Help, please, wit our foundation dilemma
Morning, all!
We are working on a home remodeling project and noticed that our new foundation posts for our porch (with master bedroom built on top) will likely be in contact with soil when all is said & done. We are concerned about the structure being compromised.
The current design is up to code and the builder and his team have full faith in confidence in this format. Essentially, what they have used are 4 footings of 10″ thick concrete with #4 reinforcement bar in each direction. And, the posts are listed at “middepth.” The 6 x 6 pressure treated wood posts sit on the concrete footings (dug into 2′ x 2′ holes), and are properly mounted on the metal brackets.
At best, the builder will trim out the area around the posts, keeping some dirt off of the posts, but water (we have wet soil and a damp basement where we live) will likely be a problem.
I am wondering if anyone knows of the life expectancy of a 6×6 pressure treated wood post? We will likely be asking the builder for the posts to be shored up a bit and, if so, are collecting opinions on the best way to do this. The porch and room atop it have already been framed out so we want to make sure that any change doesn’t compromise the structure when rebuilding the footings.
Bottom line: wood in contact with soil means that failure is a matter of when not if and we would like to protect the investment of our house as much as possible.
Thanks for your help!
Replies
I'm not a big fan of ANY wood in ground contact, but there are a heck of a lot of pole buildings built that way in this country. A few years ago there was a lot of talk about pressure treated foundations (instead of concrete) even. I'm not sure anyone really knows how long wood pressure treated for ground contact will last - a long time, though.
Tipi, Tipi, Tipi!
http://www.asmallwoodworkingcompany.com
Thanks, Jim.I feel that way, too!I was surprised to learn that the current method in place is suited to county code.If you (or anyone else) can offer links to learn more about pressure treated wood and how long it can last when in contact with soil (when mounted properly on concrete, even if below grade!), I'd appreciate it!kanda
What I would do if it were mine is use something like glazing compound or plumber's putty to build a "dike" around the post, then fill the "pond" with some good, strong, melt-your-eyelashes wood preservative. (Note: Depending on the solvent used in the preservative, glazing compound may not be the best choice for the dike.)
Keep the pond full for several days, and then once a year crawl under there and refill it.
Of course, if the posts are on the sort of metal brackets that actually hold the post bottom up about a half inch from the concrete then this scheme won't work very well, but if you have those brackets then you don't have nearly as much of a problem, either.
The ACQ treated post should have a stamp that will tell or give you a ref number to check life expectancy.
You could form around the post to slightly above ground level and pour in concrete. You may want to plaster the post with black roofing tar prior to pouring concrete.
Greetings, and Welcome to BT, first off.
Ok, I'm trying to fill in the mental picture of this. The concrete foundation blocks are 10" thick and 2' x 2' square--is that just 10" down from grade, or 10" thick down some sort of hole?
With living space above, I'd be real leary of burying foundation components. Particularly burying the (likelySimpson) brackets holding the posts to the concrete footings.
All of which is moot, if the conncections are made up a ground level <g>. In that case, I'd use some sort of decorative gravel, rather than topsoil, if only for the better drainage, and better access to the connections for visual inspection if no other reason.
Thanks for weighing in, everyone!Capn Mac, thanks for the welcome!The specs I listed were those I read off of the plans. Visually, I would describe it as concrete blocks about 2' x 2' which were laid into the ground and are about 10" - 12" below grade. Atop the concrete is a bracket and fastened to the bracket is a 6 x 6 post which supports our screened porch and the room built above it.So, if I understand it, you are recommending putting gravel in around the hold to keep water and topsoil away from the posts to lengthen the life.I haven't yet been able to establish the type of P.T. wood they've used, but hope to learn more soon.I understand from our other responders that folks do generally agree that any soil in contact wood is a problem and that finding a solution which will truly keep the water & soil away from the wood and perhaps offer another layer might be best.Is that right?Does anyone know of a layman's engineering resouce or FAQ site for learning more about pressure treated wood?
Kanda,
You may have missed it, but one responder did mention wood foundations. There are people who build foundations out of PT wood, presumably with the expectation that their house will still last a long time. I don't know anything more about the practice than that, but it does imply that wood contact with the ground may not be preferable, but can be acceptable under certain circumstances.
Since you have water problems already, now, while your yard is already messed up by construction, is a good time to handle that. Get good drainage away from your home and that is probably the best thing you can do to preserve not only the posts under your porch, but the entire home. The dirt isn't what is going to deteriorate your wood, it's the water in the dirt. We have wooden structures here in the desert that have sat right on the ground for 150 years - but the soil is dry. There are a lot of people on this forum who can instruct you in proper ways to get water away from your foundation. Unfortunately, I'm just a homeowner and not one of them.
Good luck with your addition.
With a wood foundation, the wood is kept out of contact with the earth, and dry, via a plastic membrane on the outside.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
So there is a plastic membrane between the wood and the gravel footing? I thought it was just on the walls - which makes me glad that I was careful to say how little I know about the topic. It does make me wonder why they rate PT wood as approved for ground contact if they never expect it to touch the ground.
That plastic is there less to keep the PT ply dry than to keep the ground water out of the foundation/basemenmt. Aslo, the PT can handle some moisture, but it may soften the wood fibre and bend/change shape from the ground poressure.The main idea there with a wood foundation is to provide the ground water a place to go other than in the basement - just like with a regular masonry or concrete foundation. if the water is trapped in the ground next to the foundation wall it will do two =damaging things - one is find a wayu in. the other is to freeze and expand, putting exponentially more pressure on the wall than it was intended to handle. It all has to do with lateral loading, not rot.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Hey, aimless--I did notice that post, but hadn't really spent as much time digesting it... I guess I'm looking for more specifics on understanding PT wood and finding examples that have been in place for 30 years or more. But, in my neighborhood, it's all either really old construction or new construction, neither of which answers my question.I do agree about re-doing our landscape to better control for water. It's interesting, with the new roof on (even w/o gutters), I'm already noticing a difference. We had a big rain the other day and the typical water wasn't in the basement... even with the sump pump turned off. Interesting.I have a great builder who has high expectations / standards for his work. So, I know he's confident in what he is doing, but the engineers in my life differ on this and no one seems to be able to say more about the life of PT wood. One guy says we could get about 20 more years by taking a few more steps to protect the wood and design a gravel area around the post to encourage water to move away. Right now, 20 doesn't seem long enough to justify what we're putting into this renovation (or, 30, if we call his estimate conversative!).One thing for sure, I'm learning a lot about footings and foundations!K
Don't lose troo much more sleep over this, Kanda. If this PT is rated fro ground contact it will outlast you. My bigger concerns are that the fottiongs ar larger enough for the load on them, but that's another whole engineering question that we can't answer here.I live and work in Maine where we have wet clay soil, frost four feet deep, and a lot of old homes that werre built on cedar poles. I have replaced quite a numbner of them that were 80-100 years old.contrary to what has been repeated here, it is not the water that is your enemy. It is microorganisms that feed on wood. These like the presence of moisture and oxygen. The old cedar poles I have replaced were all deteriorated at around 9-12" below the ground surface- to an hourglass shape. The portion from there down the next four feet was as sound and solid as the day it was placed.Of the PT posts I have replaced them with over the past fifteen years, i have revisited several - these are continuing repeat customers - some even get yanked out for further additions and I have not seen any signs of deterioration. feel good, sleep well
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Kanda,If your builder were to bury the detail you described from your plans, the steel post bracket would be gone from corrosion long before the properly treated post was gone from rot.Assuming they use ACQ posts at a high enough retention of preservative, I'd be looking for stainless post bases. ACQ is hard on metals in close contact, very hard.Others have given lots of good pointers to you also in previous posts (no pun intended). I am curious why the designer did not specify concrete columns resting on those footer pads? It isn't terribly expensive to do, and has proven reliable.Bill
Kanda,
Just to aleviate your fears, here is a really cheap addendum to the specs that your GC may go for, especially if you sign a change order.
If you can keep air to the wood and flange, and keep water away, you can double the lifespan of the piers.
Your pier pits are 2' square and 2' deep. Cut some 15# roofers felt 2'x9' and line the pits to keep silt out of the gravel (any grade or type) that you over fill the pits with.
In addition, take some 12"x 25.5" pieces and loosely wrap the bottom of the 6x6's. 25.5" will give a circle that a 5.5"x5.5" square will fit in, if you overlap the felt 1". This will give you an even better air pocket next to the bottom of the pier and around the metal bracket.
I would not insist on the column wrap if the GC seems hesitant. I do prefer that the pit be lined and filled.
SamT
Piffin, Bill & SamT:Thanks so much for your great comments! I have learned so much and am only further in love with my favorite home building resource -- Fine Homebuilding. I'm really glad I decided to post this morning!I am still waiting to hear back from the builder on the type of PT grade which was used and how they will fill / address the hole which is still there around the current posts.I'll be checking back in case anyone else wants to weigh in!Good night to all!
K
PT house piles are common here. We just dig a hole and surround the post in concrete. Standard method is a minimum of 12" of post in the ground and 4" of concrete under it. ( this depends a lot on the soil type though )
I seem to remember that PT piles have an expected life of 90 years. Thats long enough that most people wont be around to care when they need replacing with more of the same.
Fence posts and any other timber that will be buried or in contact with dirt all have the same PT rating.
Not an exponent of the DILLIGAF system.
>> We just dig a hole and surround the post in concrete. Standard method is a minimum of 12" of post in the ground and 4" of concrete under it. ( this depends a lot on the soil type though ) << You are right, soil type is very important. Personally I would never recommend pouring concrete around a PT post unless the surrounding soil is very granular and well drained. Basically the concrete holds moisture to the post and accelerates rot. To make things worse, the post often shrinks leaving a gap between it and the concrete, in effect, possibly making the post sit in a "glass of water".
>> I seem to remember that PT piles have an expected life of 90 years. << this is strictly hearsay, but I was told a general rule of thumb is .25 treated = 25 years, .40 treated = .40 years, although personally I'd knock about 30 - 40% off of that...
See my next post for more info.
Edited 4/12/2006 7:12 pm ET by Matt
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<!---->Conditions – subject to extreme wetting and leaching and/or <!---->
<!---->where the critical use requires a higher degree of protection. <!---->
<!---->Biological hazard – very severe decay, borers and termites<!---->
Our PT stuff is mostly all CCA. In ground treatment level is H5 which according to the
folks who make this stuff....
"Exposure- outside in ground contact with or in fresh water. Conditions- subject to extreme wetting and leaching and/or where the critical use requires a higher degree of protection. Biological hazard- very severe decay,borers and termites
The marine grade H6 will likely outlast mankind
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Not an exponent of the DILLIGAF system.
One thing you should think about is you may not be able to get a termite contract with wood to ground contact.
busta
I don't think you said what area you live in...
Here is some basics on PT lumber - for the US at least ...
Right coast: PT lumber is mostly all SYP (Southern yellow pine). This wood absorbs the treating chemicals very well. There are different levels of treating available, like .25, .40 (ground contact), .60 and .80. The specific treating level should be listed on a tag affixed to the end of the lumber. the .xx means the saturation level, in PCF: pounds per cubic foot. Lumber that is .40 lasts reasonable well in the application you describe, however the soil type and how well it drains is immensely important. .60 and .80 will definitely outlast all of us.
Left coast: I don't live there, so here is what I have learned here at BT over the years: Their PT lumber is Douglas fir or something along that line and it doesn't absorb the treating chemicals very well. They "incise" the lumber - it is covered with little cuts to help it absorb the treating chemicals. Still the chemicals come no where close to fully penetrating the lumber. This type of lumber I'd be more concerned about.
You said >> And, the posts are listed at "middepth."<< Hummm I have never heard of that, although my building experience is limited to the east coast. Still I think I would have at least heard mention of the term here as I've been reading this cr@p for around 8 years.... Maybe someone else can enlighten me...
You need to tell us what area you live in, what the soil type is where the project is being built, and exactly what type of PT wood you have.
Really though, if the grading is right, so as to drain water away from the posts, and the lumber is good, I don't think you have a problem. The method you described is in common use here; personally, I like to put the uncut end of the post into the ground. The metal post anchors hold the wood up off of the concrete, which is inherently damp.
Edited 4/12/2006 10:37 pm ET by Matt
Actually most of the PT framing wood treated for ground contact (.40 and above) out here is Western Hemlock, Sitka or Engleman Spruce, Pine or one of the true firs, which all take treatment as well as SYP.
Doug fir is treated, but seldom ensized and I haven't seen any .40 doug fir in a long time....the non-encized Doug Fir material is often structural select and is used for decking, handrails, fascia stock etc. You're right, though, that the cellular structure of Doug fir limits penetrations of treating chemicals.
The other application of treated Doug Fir is for pilings, bridge timbers, power poles and RR ties, but those treatments are creosote and the encizing and treatment is really heavy.
Personally, I avoid exposing any PT wood to ground contact that is supporting a permanent structure.
The poster who mentioned a lifespan of PT wood at 90 years was misinformed; the treatment plants will only stick their necks out for 40 years or less. (In part, that might be because the two local treating plants here are the primary PT suppliers to Hawaii and the South Pacific, where the termites are merely slowed down by the poisoned wood).
As Andy Engel cautioned, cut ends with exposed endgrain can be the Achilles heel of PT wood; When PT wood posts are set on concrete footings or pier blocks ABOVE THE GROUND, it's a good practice to set the uncut, treated end on the concrete, rather than the cut end. You can always paint or soak the cut ends in green death or some other canned treatment, but it will never achieve the level of treatment that is achieved in the pressure treating process.
>> Actually most of the PT framing wood treated for ground contact (.40 and above) out here is Western Hemlock, Sitka or Engleman Spruce, Pine or one of the true firs, which all take treatment as well as SYP. << That's interesting. I knew it was one of those "western woods' - just didn't know what one(s). Are those species you mentioned incised when treated?
BTW - have you ever heard of "mid-depth" rated wood as the OP referred to?
Edited 4/13/2006 6:37 am ET by Matt
"Mid- depth" treatment is a new one on me....may be such a thing; just never heard of it.
The species I mentioned are usually incised, but I've cut hemlock and spruce on my own mill and had it treated without the incising and penetration was pretty good.
Edited 4/13/2006 8:34 am by Notchman
If the species you named absorb the treatment as well as SYP, why would they incise it? Why don't they incise SYP? - or at least I've never seen it.... Maybe in the highest saturation rages ? (.80)
The stuff I had treated was for fence rails and facia stock. While I specified .40 treatment, I did not want the incizing for obvious reasons.
Since my material was batched with other product, I doubt mine would meet treatment specs the plant would achieve with incizing, which increases penetration in a given residence time im the pressure chambers.
Mine was also air dried for about a year which increases chemical penetration.
Is the pressure treated lumber commonly sold in your area kiln-dried before it is treated?
I am a general contractor & home inspector on the Oregon coast. We get 60 inches of rain a year here, so this is a good test for wood rot. If the posts are rated for ground contact, don't worry about it. The biggest concern is when someone cuts an end off & doesn't re-treat it as required. The non-treated end grain is most susceptible to rot. If it's done correctly, should be no problem. Around my area pole buildings are the most common type of shop, garage, etc. The posts are buried in the ground 5 or 6 feet with no concrete. I built one for myself a few years ago. As long as the builder did it all to the standard, you can sleep well.
I think I would fill the hole to the top with 3/4 minus and the pour a cap of concrete, about 2 inches thick extending out over the hole by 2 inches on all sides, then slope the top. this will form a roof to divert any water away from the footer.
Thanks, everyone, for contributing to this discussion. It's so interesting to see that there is such a range of comfort levels with PT wood and its ground contact application. In my offline inquiries, I've experienced the same results. Some are incredibly comfortable with warranties of PT lumber and others think it's a waste of investment not to consider some additional support.I finally got a bit more information about the company which supplies the lumber and am waiting to hear back from a "specialist." I live in Northern VA -- not far from Washington DC -- and have found that our soil can range from being really rich to really clay-like, depending on how we've taken care of it. We have had some water in our unfinished basement so I do know that, in wet years, water does hang out near the house. We do, of course, plan to address some of this with proper gutters and landscape water controls in hopes of abating this a bit.The rating we have is .40 CCA and the web site I checked -- http://www.treatedwood.com/performance -- at the recommendation of my builder suggests that it has a 60 year warranty.The solution my builder has recommended is surrounding the footings with brick, though I'm unclear on how much this brick would operate as a true solution to support the structure above if the posts failed.The best temporary solution I've seen is one which offers coating the lumber with bitumen and some sort of concrete encasement (as recommended by an engineer). It seems designed to keep the water moving away from the lumber while also protecting it.I guess, for me now, this is coming down to the most realistic expectation of how long this PT wood will truly last. If it's 60 years, I can probably look away and live with it. If it's 30, then, it seems like the solution will either a) cost a lot to fix down the road; b) become a problem for someone else or for us if we tried to sell the house; or c) be outdated anyway due to developing technologies or Acts of God that may do what the termites/rot don't!The "mid-depth" statement is something that I pulled off of our plans. It sounds & looks to be consistent with many of the installation recommendations made on these boards. As I understand it, the builder generally tends to build stronger concrete footings beneath the structure (wider or deeper than required by code, maybe?) and is incredibly confident in the technique. Even the architect who did our house went with the same footings for his new house, which is 5 blocks from ours.Thanks to all for your help on this. We're still not sure what we're going to do, but time will force our hands soon!K
If you are that worried about it and you have some slope away from the posts/footings you could install some "footing drains". I did this once for a similar situation where water would sit on top of the footings around the posts for several days as the soil didn't perk (drain) worth a flip. What I did was just got some ~1.5" PVC DWV pipe and ran a drain pipe out from each footing. Each drain pipe "exited to daylight". Then I backfilled the footers with gravel and capped it off with soil.
I seriously doubt that what you have is CCA though. CCA was phased out for residential use by direction of the EPA starting in 1/2004. I can tell you though that your PT lumber is SYP which is not the same as what they get out west as it obsorbs the PT chemicals better than most woods. The treating chemical you got is more than likely ACQ.
BTW - I lived in No VA some time ago and most of the soil was red clay with a variable depth cover of top soil. Red clay doesn't drain very well.
You are prudent to be concerned about rot, and to being prone to insect attack from ants or other insects which do not ingest the treated wood. PT will rot if it is wet, exposed to air, and warm. So, your focus needs to be on eliminating atleast one of these key factor; most likely, kept dry. Then mitigated with as much protectant as possible, not relied upon! How you do this is up to you and the builder, but if you keep these criteria in mind you will greatly reduce any rot concerns.
I would insist the wood post to footing contact point be further off of the ground. If this is beyond code, then work with the builder on costing. Ideally the wood will be 6"-8" above grade, and rest on a footing which will be sloped on top to evacuate any water which does make contact with the top of the footing. Also, make sure your metal contacts are ACQ rated, this is a must! Also, any end cuts or penetrations (nails, screws, bolts etc.) need to be re-treated before being put insitu. Lastly, air movement is important if moisture is a problem. The wood will not rot if it goes through rapid wet dry conditions. Air movement around the post will provide the all important rapid dry conditions required to keep wood from staying wet. If the wood cannot get wet from precipitation, ground contact or condensation, then the air movement is no longer as important.
If your addition is greater than one story, or holds greater than normal loads (waterbeds, gold bars etc.) than the footing does seem inadequate. Check your code requirements for yourself, ultimately, the more you know, the better off you are.
As the addition is attached to the main dwelling, which has a full foundatiion, then you want to be sure the two do not move independently of each other. This makes the footing detail very critical. If they do move independantly, there is a strong opportunity for fastener failure, or roof membrane failure as the two pull in opposing directions. Engineering wise, the fasteners are made to sustain very little "live" loading, and would certainly be exposed to shear and tension if the two structures move in different directions!
If your area is prone to frozen ground conditions, this footing will heave, and should extend below the deepest potential frost point AND be surrounded with a slip sheild to prevent adfreezing to the footing. Again, know your codes. I always encourage my clients to know as much as possible for themselves, even if they never touch a single tool throughout the entire project. I always share my knowledge, and explain why the codes are what they are.
It can also be prudent to include an appropriate load bearing screw jack point to the post system. I do this at the top connection of the post to the subframing. This will allow you to react easily to any leveling that may be required in the future, or ease post replacement if required (rot, insects, structural failure of the wood or footing).
To be fair, your situation is not necessariy going to fail, but as a detail obsessed builder, this is the sort of detail that seperates a good builder from an excellent builder.
Quality building is based on a sound understanding of building science, a commitment to doing the right things, the right way, and an understanding of the reasons behind the code requirements, and the enginnering properties of the materials available for use. Its not a slogan, or a trusting smile and the right words, at the right time! It's in the details.
Good luck, Glen in Canada
I'm guessing you ment that post for the guy with the question, not me. BTW - what area of canada do you live in?
Here's a product I ran across while adding a masonry porch at the front entry of a house. I was looking for away to seal the concrete beam and brick ledge which would be partially covered by our slab and later the mortar bed and stone.
Its called bentoseal made with betonite, its a paste like consistency you trowel on then backfill, when exposed to water it expands and seals areas where water may migrate into.
I pulled out the can I own (3 gal),heres there description
"bentoseal is a trowel grade sodium bentonite and butyl rubber compound with the consistency of thick grease. bentoseal swells upon contact with water,forming a tight pressure seal when used in a confined condition."
Its manufacturer is colloid environmental technologies
They also make a product called volclay which is basically corrugated card board,the corragations are filled with bentonite clay.Its fastened to the exterior of below grade surfaces before backfilled. the water content in the soil expands the bentonite in turn sealing out water,obviously the card board disenagrates
Edited 4/13/2006 8:19 pm ET by floor sweeper
Edited 4/13/2006 8:21 pm ET by floor sweeper
If it's PT southern pine, I wouldn't worry much. The big caveat would be to make sure that if the posts are cut, it's the factory end that's in the dirt. The preservative rarely if ever gets all the way into a 6x6. Cut one through the middle and you'll find wood that's yellow, not green, because the preservative didn't get into th middle. Most PT wood failure I've seen began at cut ends.
One problem you're likely to have, if you paint the wood, is that the constant wicking of moisture through the end grain will pop the paint in a few years. And, since the wood is likely to be soaked when you get it, you won't be able to paint it with any hope of longevity until it's dried. Two things to do. First, seal the end grain with at least an alkyd based paint. Epoxy diluted with alcohol or acetone would be better. When the wood's dry enough to paint, sand it first with 60 grit paper. Even exposure to two weeks of UV can mean the difference between paint staying there for 20 years or 4 years. Sanding removes the sun-damaged wood, and exposes a surface that will hold paint. And the Forest Products Lab of the USDA has found that sanding with 60 to 80 grit paper provides the best surface for paint adhesion.Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Yes, I agree. As long as the factory treated end is down, assuming a suitable grade of treatment you are okay.
I would be worried about the nails used to attach the metal post anchor to the post, as they will allow the inner, untreated part of the post to rot. You most likely need the nails to prevent the dreaded "uplift", unless 24 in penetration is eneough for uplift.
Should have used a concrete pier, with wood above grade.
Locally the appraisers use 20-30 years as the expected lifespan of pole barn type buildings. The main reason being that the posts rot at ground level in a manner as described by Piffin, and then slowly sink into the ground.
I have had to remove and replace .40 treated 6x6 post in buildings that are less than 20 years old due to moisture and decay. I have inspected polebarns that exhibit pole rot at a young age. The consistency of treatment is variable.
If I was in your situation I would ask the builder to add temporarily support at one post at a time, cut the post off at a height above finish ground elevation.
Then confirm the proper size of the needed footing for the structural load, replace the existing if needed.
Set a sonatube with a rebar cage to the footing and pour a concrete column to stand above grade and support your structural post. That way you can keep the houses feet dry and safe from hidden decay.
Just a personal opinion..............Iron Helix
You are correct to be concerned.
Two problems here.......both of which could have easily been avoided by using an 8X8 masonry pier to the floor level.
1. Pressure treated wood changed recently from CCA to the new stuff. I do not think anyone is that familiar w/ the longevity of the newer PT. If history tells us anything...(paint, floor finishes, after mkt wood treatment) it is that longevity suffers the most when a product is modified for "environmental reasons".
2. I personally would not be comfortable w/ grade contact of a wood column. All the grade contact PT wood foundation designs are "life spanned" based on having the lumber laying FLAT on "dry/ well drained soil"....you have a 30 sq inch area of END GRAIN sitting in wet soil....with a concentrated load on it.
I would consider encasing it in a load bearing masonry (poured conc, or bricks) built-up pier.
>> 1. Pressure treated wood changed recently from CCA to the new stuff. I do not think anyone is that familiar w/ the longevity of the newer PT. If history tells us anything...(paint, floor finishes, after mkt wood treatment) it is that longevity suffers the most when a product is modified for "environmental reasons". <<
Actually, "the new stuff", ACQ treated wood, has been around for over 15 years.
I've read to the last post and no one has mentioned salt water treated CCA timbers (actually, usually posts) that are still available. Do you live near the ocean? If so, contact a marine construction company or their supplier. They will have CCA treated posts used for marine construction and unless your soil has barnacles and toredo worms you should be fine. Still, I don't understand why they didn't specifly concrete. It ain't that hard.
I live near a seaport and, in the past I was involved in the construction and repair of port docks.
All the timbers we used were heavy creosote, which, until recent years, carried a heavy level of Pentachlorophenol (now banned).
Most of the pilings were also creosote, but in some areas of the bay, point of refusal was over 90 feet so, in recent times, dolphins and pilings were and are constructed of prestressed concrete...concrete pilings on one array of Bulk carrier bumper dolphins we built were delivered at 120 feet and then cut to desired elevation at POR.
Wood pilings in the above applications had to be spliced with steel couplings and were often problematic when driven at the angles required for a dolphin.
I haven't seen the salt treatment around here, but I have heard of it.
There are some nasty (but effective) chemical "salts" (named for the chrystaline form they come in) that are used in existing power poles to extend life of the poles, but I believe those have a rich arsenic and copper component.
This is a little bit of hijacking, but if you cut prestressed concrete then it's not stressed anymore, right?
If you cut prestressed concrete you may be in for a lot of stress.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
yes, that's what I thought. I was replying to Notchman
The concrete pilings in our project were 3' hexagons with hollow centers and an array of rebar in the concrete.
It's my understanding that the tensions rods were removed prior to shipment and after a scheduled curing.
So, I would surmise that the "prestressed" aspect was to ensure density during the cure.
This was all about 16 years ago, so some of the specifics are too hazy in my memory to relate with great authority today.
Each of the bumper dolphins had 16 of these piles and a large concrete cap was formed and poured on top. When the piles were cut to length, the rebar (2'' IIRC) was left proud and bent and tied into the rebar in the cap. The caps measured something like 10'W X 14"L X 8'H.
The piles were driven with a large vibratory barge-mounted pile driver out of Seattle.
Just for your interest, four dolphins were constructed. Attached to the outboard face of the concrete caps were large, spring mounted bumpers with a facing of some kind of heavy rubber matting to protect the ship hulls.
Cost of the project was $750,000.
Incidently, The Old Growth sawmill and the shipping facility it served are long gone. A local indian tribe has the property, which consists of a casino, an RV park under construction and the soon-to-be-developed site of a Home Depot....God help us all!
Edited 4/15/2006 10:28 am by Notchman
Build a little "tree well" type structure around each post.
"Doubt is not a pleasant condition, but certainty is absurd." Voltaire