Concrete vs Stick build

Started by Net_Eng, March 16, 2011, 09:56:52 AM

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Net_Eng

What do you guys think about the difference in longevity, price and reliability between concrete and wooden structure?


jbos333

Hi Net-Eng.....

I don't have the answer for you on this one, but I am curious as to the answer myself....

I have been considering a 24 x 40 earth bermed home "basement with a roof", maybe with attic trusses to make a "first floor", vs. a pole type structure with a slab.

So I hope someone has some figures for you AND I.

I can tell you I got a quote for a poured 8' basement with footers for about $8500.00. Excavation and drainage another $5000.00. Floor slab another $4000.00. So, around 17,500.00 minimum for a 900ish s.f. floor space. I also got a quote on attic trusses for 1/2 and scissors type for the other 1/2. around $3500.00 delivered.


fistbump

The concrete should last longer but it is expensive and there is upkeep to do on it. My cabin had 60 year old concrete that held up pretty well in the basement but it is starting to leak bad. I paid to have a dry lock floor put in over it. It started leaking again right after my year warranty expired on the flooring. A wooden floor would probably by rotting by now though. If you go with concrete make sure they do a great job on the drainage or you will be paying for it later.
Find real estate for your cabin.

Net_Eng

The pricing I got for a 30x40x9 basement was 26k with ICF and 18K poured. For a 30x60x9 its 35k with ICF. I like the ICF because apparently its more durable.

All of comes with 10" thick walls, 10" stones at the bottom, footings and a sump drainage without the pump.

Squirl

Interesting debate.  I read that modern Portland cement is actually a chemical process of curing.  As it cures it hardens over a lifetime. It never actually stops and one day will eventually crumble.  I have read debates of the time that this takes can be 50-100 years.  Although there are probably older examples, I haven't seen any, because 100 years ago stone was the most common foundation material.  Which to me seems like it would be a moot point of the lifecycle of the wood if the foundation starts to crack and crumble.  Technically the enemy of wood is water.  There are wood buildings that have lasted hundreds of years, but they take maintenance or someone living in them that long. 6 one way half dozen the other.  They will all last you lifetime.


John Raabe

The Romans were the first to use concrete in structures. Some of these are still in service. Modern concrete continues to harden even after the first 100 years.

The problem with concrete walls in residential structures is:
• It's inflexibility - You don't easily change your window and door locations. Inexpensive remodels are out.
• It likes to transport moisture from the wet side to the dry side. You have to be very careful to overcome this and have your solution last for the life of the structure.
• It's heat conductivity - You want insulation in most climates. When you combine that with...
• Where do the utility lines go? (power, water, plumbing, etc)... you often build an insulated frame wall on the inside that could hold up the roof on its own.

I still like the PT wood foundation system, but not many folks here have built it. It overcomes many of the drawbacks above and can be built by owner-builders. I have details for this basement system in the Universal Cottage plans.


None of us are as smart as all of us.

MountainDon

I'd like to see someone do a PT wood foundation here.  Hint, hint.   ;)
Just because something has been done and has not failed, doesn't mean it is good design.

umtallguy

modern concrete has had the fatal flaw of steel rebar, eventual that steel will rust enough to break the concrete... Now with basalt products on the market that will be eliminated as they take over market share.

I priced out ICF yesterday for my plans, and just the forms would have cost as much as lumber sheathing and insulation....

What I really want to build is a monolithic dome, but they require expensive equipment.

Squirl

Quote from: MountainDon on March 16, 2011, 04:33:14 PM
I'd like to see someone do a PT wood foundation here.  Hint, hint.   ;)

I know this might be a little bit of a drift, but this prompted me to look into this option and I am heavily considering it.  My questions are about longevity, and normal scenarios that this type of foundation is supior for.  One of the pain in the butt parts of my research seemed to be the requirement of all stainless fasteners.  Off of the guides I found here:

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_4_sec004_par039.htm
and FIGURE R403.1(2)
http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_4_sec003.htm

So far my estimate is for a 20x30 single story.  I figured a 6ft stud height for 4ft to the frost line and 2ft of crawl space above.  So I estimated using a 2x6x12 cut in half to reduce waste.  At 100 ft of outside wall area at 16" O/C, I came to a rough estimate of 75 studs and add in an extra five to make it a round 80, divide 2 studs per board at $8.00 each for around $320 for studs.  Bottom Plates 10- 2x6x10 PT at $7 each for $70.  A footer plate of 10-2x8x10's at $10 for a total of $100.  Double top plates of 20 – 2x6x10 at $7 for $140.  I figured 600 sq. ft of plywood at 32 sq. ft. per for 19 sheets of ½" PT at $30 a sheet for $570.  Also a 6x16x100 trench of gravel for 66 cu ft of crushed gravel. They sell crushed stone at $250 for 12 yards delivered.  I would be using the rest on the road anyway, so about $60 for a  crushed stone footing.  So an estimate of $1260 for a PT foundation.  I had an estimate of materials for a poured 6ft foundation walls and footing at $2500 to $3000.  Thoughts?

One of the big advantages I could see is speed of construction.  What other advantages/disadvantages am I missing?


jbos333

Squirl,

I have done a little research on PT foundations. It does appeal to me, however I still can't get past the idea of putting wood in direct ground contact, even though it's treated.

A guy I work with has a family member who built a 2500+ sf home locally on a PT foundation, around 5 yrs. ago. He was over for there for Christmas, and was in the basement, which is finished, and he said it was nice and dry and comfortable.

John Raabe

The PT foundation system uses foundation grade treated wood put together on well drained gravel footings with a drainage plane water barrier on the outside and drainage rock down to footing drains. The wood itself is not in contact with water under conditions where it could likely rot. Typically a poured slab at the bottom of the wall provides a compression "backstop" to the bottom of the wall's desire to kick in. There are ways to do this with a wooden floor diaphram as well.

This is considered a permanent wood foundation (click: PWF).

The fasteners need to be rated for the PT wood you are using. Stainless steel is the gold standard here. In some cases the newer zinc coated steel treatments can be used. Check with the lumber supplier.
None of us are as smart as all of us.

Squirl

Thanks for the additional information.  I was not intimidated by using wood from seeing docks that have lasted 50-100 years. It is starting to sound like a less attractive option for my needs.  The largest advantage over concrete that the website posted was no need to frame a basement and I am only going with a crawl space.  Also I had missed the requirement for treatment.  The big box stores have a .2 lbs./cu.ft while the article you gave says .6 lbs./cu.ft. Triple!  That sounds like it would start to push up the price by a lot.  I assume the slab is for foundations that don't have fill on both sides?  I don't understand kick back if there is equal pressure of earth on each side of the wood. 

In the code it said that stainless 304 or 316 are the only kind of fasteners approved for use below grade.


MushCreek

I don't think it matters to most folks here, but I would imagine the re-sale value on a house with a PT foundation would be poor. I'm very tempted, as it would be perfect from a carpenter's viewpoint, but i remain unconvinced, especially as I am building in the Deep South, where rot and termites reign supreme. Despite what the link says- Do you think insurance would be a problem? The insurers have gotten VERY picky in recent years, at least in FL.
Jay

I'm not poor- I'm financially underpowered.

MountainDon

Big Blue and Big Orange do not stock the 0.60. Not around here anyways. It usually has to be ordered in or bought from a PT wood foundation specialist. I believe it is also still the CCA variety. So yes it probably costs a premium. But it is superior to any off the shelf .20 or .40.
Just because something has been done and has not failed, doesn't mean it is good design.


Squirl

Not around here either.  I found this.
•Above Ground - 0.25 - Decking, fence boards, hand rails, deck supports
•Ground Contact Fresh Water - 0.40 - Fence posts, landscaping, piers, docks, etc.
•Permanent Wood Foundations - 0.60 - Wood foundations, crawl spaces
•Poles - 0.60 - Building, transmission and distribution poles


So it is the same as utility poles which are put in the ground with no care for drainage or water.  I have seen ones 30-40 years directly in standing water.  When I go to the beach this is one of the only types of foundation I see.  (PT post) I did a little reading and it seems that many of the complaints are that most builders treat them as a concrete foundation and don't really care about keeping them dry or don't build them with proper treatment. Mushcreek,  also I found a brochure on southerpine.com that said the threat of deterioration in the South East U.S. is High to Severe. I assume this would be taken into account for insurance, but I'm in the NE. If I was looking to build a permanent structure, I would build it out of solid stones from the foundation up to a solid copper dome roof.  Time and money don't permit that.  I would have to see what the cost is and if it is even available locally.  My recollection was that utility poles cost a fortune.

Don_P

I'll throw another kicker in there, technically the wood should be foundation grade treated lumber at .60 lbs per cuf ft retention. This is all sapwood timber. heartwood does not accept treatment chemicals, hence the all sapwood stipulation. never seen an inspector that would know the difference so you could do a visual selection if you can pick through a stack of treated. I've actually used up to 2.50 pcf treated CCA... for ocean water exposure. That's been awhile ago!

Barry Broome

I have one thing to say about CCA treated wood - as I inspect poles for a living (no pun intended). CCA treated poles (.6) are expected to withstand ground contact for 50 years (in general). I have seen some CCA power poles, manufactured in 1977, that do require some exterior treatment due to a small amount of decay at the 12-18 inches below the ground level. CCA is a good option over Creosote (as its mostly no longer available). The advantage of creosote over CCA poles is that creosote poles are more likely to bend/sway without breaking. CCA poles become very hard and brittle once they dry out from the treatment process. They are more likely to snap, but also not likely to decay with ground contact. Creosote endurance was always based on how well the pole accepted the creosote (some more than others). CCA poles seem to accept the treatment well, across the board. And you can work with CCA poles without getting covered in soot. Which is nice.
"The press, like fire, is an excellent servant, but a terrible master."

umtallguy

folks take a look at TIMBERSIL, not yet widely available, it is a silica impregnated wood...
Wont burn, is insect resistant, rot resistant... and NON Corrosive

John Raabe

Interesting product umtallguy

TIMBERSIL - a glass wood composite material.
None of us are as smart as all of us.

Triathlete

#19
Here is a quick sketch of one idea of how to construct a PWF knee wall that addresses some moisture and stability concerns within a crawl space.  There is no contact between the wood and soil.  I drew this very quickly on sketchup, but I forgot to add-in insulation, which would probably be 2" of blue styrofoam (4'x8' sheets on edge) sandwiched between the sheathing and concrete board.  I'm thinking that this would keep the moisture, cold, and vermin at bay.  The biggest concern would be moisture/humidity control within the crawl space.  This has to be thoroughly researched before construction.  This is a fair amount of literature on this topic, so you will need to do your homework to cut through what is credible and what is not.  You do not want a moisture pit under your house.


http://flic.kr/p/9rgWmR





umtallguy

yep, it is fascinating, but I havent been able to get my hands on any to play with yet  >:(

Net_Eng

What do you guys think about this garage with loft. the idea is to build something which I can use later and since I will need a garage...I think, why not start building that.

I can build a shack for about 3-4k but that could mean 3-4k into the garage. What do you guys think? how much do you think it will cost to build?
http://www.thegarageplanshop.com/6176/plan-detail/006g-0080.php


John Raabe

Just a word of caution. I have several neighbors who started building a garage/workshop as their first building but never used it for that.

Here's the story... You plan that nice functional outbuilding and about the time the place is shelled up you realize you are less than 1/2 way to the final cost and the money left for the house is looking thinner and thinner. Then, you look around and say to yourself, "I could live here!" And then you do.

Some of these projects work out better than others. They are not usually laid out for the best site placement as that was reserved for the never built house.

None of us are as smart as all of us.

Don_P

Ditto, I've seen that happen several times, which isn't always a bad thing, less is more.
I'd lose the dutch hips and run a typical gable out to the ends of the building, cheaper and gives more space upstairs. This could be easily built with storage/attic trusses and would go up quickly.

Net_Eng