Piers for a small Cottage.

[Ken S. Tucker]

Purchased a recreational lot in BC, but it's zoned R1 residential, so BC building code applies. Want to build cottage, size 20'x20'.

The lot is flat on dense gravel, but it has to much clay content to be used for an aggregate in a concrete mixture, and the nearest aggragate supplier is 30 miles away and charges $100 min, for my 12 piers, 2' into the ground per code, to deliver, then of course I mix and pour using sonotube forms.

The bearing pressure of the lot gravel is rated

150 KPa ~ 3,000#/sq ft, ascertained by diggings 4' down for septic approval, and has fast drainage.

What do you guy's think about using Pressure Treated wood for the piers instead of concrete?

I'm figuring, a slab of PT lumber at the bottom of the hole spreading the area to about a sq ft, with a 2' fastened 6"x6" PT vertical short beam, as my pier, upon which the floor beams sit.

Naturally, I'd be careful and apply a serious tar resin to the PT and end cut's to avoid rot.

Comments appreciated... Thanks again Ken S. Tucker

[Bob Morrison]

> I'm figuring, a slab of PT lumber at the bottom > of the hole spreading the area to about a sq ft, > with a 2' fastened 6"x6" PT vertical short beam, > as my pier, upon which the floor beams sit. >

Ken:

While I like Don's solution, I have another idea. Use the auger to dig an 18-inch diameter hole about 3 feet deep. Put about 6 inches of mixed concrete in the bottom (I prefer that you mix it ahead of time rather than pour water over the dry mix in the bottom of the hole). I recommend adding a shovel full of portland cement to each bag of premix to get a little higher strength.

When the concrete is hard enough to bear the weight of a post -- usually the next day -- set some 6x6 pressure treated posts in the holes and prop up to they are plumb and square.

Now, here's where my method radically differs from Don's: the gravel has a high clay content so it should be ideal for tamping and compacting. Using the material you dug out of the holes, put it back in around the posts tamping it down as you go. Put no more than 6 inches of material in the hole at one time. You will need to rent or buy a tamper. These suckers weigh about 20 pounds, which doesn't seem like much until you've lifted it a few hundred times.

As for the lumber, get material that is especially treated for embedded post use. The normal stuff you buy for exterior decks won't do. Here's my spec:

Embedded poles shall be pressure treated per AWPA C23 for round poles to a retention of 0.60 pcf and AWPA C24 for sawn poles to a retention of

0.80 pcf. Cuts and Holes in all pressure treated members shall be treated after fabrication with 2% Copper Napthenate in accordance with AWPA M4.

Once the holes are dug you should be able to spread this work over several weeks or do it in one long weekend.

[Chris Gyotar]

I would consider an alternative to pressure treated wood as there is some question of the arsenic content leeching out. Perhaps there is a process that does not use arsenic or you might consider using steel posts? This is rendered moot if there is sufficient airflow around these posts to dilute the arsenic. Just my two cents.

Chris

[Ken S. Tucker]

contamination

application to

Ok I'll use Saran wrap. Telephone poles aren't on Greenpeaces list .... yet ???

Auger won't work, rocks in gravel half the size of my head, (the one on my shoulders), also only need

2' deep in this area, so spade digging is easy.

connect 6x6

liberally

I wanted to do something like that, but that plan needs to be certified by an engineer, because it's not "WESTERN CONSTRUCTION", which is based on compression force. I would prefer your system but it's based on

*shear* force, recall I'm in BC Canuckistan, where you a pay a bribe to get somebody who ain't stoned.

permitting.

Don't forget lost body parts, I'm using a shovel, so add another case of brew.

[Chris Gyotar]

LOL, there are many documented cases of stupidity in the construction field as you are well aware of. I recall my proffesor telling how he hired his not so bright cousin to treat the lumber in a large pit of solution because everyone else had health concerns :)

Why is that? Are there other health concerns or practicality issues?

Chris

[Chris Gyotar]

Spelling error? Wow that's a great reason to evade my question.

The joke is you. You and your bourgeois crap can collect dust in my kill file since you clearly have nothing relevant to say.

Chris

[Bob Morrison]

Don:

I concur. I think we are mostly on the same page about how to get this done.

In this instance I definitely agree. Having someone with the right tools and experience to set the the poles is a real plus.

[Bob Morrison]

The treated wood available to retail consumers no longer contains arsenic.