Tag Archives: concrete footings

Pre-Drilling, Housewrap, and Concrete Footings

Today the Pole Barn Guru answers reader questions about pre-drilling steel panels, the proper use of house-wrap and weather resistant barriers, as well as concern for the effectiveness or fresh concretes ability to withstand compression.

DEAR POLE BARN GURU: What size hole should I predrill in panels for the #12 diaphragm screws? Thanks! JOSEPH in KIOWA

DEAR JOSEPH: From Hansen Pole Buildings’ Construction Manual, Chapter 2:

 

“For pre-boring nail holes, 7/64” and 1/8” bits are required. Same size bit can be used for pre-drilling steel roofing and siding.”

 

DEAR POLE BARN GURU: Having read all of the info relating to insulating and am still confused. Main question is my entire 40×48 was wrapped in Tyvek including the roof. Now am trying to figure out if and how I can install a vapor barrier for the roof? Am planning to put in a ceiling with blown insulation above it and would like some options for the vapor barrier. Not sure if the roof Tyvek is a help or a hindrance. KEVIN in MALAD CITY

DEAR KEVIN: I’d like to find builders who are using Weather Resistant Barriers (WRB) under roof steel on post frame buildings, thinking they are installing a vapor barrier, and slap them silly. They have totally wasted their client’s hard earned money and, as in your case, have created a hindrance. Your only real solution is to remove Tyvek from under roof steel and replace it with an actual vapor barrier (one with a thermal break). You might see if a local spray foam installer would be willing to flash spray two inches of closed cell foam on underside of your building’s WRB.

DEAR POLE BARN GURU: My contractor poured concrete in each hole for a 30’ x 32’ pole shed and about 4 hours later started setting poles and put the entire frame up yet that same day. Can the concrete actually cure that fast or should I be concerned? PAUL in MITCHELL

DEAR PAUL: I am guessing you are talking about concrete poured for a footing pad under the columns.

Concrete gains its strength with time after casting. The rate of gain of concrete compression strength in higher during the first 28 days of casting and then it slows down. The compression strength gained by concrete after 24 hours is only 16%!

For practical purposes, a four hour old concrete footing is virtually worthless. Yes, you should be concerned.

 

Double Skirt Boards, Siding Options, and Foundation Plans

Today’s blog discusses double skirt boards, siding options and foundation plans.

DEAR POLE BARN GURU: The pole building garage at the house I bought has two skirt boards. Can I remove the interior board to remove the dirt easier and put quikrete in its place. There is a 5” gap between the wall and the floor. The previous owner started putting quikrete in some places. Looks like the floor was put in before the building was built. KENNY in PARKERSBURG

 

 

 

DEAR KENNY: The Hansen Pole Buildings’ warehouse has the exact same situation. The interior splash plank is doing nothing for you or your building, feel free to remove it.

 

 

 

 

 

DEAR POLE BARN GURU: Can the steel exterior panels be omitted? I plan to install log siding and false log corners to match the appearance of my new log home.
Thanks BILL in WILTON

Roof Only PorchDEAR BILL: In short, yes – we can provide a building ready for you to side. What we most typically provide is 7/16” thick OSB over bookshelf girts 24 inches on center, with housewrap over the sheathing. If your false log siding can structurally provide resistance to shear, the OSB could be omitted, however this would not be my recommendation.

 

 

DEAR POLE BARN GURU: Do you include foundation plans with your kits? JOE

DEAR JOE: All Hansen Pole Buildings come with complete engineered foundation plans based upon your specific building, upon your site and reflecting the soil bearing capacity confirmed by you.

 

 

A Concrete Backfill Dilemma

Clients make for the best blog article subjects, here we have client Dan at a relative loss as to what to do about concrete backfill dilemma in and around his building columns.

DEAR POLE BARN GURU: Hi there!

 So I am about to receive everything for a 22x34x10 pole barn. The plan is to add a 4” floor after the roof is on…

 So here is my dilemma:

 The way I see it, I have a few options in installing the poles.

  1. The way you describe in the manual. 40” deep, set poles plumb, fill concrete, back fill to the grade. This requires me to probably bring in a concrete truck as I have 10 holes and hand mixing might be a pain. This is probably $500?

 

  1. A friend of mine builds barns and the guy he works with does it like this. Digs down, pours one bag of 80lb concrete and then backfills to grade. Post sets on the concrete. 

 

  1. That same friend wants his ideal barn to go like this: Dig down 36”, fill with concrete up to the level of the eventually poured floor. Each pier is the same elevation. Put a J hook in, get a post bracket and position the post on that. I did a deck this way and its nice because I have some movement. This way, I can square the bottom and tops as I put on girts. 

4.   My new way of thinking is similar to #2 but putting the posts in a post protector. This is a                 happy medium between cost and time. 

 Are any of these truly red flags? Is #4 a don’t do? Wouldn’t the posts eventually get rebar into the 4” thick floor to prevent uplifting? 

DAN in QUAKERTOWN

 DEAR DAN:  (1) Not deducting for the space occupied by the columns it would take 37 cubic feet (1.37 cubic yards) of concrete to backfill your columns. Hand mixing would be an absolute pain. You might see if your local pre-mix company could throw on a little extra concrete when they are pouring another project in the area, in order to save trucking costs.
(2) Absolutely not acceptable. There is no way 1/2 of a cubic foot of concrete becomes any sort of an adequate footing. If you are lucky it would give you a 14 inch diameter footing six inches thick. This would be close to the equivalent of just placing the column in the hole with no concrete at all! Two 80 pound bags of Sakrete could provide an adequate footing to prevent settling, but would do nothing for uplift (read lots about Sakrete for post holes here: https://www.hansenpolebuildings.com/2012/11/concrete/).
(3) The brackets your friend is talking about using are probably inadequate to carry the horizontal loads. There are brackets made specifically for the post frame industry which you could mount a column to a concrete pier (https://www.hansenpolebuildings.com/2012/09/concrete-brackets-2/). If your pre-mix company wants to charge a premium for a “short load” you could always just order more concrete and backfill the holes entirely with concrete and avoid the brackets altogether.
(4) A post protector is not going to change the inadequate footing from door number 2, however it does add the cost of the post protectors.

In my humble opinion, the only two adequate choices are #1 first, followed by #3. The rebar tie-in to the concrete slab may very well be adequate to prevent uplift forces, however we design for the worst case scenarios – where the concrete slab does not get poured immediately, or the rebar hairpins get left out.

 

Mike the Pole Barn Guru

Pole Barn or Block Foundation?

A prospective client recently posted this question about block foundations:

Barn with Rock WallsOur family farm was started around 1850. During this time there were 12-14 barns and 1 house. Most barns deteriorated due to bad roofing. But we’re talking about stuff that lasted 100 years and some longer. We still have 4 barns left and the house which are all sitting on stacked 36″x36x12″ thick hand cut stone. My question is im getting ready to build a new building so is this type setup better than a standard pole barn? If so why does everyone then do pole barns? I could do a block foundation vs rock if this is a better way to go. The equipment building will board and batten with concrete floor and be 60×40 or so in size. Im looking for longevity and want to avoid rotting post. 

Thoughts?”

100+ years ago, a reliable pressure treating process did not exist which would preserve wood (timbers/lumber) embedded in the ground. As a result, farm buildings were constructed similar to what is described. The stone piers were probably adequate in area to prevent buildings from settling.  However they would prove no resistance to either frost heave (in areas which have frost issues), or uplift situations. If stone piers were the solution, they would be both Code conforming, as well as used extensively for new construction.

Post frame (pole buildings) have decades of reliable performance. They are the most economical permanent structure which can be built.

Although properly treated timbers will easily outlive any of us alive to read this today, there are many lumber yards selling pressure treated wood which is not designed for structural in ground use. The Building Codes require any wood which will be embedded in the ground, for foundation purposes, to be pressure preservative treated to a UC-4B (UC is Use Class) rating.

Look at the tags on the treated lumber on your next visit to a lumber yard or big box lumber provider. If the tags say UC-3 or UC-4A, they are not designed to be embedded in the ground.

Not convinced UC-4B will last? There are several manufacturers of plastic sleeves, which can be placed over the base of the columns, isolating them entirely from the surrounding soils.

Concrete footings are not inexpensive!

There are tremendous, and in my mind unnecessary, costs involved in pouring concrete footings and properly constructing either a concrete or block foundation to place a building on. There are engineered brackets which are designed to be poured into the top of foundation walls (again, beware – most post base brackets are not designed to withstand the moment loads induced into them by bending columns). Taking an educated guess, they would probably be inadequate with a block foundation, unless the block had adequate rebar and was poured solid with concrete.

Steel wins hands down for durability and longevity

If considerations include cost, being maintenance free and longevity, in my humble opinion board and batten siding is probably not the most effective design solution. I made the error of siding two of my own buildings with cedar siding, and after twenty years of having to solid body stain them – repeatedly, I would never do it again. Painted steel siding is without question going to be the most cost effective and durable design solution.

Concrete Pier Design

A Hansen Pole Buildings client in California has just today approved the plans for his new post frame building and poses the question:

“We are in a no frost area with no snow load, so why are the concrete piers so

large and deep??”

In response:

“The column embedment (depth and diameter of the holes) has to resist several forces, including:

Concrete PierResisting uplift – the columns, their encasement (the concrete attached to the base of the column) and the “cone” of soil above the concrete bottom collar, must have sufficient mass to keep the building from being literally “sucked” out of the ground.

Resisting overturning – prior to the engineering studies done over the past few decades, the “rule of thumb” was 1/3 of the column should be below grade. Modern research and technology has allowed this design to be far more scientific.

Keep the building from settling – while you state your building has no snow load, the information on your order has your building designed for a ground snow load (Pg) of 35 pounds per square foot. The concrete piers must be able to support the dead weight of the structure PLUS any live loads which would be applied to it. These live loads include the weight of any snow, or potential snow. Your building also is designed for a light storage load attic space. Any roof truss design with this type of load must be designed to support a 10 psf (pounds per square foot) dead load across the entire truss bottom chord (12,960 total pounds on your 36′ x 36′ building) by Code. The storage area adds another 20 psf for another 8640 pounds. All of these weights have to be distributed by the concrete encasement, to the soils beneath the building, with minimal settlement.”

In areas where frost is a consideration, the column encasement (footings) must also extend in depth below the frost line, in order to alleviate frost heaving.

Continuing with my response:

“Your building has been designed with a 2000 psf soil bearing capacity, which is higher than what is allowed by most California jurisdictions. The use of this number, has actually allowed for the concrete diameters of most of the holes to be far smaller than if a lower number had to be used.”

An engineered post frame building might appear to be “just another pole barn”.  They are, in reality, highly complex structures. All of the components of the building, down to the last screw or nail, are placed through an extensive series of calculations.  They must ensure adequacy against the myriad of conditions which a building must resist in order to be Code conforming. And, most importantly, to perform admirably for not only the original building owner, but also for future generations who will utilize the building.  The concrete piers are as important as the rest of the structure they support…to be designed “just right”.