your posts to that base.

Having a ledger is going to create other issues -- properly flashing it being the biggest. Also, how old is the house? If it was in '77 or before, you are going to be dealing with lead paint, and the EPA has come out with a new set of rules in that regard. (Contractors beware -- you have to be certified in order to touch it!!)
 
  #7  
Old 07-27-10, 03:54 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,967
Received 2 Votes on 2 Posts
Mike, I note my new liability policy has a lead paint abatement exclusion on it. You have to purchase a specific policy rider to cover it, and I am sure you will have to produce certification in order to get it.
 
  #8  
Old 07-27-10, 06:08 AM
Join Date: Dec 2005
Location: USA
Posts: 3,188
Received 0 Votes on 0 Posts
Originally Posted by lefty View Post
Wayne, CCA treated doesn't exist anymore. SOME ACQ's are rated for earth contact, but burying wood in the ground just isn't a good idea, even if it is so rated.

Pour footings, set a post or column base in the top of the footing that will hold the wood an inch above it the concrete, and attach your posts to that base.

Having a ledger is going to create other issues -- properly flashing it being the biggest. Also, how old is the house? If it was in '77 or before, you are going to be dealing with lead paint, and the EPA has come out with a new set of rules in that regard. (Contractors beware -- you have to be certified in order to touch it!!)
CCA treated products are still available. I think their use is restricted in residential application, but I don't know for sure if it is prohibited. One of the providers I found on line recommends either CCA or ACQ for ground contact or submerged applications so it may be that ACQ is also effective in preventing rot.

The point I was trying to make in my original response was that there are PT products that will not rot in the ground or in contact with concrete. They are treated at much higher levels than the PT products carried at big box stores.
 
  #9  
Old 07-27-10, 06:11 AM
Member
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
Received 0 Votes on 0 Posts
Yes Larry, a contractor will have to purchase a rider in order to be covered. I'm sure that the co. will want proof of certification before they'll write the coverage. The EPA has extended the deadline for obtaining the certification until late this year. Get certified, because you don't want to get caught working illegally.

As far as a homeowner doing their own work on an older house, I'm not sure how that will be handled.

At this point there is more confusion than there are clear answers. The square footage involved in a project is a perfect example. When attaching a ledger to a wall, one source says it's the sq. ftg. of the ledger. Another says it's the sq. ftg. of the entire wall! And anything more than 20 sq. ft. (exterior)comes under the law. Interior, it's anything more than 6 sq. ft.
 
  #10  
Old 07-29-10, 06:19 PM
Member
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
Received 0 Votes on 0 Posts
Wayne,

I just googled "EPA CCA", and after 12-31-03, The manufacture and use of CCA PT lumber for residential applications is prohibited, unless an exception is granted. (If somebody wants an "exception", they better have VERY deep pockets!!)

Forget the CCA -- it's just going to be worth the cost to obtain an 'exception'.

As far as burying wood in the ground, that's just not a good idea. Wood, treated or not, is GOING to rot when it's in contact with dirt at some point. Concrete in contact with dirt won't rot, at least not in our lifetime. Wood exposed to moisture is going to rot at some point, albeit 20 or 30 years down the road. If you bury the posts in the ground, they will be someplace between difficult and impossible to replace. If they are set in a base or column base, replacement is going to be pretty simple, WITHOUT destroying the rest of the deck to get it done.
 
  #11  
Old 07-29-10, 06:39 PM
Member
Thread Starter
Join Date: Jun 2008
Location: Virginia
Posts: 150
Received 0 Votes on 0 Posts
How do you prevent the metal brackets that hold the post in place from rusting? Even galvanized eventually rusts.
 
  #12  
Old 07-29-10, 06:58 PM
Join Date: Mar 2005
Location: USA
Posts: 6,130
Received 0 Votes on 0 Posts
Proper metal connectors with a space under for moisture will last longer than wood post in concrete or any soil. There are also different coating treatment for metal that have a proven history.

The history on any present wood treatment is very short because of the frequent "new" processes for preservatives since the search continues.

Dick
 
  #13  
Old 07-29-10, 07:29 PM
Member
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
Received 0 Votes on 0 Posts
adam09,

You're right -- even galvanized metal EVENTUALLY rusts. But a post or colmn base isn't going to rust to the point of being "unservicable" for probably 40 or 50 years, or more. Wood, buried in dirt, isn't going to last more than about 20. And wood decks -- I haven't torn down more than a very few that were over 25 or 30 years old. The bases will outlast the wood.
 
  #14  
Old 07-30-10, 11:01 AM
Join Date: Dec 2005
Location: USA
Posts: 3,188
Received 0 Votes on 0 Posts
Originally Posted by lefty View Post
adam09,

You're right -- even galvanized metal EVENTUALLY rusts. But a post or colmn base isn't going to rust to the point of being "unservicable" for probably 40 or 50 years, or more. Wood, buried in dirt, isn't going to last more than about 20. And wood decks -- I haven't torn down more than a very few that were over 25 or 30 years old. The bases will outlast the wood.
I guess we'll have to disagree on this. I have a deck, built when my house was built in 1983. It is supported by 6 PT posts set in concrete. The last foot or so st the top is set in dirt. I know this becasue when I redid my deck I planned on replacing the posts. I dug down to the concrete to find zero rot. I have a retaining wall that I built 25 years ago from pressure treated timbers rated for burial/ground contact. Last year I replaced foundation plantings and I dug down to a buried deadman to check it out. There was no rot. I have 200' of split rail fence with posts buried 2' deep. The fence is also 25 years old. The posts are not PT, I believe they are locust. I haven't checked them for rot but the fence is still standing. I replaced several rotted rails over the years but not a single post. I share a dock on a lake with several neighbors. The dock has a dozen or so PT pilings driven into the mud. I don't know how old it is but it wasa pretty weatherbeaten when we bought there 15 years ago - no rot yet.

I also have a couple of raised flower beds made from PT "landscape" timbers that I bought at a big box about 20+ years ago. They are all rotted.

The point being that not all PT wood, or wood in general, is the same.
 
  #15  
Old 07-31-10, 09:30 AM
Member
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
Received 0 Votes on 0 Posts
Wayne,

When you built your deck in '83, you used CCA treated lumber. (There was no such thing as ACQ back then.) Now, the treated that's available for residential use is ACQ. CCA isn't.

My experience with ACQ is that, even though the tag says it's approved for earth contact, it simply doesn't stand up as well to earth contact as well as the old CCA did.

We're really not disagreeing, we are simply talking about 2 different products. For better or worse, the CCA is no longer approved for residential applications (available or not). What is approved and available is ACQ, and THAT just doesn't do well with earth contact.
 
  #16  
Old 07-31-10, 10:00 AM
Join Date: Dec 2005
Location: USA
Posts: 3,188
Received 0 Votes on 0 Posts
Actually I was responding to a couple of blanket comments that CCA "doesn't exist anymore" and "wood in contact with earth isn't going to last more than 20."

Both of those statements are simply not true. I grew up on a farm that had a split rail fence that was built by my great grandfather. That fence is still standing and it's probably 80 years old. I think the posts are cedar.

Different areas of the country have different weather, wood species, soil makeup, insects and microbes. All of which contribute to rot.

Whether it's CCA or ACQ is less relevant than the treatment. A wood post (you can still buy CCA treated posts by the way) trreated at .28 PSF is not going to have the same rot resistance as a post treated at .60 or .80 PSF. MY understanding (from nothing other than surfing the web) is that ACQ treated at the same level as CCA will have a similar life expectancy.

I still believe that a post on a footer is the better method. I don't know if posts on footers are required by building code but from what I'm reading properly treated ACQ will survive just fine in a concrete filled hole.
 
  #17  
Old 08-02-10, 08:24 PM
Member
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
Received 0 Votes on 0 Posts
Wayne,

You are talking about things that simply don't exist anymore.

What your grandpa used was probably OLD GROWTH cedar. That, and old growth redwood -- certainly they would last 50 to 100 years (possibly more!) with earth-to-wood contact. The problem is that OLD GROWTH (anything) simply can't be harvested anymore. Virtually every stick of wood that you get at a lumber yard today came off of a tree farm someplace, and well over 90% of it is less than 50 years old. The tree huggers simply won't let the lumber companies harvest old growth any more.

40 years ago, when I was working a lumber mill, there were only a very few mills in the pacific northwest that could handle a log over 36" in diameter. Today, there aren't any!!
 
  #18  
Old 08-05-10, 07:54 PM
Member
Join Date: Mar 2009
Location: WA
Posts: 1,167
Received 0 Votes on 0 Posts
CCA is still being used, but I doubt it’s approved for residential decks anywhere: ProWood CCA at Universal Forest Products Hit the “more”- button

“Decks and porches present a particularly severe exposure for both the wood and finishes. Most wood members are in a horizontal or flat position. These horizontal surfaces, especially in decks, are often exposed to the direct rays of the sun and tend to collect moisture, so the weathering process is greatly accelerated. As repeated cycles of wetting and drying occur, checks tend to enlarge rapidly into cracks and, along with the end-grain surfaces, begin to retain moisture. The conditions for decay and insect attack caused by the presence of moisture are thereby greatly improved.” ------ From: Sealers and Finishes for Pressure-Treated Lumber | Southern Pine Council™ | 1-504-443-4464

Now think of a post in the ground, which used to be a tree, delivering water and nutrients from the ground to its leaves for growth and seeds. The post still has its cells aligned for optimum water delivery from the wet ground, past the concrete (water reservoir) to the air above the ground which dries it out. The remainder of the water not moved by capillary action and adhesion deposits to the bottom of the post entombed in concrete to rot because very few people treat the p.t. wood with a waterproof agent first.


Did you know? Pressure-Treated Sill Plates and the Building Code | GreenBuildingAdvisor.com

Adam09, you need a footing under the minimum 6x6 post: http://www.lancova.com/deckinfo.pdf

If using concrete, add gravel under and for backfill to drain and prevent frost heave: Building a Deck - Google Books

How Aggregates Prevent Frost Heave

Be safe, Gary
 
  #19  
Old 08-06-10, 02:49 AM
Member
Join Date: May 2010
Location: South Florida
Posts: 376
Received 0 Votes on 0 Posts
I agree w/ lefty that putting wood in-ground is not a good idea. I suspect wood life is very dependent on specific soil conditions which vary greatly based on location.

Here in S. FL where the water table is extremely shallow, a CCA wood post in-ground will not likely last more than 15 yrs., and some rot out in less than 10 yrs. If the in-ground wood posts are installed on a high sandy ridge, they’ll last much longer than those installed in-ground where ground moisture is nearly always present in varying degrees. The notion that pouring concrete around an in-ground post will prevent rot is also wrong, and they are a royal pia to remove and replace. I would be skeptical of any claims regarding life span of ACQ lumber as it has an inadequate history for in-field use to support theoretical calculations. My bet is that many homeowners have rotted posts in-ground, and don’t know they’re rotted . . . reason you read stories about decks collapsing and people being injured.

Having worked for a POCO, the giant in-ground CCA power poles can rot out in 20 yrs., and why they are subject to yearly inspection although many rotted poles are missed. Utility poles are treated at .60 lbs p.c.f. retention of CCA, a far higher level of CCA as compared to what is regularly sold at HD and Lowe’s. After the 2004 hurricanes where many power poles were broken off at base due to wood rot, as well as many laid over from being in water logged, soft ground, POCO hired a firm to come up with a better way to install power poles and extend their useful life. The method now used is to encapsulate them in expanding foam material POLE SETTING FOAM : Rainbow Tech similar to spray foam used to seal cracks. While providing a moisture barrier, it also helps stabilize poles (and pole lines) to minimize blow-down and leaning.

Marine lumber yards carry CCA and ACQ lumber Southern Pine Lumber | Composite Decking | Pressure Treated Lumber | Vinyl Sheet Piling. If for some reason I felt compelled to use in-ground posts in building a deck or fence, I would use marine grade PT lumber although I would spend the extra money to buy structural composite posts as they will likely last longer than the home. However, I see no good reason why someone would not use concrete and a post base.

Lefty is correct about CCA PT lumber being prohibited for sale to residential use applications. However, I’m not sure this is a blanket prohibition in using it on a residential property. I purchased some marine grade CCA a few yrs. ago, and was not required to sign any forms. The company delivered it to my property with no questions asked.
 
  #20  
Old 08-06-10, 05:31 AM
Member
Thread Starter
Join Date: Jun 2008
Location: Virginia
Posts: 150
Received 0 Votes on 0 Posts
Can you bury composite 4x4 posts in the ground? Would these support the weight?
 
  #21  
Old 08-06-10, 05:51 AM
Member
Join Date: May 2010
Location: South Florida
Posts: 376
Received 0 Votes on 0 Posts
Can you bury composite 4x4 posts in the ground? Would these support the weight?
It can be buried in-ground, and will support the weight as specified in tech sheets. However, this is extremely expensive material, and suggest you go w/ concrete and post base unless you’ve got money to burn. It’s especially useful in marine applications where posts/pilings are underwater . . . starting to see it used more by gov’t. around bridges as they’ve come to realize it's less costly longer run than replacing pilings fairly frequently.

TriMax Structural Plastic Lumber - Conrad Forest Products: 800-356-7146

Trimax Building Products- Trimax Structural Lumber
 
  #22  
Old 08-06-10, 03:21 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,967
Received 2 Votes on 2 Posts
Not on their own. You would need a footing to bear the weight. Not sure if they would have a moisture problem or not. Mike can advise better on that.
Scratch that, Rob already did.
 
  #23  
Old 08-06-10, 06:40 PM
Member
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
Received 0 Votes on 0 Posts
Structural plastic, yes. A composite post, no. There is a difference!!

For a deck your local bldg. dept. is going to require footings for the posts to rest on. Once you figure the cost of the structural plastic posts, you'll be extending the concrete footings above grade and install a post or column base in the top of them. That's a lot less expensive than using the longer posts.

I did bid one deck with it several years back. As I remember, the framing mat'l. (posts, beams and joists) for a 400 sq. ft. deck was going to be just under $10K. The customer went with PT framing instead.
 
  #24  
Old 08-06-10, 07:07 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,967
Received 2 Votes on 2 Posts
I have potential customers who extol the virtues of composite decking. In our area you will find mostly PT. I ask them why they want composite. They respond "it'll be there forever", to which I tell them it will be there only as long as your substructure exists. When it rots, it all comes down.
 
  #25  
Old 08-06-10, 08:42 PM
Join Date: Dec 2005
Location: USA
Posts: 3,188
Received 0 Votes on 0 Posts
Surfing around looking for some info on buried PT, I came across a UMass site that says they have PT stakes in the ground for 40 years. No rot.

Lefty - I see you live in the great NW. I lived there (poulsboro and Silverdale) for a short time on two separate occasions. You are right about there not being any old growth lumber left to be harvested. It was all cut down.

Old growth hardwoods are being harvested in the North East both NH and VT have sustainable old growth forests. At least what I think of as old growth. In actuality it is most likely second or even third growth but hardwoods seem to recover quickly. Whatever it is, the cutting is selective and actually beneficial to the forest. It is not the terrible clear cutting like I saw in Washington where entire mountains were stripped and nothing left behind but stumps, tops and erosion. I'm a long way from a tree hugger but that stuff was just ugly.

Most of New England has reforested in the last 50-60 years as less and less land is being farmed. With the exceptioon of Maine most of that is hardwood. The huge old growth pine forests that the early settlers found are long gone. They were all cut down for masts and spars and they never replenished.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description: