Tag Archives: Concrete

Cement Versus Concrete

Cement versus Concrete

Scraping a chalkboard (also known as a blackboard) with fingernails produces a sound and feeling most people find extremely irritating. Basis of this innate reaction to sound has been studied in the field of psychoacoustics (branch of psychology concerned with perception of sound and its physiological effects).

mr owl tootsie roll popIn response to audio stimuli, a human mind’s way of interpreting sound can be translated through a regulatory process called Reticular Activating System. Located in the brain stem, the Reticular Activating System continually listens, even throughout delta-wave sleep, to determine importance of sounds in relation to waking cortex or rest of body from sleep. Chalkboard scraping, or noises illiciting an emotional response, have been known to trigger tendencies from the fight or flight response acting as the bodys primary self-defense mechanism.

Superman has his Kryptonite, mine happens to be misused construction terms. Here, in Middle America, I have gradually adapted to term “rafters” being used for roof trusses. My favorite chalkboard scrape happens to be with use of “cement” when the correct term would be “concrete”.

Although terms cement and concrete often are used interchangeably, cement is actually an ingredient of concrete. Concrete is a mixture of aggregates and paste. Aggregates are sand and gravel or crushed stone; paste is water and portland cement.

Cement comprises from 10 to 15 percent of concrete mix, by volume. Through a process called hydration, cement and water harden and bind aggregates into a rocklike mass. This hardening process continues for years meaning concrete gets stronger as it gets older.

Portland cement isn’t a brand name, but a generic term for a cement type used in virtually all concrete, just as stainless is a type of steel and sterling a type of silver. Therefore, there is no such thing as a cement sidewalk, or a cement mixer; proper terms are concrete sidewalk and concrete mixer. I rest my case.

 

Column Hairpins, Going Bigger, and Cutting Corners

Today the Pole Barn Guru discusses Rebar hairpins, a bigger build, and cutting corners on the construction process.

DEAR POLE BARN GURU: Hello, regarding the column to concrete hairpins. I’ve talked to a couple different contractors and they both have cringed when I discussed tying the pad to the columns. They say around here everyone uses a floating pad to avoid concrete cracking. Is there another option to meet the design requirement? Thanks, HANS in PLYMOUTH

DEAR HANS: If the contractors are cringing from hairpins it is from one or more of the following reasons:

a) They have not placed the bottom of the hole below the frost line,
b) They have not adequately placed a concrete collar around the base of the column,
c) The site has not been adequately prepared to minimize ground water below the slab,
d) The site has not been properly prepared to accept the concrete slab.

In order to meet the design requirements of the engineer of record, the hairpins are a necessity.

P.S. Every slab is going to crack, it is properly controlling the cracks which makes for a good pour. By using zip strips, expansion joints or saw cuts no more than every 12 feet for a nominal four inch thick floor, cracking can be localized to these points.

DEAR POLE BARN GURU: As I was warned, my barn has proven to be too small. Can I order an extension or a second building and just extend my current 30×32 Hansen pole barn an additional 20 feet? Thanks TJ in SPOTSYLVANIA

DEAR TJ: I know this is difficult to believe, but you are the first person to ever have this problem. No, not really, it is a common occurrence and I have been guilty of it personally. Whatever one constructs, it seems the possessions increase to fill the available space plus 10%.

We can have designed for you an addition to increase your building length. Your Hansen Pole Buildings’ Designer will be in contact with you before the weekend.

DEAR POLE BARN GURU: My builder did not use the tape to seam my insulation. Short of removing the entire roof, can I tape seams from bottom and be ok? Is the taped seams purpose to stop heat and cold air from clashing to create moisture or is it to catch moisture that is going to accumulate no matter what?

2nd question. The book or plans said for the ridge cap to use 1/4 screws. We do not have any and they would be too short anyways because of the foam that goes under the ridge cap. What is the proper size screw to use. TALMADGE in WARRIOR

DEAR TALMADGE: It is aggravating when builders are in such a hurry they neglect to do simple thing such as using the adhesive, which is on the reflective radiant barrier tab already, to seal the barrier seams. All it would have taken was to peel off the pull strip! You can tape the seams from the bottom, which is going to be a lot of work and which your builder should offer to do for you at no charge. In order for the reflective radiant barrier to function properly, it needs to create an air tight barrier between warm moist air inside of your building and the cooler roof steel.

1-1/4 inch long stitch screws were furnished to attach the ridge cap, as well as corner and rake trims. They should be plenty long enough.

 

 

 

A Door Guide with a Roller, When to Pour Concrete, and Bedrock Anchors!

DEAR POLE BARN GURU: I am looking for a bottom guide for a sliding barn door. I was hoping to get a guide with a roller vs. just a roller. I noticed some guides trap the roller in a channel on the bottom of the door. I would like to know if you have that and where to purchase in Lower west Michigan.

Thanks, GERARD in PLAINWELL

DEAR GERARD: I have found the very best sliding door guide systems do not use bottom rollers at all. Known as “stay rollers” the bottom rollers tend to be problematic, especially in tough climates or when large animals are present.

Figure 27-6

The most secure and effective method utilizes a bottom girt for the door which is most typically a galvanized steel channel 1-1/2” x 3-1/2” (think of a steel stud) with a slot in the 1-1/2” face towards the ground. A galvanized steel “L” is mounted via brackets to the wall in the direction the door slides open. The upward leg of the L engages with the slot in the bottom of the lowest sliding door girt.

This design solution provides stability for the bottom of the door, preventing it from coming away from the building, or slapping against the ribs of the steel as it opens. Hansen Pole Buildings does not provide sliding door components other than with the investment into a complete post frame building package. You might try the ProDesk at your local The Home Depot®, as they should be able to order the parts in without you having to pay an onerous amount of freight.

 

DEAR POLE BARN GURU: Would I have the concrete slab poured before the building is erected or pour the slab after the poles are installed? Thanks. JOHN in REMER

DEAR JOHN: One of the beauties of post frame construction is the ability to be able to pour your new building’s concrete slab on grade at any time after the columns are placed in the ground. My personal preference is to at least wait until the roof is on – as it provides greater protection from sudden unexpected rainstorms as well as sun. The best time to pour (in most situations) is after the building shell is fully completed. Premix concrete trucks do seem to have an affinity for running into building columns which are not part of a wall.

 

DEAR POLE BARN GURU: Dealing with a site that is less than 20 inches above bedrock and is a wet environment. Frost line construction standards normally require 48 inch depth. What foundation, site prep concerns are relevant. Hoping for a barn about 30 x 40 x 12 RON in ONTARIO

Footing DetailDEAR RON: Code specifies the depth of foundations (in this case your columns) must be either below the frost line, or to solid bedrock. You will want to discuss your particular site challenges with the registered design professional (RDP – architect or engineer) who provides the sealed plans for your building. Our engineers will often solve this anchorage problem by having you drill holes into the bedrock to epoxy in rebar pins which will be embedded into the columns, then backfilling the holes with concrete. To minimize potential frost heave issues, you will want to read my articles on site preparation (use the search bar at the upper right of this page) – as you will want to remove any soils which could contribute to heaving.

 

Fall Up, Go Boom

Fall Up, Go Boom

What? Sir Isaac Newton pretty much confirmed things do not fall up.

Well, this building did not actually “fall” up – it was sucked out of the ground. How would I know this? Look at the ends of the columns which are lying on the ground. There is no concrete attached to the bottom of the columns, nor is any method for preventing uplift even obvious to the more than casual observer.

 

In review of the NFBA (National Frame Building Association) Post-Frame Building Design Manual (January 2015) the issue of column uplift is all but ignored. Beginning with the end of Page 5-37, it is concluded two pages later. Options for preventing uplift are really not addressed.

For decades we, if not many other post frame designers and builders, have relied upon the bond strength between concrete and wood in designing column embedment to prevent uplift issues. More can be read about concrete to wood bond strength here: https://www.hansenpolebuildings.com/2013/04/pole-barn-post-in-concrete/.

I’ve expounded previously upon the use of nail on truss plates for assisting in uplift construction (https://www.hansenpolebuildings.com/2013/04/truss-plates-for-column-uplift/).

There truly is very little information available. Of all places, I did find some relevant information on the City of Hendersonville, Tennessee website (www.hvilletn.org):

Column uplift protection: Columns shall have uplift protection by one of the following methods:

1. Two 2x6x12 inch column uplift protection blocks attached to each side of the base of the column. The column uplift protection blocks must be placed horizontally, attached per Table 5 and comply with Section R317.

2. 12 inch high, concrete collar poured on top of footing around the post, with 2- #5×9 inch rebar placed through the post at 3 inches and 9 inches from bottom of post in opposite directions. The rebar ends shall be installed in accordance with ACI 332 for the specified distance in inches from contact with the soil.”

Table 5 mentioned above happens to be five 16d hot dipped galvanized nails into each block.

While I was researching for this article, I happened upon an example for preventing uplift in an all steel building. The building in this case was a 60 foot span and steel frames every 25 feet. In this case the design footing was eight feet square by 3’8” in depth!!

The all steel building is going to have footings which take nearly nine yards of concrete per bearing location!! This is near the capacity of a pre-mix concrete truck, per one end of each frame!

Getting back to the post frame building design solution, our engineers have determined reliance upon the concrete to wood bond strength only is not quite as conservative as they might like.

The solution – Hansen Pole Buildings, LLC engineered post frame buildings now have added the nail on uplift plate tot the roof supporting columns to tie into the concrete column encasement.

The investment is minimal and it does afford some added insurance of success in preventing uplift.

R-50 Insulation?

DEAR POLE BARN GURU: Did I read on this web page that there is a installation product that is one inch thick with a R rating of R-50? DELLA in DALLAS

DEAR DELLA: Unless I am mistaken, I believe your question is about insulation, rather than installation.

Yes, there is such a product. Here is the link to the article: https://www.hansenpolebuildings.com/2016/11/one-inch-insulation-r-50/

My guess is it may be on the expensive side, but if it works, it could be quite the trick. I am in the process now of getting a quote with the idea of using it between the framing and steel when I reroof my house near Spokane, Washington.

DEAR POLE BARN GURU: What should I pay for metal roofing labor costs? JUSTIN in GARLAND

DEAR JUSTIN: In the case of most structural construction on low rise buildings, the cost of labor is typically equal to about 1/2 of the cost of the materials. Obviously steep slopes, multiple hips and valleys, pitch changes (basically more complex roofs) will add to the cost.

DEAR POLE BARN GURU: The detail for setting posts shows 8” concrete under the posts and up 18” on the posts.

Can we pour the bottom 8” of concrete in the caissons, let it set overnight and then set the posts on

the 8” and pour the 18” of concrete ? One of the videos shows doing it this way. JIM in WINDSOR

DEAR JIM: While I am unaware of any video Hansen Pole Buildings has produced which shows a two stage pour, it can certainly be done. I usually try to avoid it just for the fact I am frugal and do not like to pay the short haul charges from the premix company. By pouring it all at one time, you can also speed up the construction process by a day, as you will not be waiting for two sets of concrete cures.

Concrete Considerations from the PBG!

DEAR POLE BARN GURU: Is concrete included in price? TRACEY in SUMTER

DEAR TRACEY: No, we do not include concrete in the price and here is why:

Most familiar, as well as most available is the Sakrete® general purpose High Strength Concrete Mix. When mixed per the manufacturer’s instructions, this mix affords a compressive strength of 4,000 psi (pounds per square inch) at 28 days.

The instructions are: Empty the contents into a mortar box, wheelbarrow, or mechanical mixer. When mixing by hand, form a crater for adding water.  Add water a little at a time.  Avoid a soupy mix.  Excess water reduces strength and durability and can cause cracking. A 60 lb. bag should be mixed with three quarts of water, an 80 lb. bag four quarts.

Now the realities of using bagged concrete for post frame building footings….

treated postIt is not unusual to have concrete encasements of 24 inches or larger in diameter and 18 inches or more in depth, in order to prevent building settling and uplift issues. One hole this size would take 4.71 cubic feet, or about 700 lbs. of concrete! Even a very small building with 18 inches of diameter and depth takes 2.65 cubic feet or about 400 lbs. of concrete.

With either 60 or 80 lb. bags, it is going to take a lot of bags! An average building could easily have 20 posts, and if looking at 700 lbs. of concrete per post, we are talking about 7 TONS of concrete (3-1/2 yards).

Ignoring the huge number of bags involved, there are some other realities.

Ever looked at the pallets of readi-mix bags at the lumberyard? Take a peek, next time. Notice how many of them are broken or leaking.

Due to weight, it may very well mean another delivery and another delivery charge. Trucks do not run for free.

Bags can (and will) break when being handled during delivery, unloading and being moved around the jobsite. It is going to happen, just plan on it.

From experience, lots of projects are not begun immediately after delivery. It is not unusual for delays of weeks, or even months before actual construction begins. Improperly stored, bags can get wet or absorb moisture and become solid before time for use. This equals a total waste of money, other than the chunks of concrete make for solid backfill.

Then there are the builders who insist upon throwing the entire bag (usually including the bag) into the hole. Their idea is ground water will cause the readi-mix to harden. Why does this not resemble the manufacturer’s instructions?

Readi-mix must be mixed thoroughly and evenly. How does mixing over 200- 60 lb. bags of Sackrete® by hand sound? Add too much water (three quarts exactly per 60 lb. sack) and the strength is reduced.

Use too much? As holes are always perfectly round (not), it is going to happen.

Save time, effort and money. Often all three can be saved by having the local pre-mix concrete company deliver concrete for holes (even if a “short load” fee is charged), as opposed to mixing on site.

DEAR POLE BARN GURU: I am building a 36 x 40 pole barn and I’m on a grade that drops approximately 4′ over the span of the building footprint. A home builder friend, a structural engineer, and my concrete guy have recommended traditional foundation with wet set permacolumns, but the builder I’ve contracted with wants to set columns on footers 3′ to 5′ in the ground and not use the permacolumns. The pole barn builder doesn’t think I need a retaining wall and should just have an excavator level what i need with a slope off the back. Seems a retaining wall in the back is better, which my concrete guy will pour, but still recommends foundation to eliminate frost heave. Use for building is car storage and shop with a lift.
Thank you in advance for your time and help. CHRIS in ST. LOUIS

DEAR CHRIS: This reminds me of a joke I once heard – a home builder friend, a structural engineer and a concrete guy enter a bar…….

Oops, kind of off track!

Some of the answer is going to depend upon what you want your yard to look like.

In any case – the actual pad of the building is going to need to be properly compacted (emphasis on proper) so those costs will be fairly even in any case. You’ll want to be reading about proper site preparation and compaction here (it is lengthy): https://www.hansenpolebuildings.com/2011/11/site-preparation/

What might appear to be the least expensive would be to just order columns long enough to get the required embedment depth as shown on the engineered plans, then fill afterwards, sloping away from the building. In order to keep the fill from sloughing off, it will probably result in a slope next to your building which will stretch out as far as 20 feet. You could easily invest in several hundred yards of fill!! If you can live with the look, might be the answer.

Building on top of a foundation – this is going to be the most expensive and certainly not the choice I would probably be making. It is also going to be tougher to build upon, due to the height of the walls plus the foundation.

Which leaves – build a retaining wall. I like this idea. Columns do not have to be longer (as long as fill is properly compacted).

By the way – there is no reason for ANY of these versions to frost heave as long as the site has been properly prepared. Read more about how to avoid frost heave issues here: https://www.hansenpolebuildings.com/2011/10/preventing_frost_heaves_in_pole_building_construction/

DEAR POLE BARN GURU: How much is the drip stop application for labor/material? Usually it comes already attached to the metal paneling. Do you figure it by square feet? JOSH in MANKATO

DEAR JOSH: For materials you are going to be looking somewhere in the neighborhood of 53 cents per square foot of roof surface. As a builder, if you are anywhere it is typically windy, I am going to give you a decent discount on my labor for having invested in it, because I don’t have to fight rolls of insulation flapping in the breeze.

 

Cost Savings of a Crawlspace vs a Slab!

DEAR POLE BARN GURU: I am building a pole barn 50 foot clear span wide, and 70 foot long, 16 foot to the eve. I am using 4×4 metal uprights on 20 foot spans, red iron purlins and stringers, and 4×4 metal welded all around the top. I am using conventional wood trusses engineered for my area on four foot centers. My question: Are the 4×4 square tubing uprights on 20 foot centers, with welded 4×4 square tubing around the top for the top plate heavy enough for this large of a building? Thanks, FLOYD in KIM

DEAR FLOYD: You asked for my honest opinion – here it is. I wouldn’t stand under or near your building as proposed in a wind or snow storm. With a 30 psf (pounds per square foot) roof snow load and a 100 mph design wind speed under the 2009 IBC (International Building Code) you are talking about some significant loads to be dealt with.

My best recommendation is to spend the money to have your proposed design reviewed by a RDP (registered design professional – engineer or architect) who can make the necessary revisions so you can end up with a building which will actually stand up under the imposed loads.

 

DEAR POLE BARN GURU: Read the article on crawl space verses slab. Is there any pictorial drawing showing a pole barn construction with a crawl space so I can better understand the pole installation? I assume it’s the same as ground level for a slab, but only 4” lower for the crawl space. Still would like to visually see drawing to fully understand. It is my plan to do most of the construction, but one thing I won’t do is concrete work and the price of concrete installed is expensive. At least a wood sub-floor I can handle, not to mention it makes it easier to run electrical, ducting and piping. DOUG in KIOWA

DEAR DOUG: I am with you when it comes to concrete work – I just won’t go there if I can at all help it!

imagesCrawl spaces for post frame buildings are most normally elevated above grade. The IBC (International Building Code) requires any not pressure preservative treated beams in a crawl space to be at least 12 inches above the underlying soil, and joists to be 18 inches above.

Think of the raised wood floor being created as a “loft” floor, with the beams attached to the columns and joists running between the beams. The difference being this loft floor is usually going to be somewhere 18 to 36 inches above grade (most people prefer their crawl spaces to be tall enough to actually allow easy access for running utilities).

 

DEAR POLE BARN GURU: How much for 12 x trusses that are 24′ with 4/12 or 6/12 pitch? Thank you DUNCAN in JOHNSTOWN

DEAR DUNCAN: Although we are not manufacturers or resellers of just trusses, I can give you some guidance as to information which will be needed in order for you to get a correct price.

The easiest thing will be to get a copy of your engineered building plans into the hands of the local truss providers. The plans will have the information required to give you an accurate price for the trusses, as well as insuring they will be designed to meet the loading conditions necessary for your particular building, at your site.

These items will include jobsite address, Roof Exposure Factor (to the wind, also known as Ce), the ground snow load (Pg), the sloped roof factor (Cs), the thermal factor (Ct) as well as the Importance factor (I). The type of roof materials being used as well as if there is a ceiling or not will also play into the end truss design. If your local Building Department has a minimum roof snow load requirement, this needs to be passed along as well.

With all of the above in hand, the truss designer can plug the variables into the computer program which does truss design and derive a price for your truss package.

The above is merely a broad overview, to delve deeper, it would behoove you to read the article I penned for Structural Building Components magazine: https://www.hansenpolebuildings.com/mike-the-pole-barn-guru-profile/it-isnt-your-grandpas-barn/

 

 

Hurl Your…Concrete Cookies

I know none of us has ever experienced this condition, but we all know of someone who has had the hurling issue, often after a period of personal discussion with some of the friends of George Thorogood.

In this instance, I’m not thinking either of the example above, or the tasty oatmeal raisin cookies my grandma made for us when we were kids. I am making specific reference to the pre-cast chunks of concrete usually four to six inches in thickness and 12 to 18 inches in diameter which are sold or provided for footings in pole buildings.

The basic concept is to throw concrete cookies in the bottom of the augered holes and place the building columns directly upon them. The general idea is for the cookies to support the weight of the building, to prevent settling.

My recommendation – RUN, DO NOT WALK, away from this as a design solution.

Why?

They are a failure looking for a place to happen.

Let’s look at what a footing is supposed to do. The dead weight of the building PLUS all imposed live loads must be distributed to the soils beneath the building. Sounds pretty simple, eh?

Concrete Cookie

Concrete Cookie

To begin with, the International Building Codes require concrete footings to be a minimum of six inches in thickness. This eliminates immediately any concrtete cookies which are less than this thickness (most of them).

Examine a fairly small example – a 30’ wide building with columns spaced every eight feet. The actual weight of the building (dead load) will vary greatly depending upon the materials used. Steel roofing and siding will be lighter than shingles and wood sidings. For the sake of this example, we will use a fairly light 10 psf (pounds per square foot) building weight. The Code specifies a minimum roof live load of 20 psf. This means each footing must carry the weight of one-half of the width (15 feet) times the column spacing (8 feet) times 30 psf. Doing the math, 3600 pounds.

In many parts of the country soil bearing pressures are as little as 1500 or even 1000 psf. Basically – the easier it is to dig, the lower the capacity of the soil to support a vertical load.

For every foot of depth below grade, the soil capacity is increased by 20%. Other than with 1000 psf soils, for every foot of width over one foot, the capacity also gets a 20% increase.

With 1500 psf soil, and the bottom of the footing four feet below grade, a 12 inch footing will support 2700 pounds per square foot.

A 12 inch diameter footing covers 0.785 square feet, a 16 inch 1.4, 18 inch 1.77, 24 inch 3.14.

The 16 inch footing would support exactly the 3600 pounds from the example above. However – lots of places in the country have snow loads (which the footings must support) and many buildings are wider than 30 feet, or have columns placed over eight feet apart.

Trying a 40 foot span, with a 40 psf roof snow load, same eight foot column spacing, would mean resisting an 8000 pound load! With 1500 psf soils, even a two foot diameter footing would be inadequate.

In most cases, the use of concrete cookies as footing pads proves to be both inadequate and a waste of good money. To insure a building won’t settle, (from inadequate footings), look for a plan produced by a registered design professional who is proficient in post frame building design. He/She will have the history and training to design your building to withstand the loads…which begins with the foundation.