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Concrete Slabs on Grade for Cold Climates

Concrete Slabs on Grade for Cold Climates

My lovely bride and I have a shouse (shop/house) in Northeast South Dakota, where it can tend to get chilly in Winter. Reader TERRI in DULUTH is in a similar situation and writes:

“What type of slab for cold climates do you recommend?”

Well Terri, thank you for your patience in awaiting a response, your email address was not included with your question, so I was unable to message you back as quickly as I would have liked.

PLEASE – If writing an “Ask the Pole Barn Guru” question include your email address.

Injecting some humor (sadly, I have to point it out as not everyone gets it) – I would recommend a concrete slab.

Before diving into this subject – accept one fact, concrete slabs will crack. If you are expecting otherwise, you are setting yourself up for disappointment.

First key to a successful slab is excellent site preparation: https://www.hansenpolebuildings.com/2017/02/building-site-preparation/

Second – insulate your slab’s perimeter. 2021’s International Energy Conservation Code (IECC) provides guidance to meet energy code requirements for every county within our country. Begin by looking up your Climate Zone: https://codes.iccsafe.org/content/IECC2021P1/chapter-3-re-general-requirements

I will cheat and tell you Duluth (St. Louis County) is climate Zone 7.

Scroll down to Table R402.1.3 to find Insulation Minimum R-Values.

In Climate Zone 7 your slab perimeter must be insulated to R-10 and be four feet in depth. 

Weirdly enough, Minnesota’s Building Code only requires footings to be at 60 inches of depth in your area (https://www.revisor.mn.gov/rules/pdf/1303.1600/2015-01-23%2012:37:31+00:00). 

Although actual frost depth in your area is more like 80” in depth:

I would probably look at augering holes no less than 72 inches in depth, using a bottom collar of 18 to 24 inches (per your engineered building plans). This would allow you to trench between building columns and install R-10 rigid insulation along your building’s perimeter to a depth of four feet.

If you are going to do radiant in-floor heating you should be placing R-10 beneath your slab and on top of a vapor barrier of no less than 6 mil visqueen (I prefer 15 mil thickness to reduce chances of perforations during pouring).

This entry was posted in Pole Barn Homes, Pole Barn holes, Pole Barn Questions, Pole Barn Design, Post Frame Home, Pole Barn Planning, Shouse, Concrete, Footings, Professional Engineer and tagged , , , , , , , on by .

Barndominium Building on Solid Ground

For many, a new barndominium is looked upon as being a ‘forever’ home. This is an opportunity to have a floor plan custom crafted to meet all sorts of family wants and needs – whether it is a huge country kitchen or shop space big enough to house a fleet of classic vehicles.

It is yours.

It is YOUR hard earned dollars going to pay for this lovely new home.

While I encourage everyone who can to at least act as their own General Contractor (https://www.hansenpolebuildings.com/2020/02/does-my-barndominium-need-a-turn-key-general-contractor/), not everyone feels confident in doing this. In some instances lenders require a General Contractor’s involvement. For others, their new barndominium and their current home and careers are geographically not close enough to allow for this to occur.

Scary things can happen when turnkey General Contractors are left to their own devices. I have penned previously (okay hunt-and-pecked) on how to avoid General Contractor challenges (https://www.hansenpolebuildings.com/2019/11/a-contractor-for-your-new-barndominium/).
Crucial to long term success with your new barndominium is having a solid base to build upon. Those doing work DIY have an advantage – you get to supervise (or do) site preparation and any needed compaction.

drywall crackHaving a barndominium built? You may anticipate a few things going wrong, but you’d expect your builder to erect your house on solid ground, right? Don’t be so sure.
Population growth and urban sprawl mean there’s not much residential land left in many areas. “What’s left is not very good,” says Daniel G. Knowler, a senior engagement manager at Navigant Consulting, specializing in construction disputes. A lot of homes are being built on expansive soil — it swells when it rains — without adequate safeguards.

One family moved into their new home in Highlands Ranch, Colorado, and long cracks started showing up in walls, then their porch started pulling away from their house. After badgering his builder for a soils report, this homeowner learned their lot was a hot spot for potential swell! Eventually a court found for these homeowners and ordered restitution from said builder.

(for extended reading on barndominiums on expansive soils please see: https://www.hansenpolebuildings.com/2020/07/barndominium-on-expansive-soils/)
Problems besides swelling soil can occur. In Laguna Niguel, California four hillside homes built on an ancient landslide site toppled after unstable soil gave way. Besides these four homes collapsing, they landed on top of other dwellings below – destroying them!

Do not assume a turnkey General Contractor will make all potential problems go away, sadly they can cause more than they solve.

This entry was posted in Pole Barn Homes, Post Frame Home, Barndominium, Shouse, Pole Barn Design, Pole Barn Planning, Building Contractor and tagged , , , , , , , on by .

How to Re-level a Garage

Auntie Em, Auntie Em My Garage Has Lifted 

Well, it wasn’t from a twister and this article has nothing actually to do with Auntie Em or actress Clara Blandick who played Auntie Em in 1939’s film classic The Wizard of Oz. For trivia buffs, Blandick also played a part in 1937’s original A Star Is Born.

Reader GEORGE in LAGRANGE might be wishing a twister had hit his garage, so insurance would pay for a replacement. George writes:

“Due to the freezing and thawing cycle my pole garage has lifted about 7 inches since it was built 12 years ago. You can now see the outside grass from inside the garage. And it has not lifted evenly so the garage is unlevel.”

George’s post frame garage has some challenges, none of them ones with an easy fix. How did his garage get this way? There are three possible major contributors to this garage’s current situation. These would include:

Inadequate site preparation

At a minimum, site preparation includes:
· Remove all sod and vegetation.
· For ideal site preparation, remove topsoil and stockpile for later use in finish grading. In frost prone areas, remove any clays or silty soil
from within future building “footprint”.
· Replace subsoil removed from around building with granulated fill to help drain subsurface water from building.
· Distribute all fill, large debris free (no pit run), uniformly around site in layers no deeper than six inches.
· Compact each layer to a minimum 90% of a Modified Proctor Density before next layer is added. Usually, adequate compaction takes more than driving over fill with a dump truck, or
earth moving equipment.

For more details on proper site preparation please read: https://www.hansenpolebuildings.com/2011/11/site-preparation/

Column Depth

Bottom of column encasement needs to be below frost line. This is a no-brainer.

Water

Read more about what causes frost heaving here: http://www.hansenpolebuildings.com/2011/10/pole-building-structure-what-causes-frost-heaves/.

There is going to be no easy or inexpensive fix to George’s situation. An investment into a geotechnical engineer who could provide a thorough site evaluation along with solutions might be money well spent.


Building could be brought back to level by excavating at each raised column to well below frost depth. Cut off columns at base of splash plank (while supporting building from falling), then remove embedded portion of column. Place an appropriately sized sonotube in excavation with top of tube at grade. Pour premix concrete into tube and place a wet set Sturdi Wall bracket – expertly placed to receive upper portion of column. https://www.hansenpolebuildings.com/2013/11/sonotube/

If all of this sounds daunting (it would be to me), a consideration could be demolition and start over from scratch.

This entry was posted in Pole Barn Questions, Pole Barn Design, Pole Building How To Guides, Pole Barn Structure and tagged , , , , , , , , on by .

North Carolina Students Learn Post Frame Construction

North Carolina College Students Learn Post Frame Construction

The following article by Dan Grubb appeared first in the December 5, 2018 Sampson Independent

“Sometimes the building blocks to success look more like beams than blocks. Students at Sampson Community College’s Building and Construction program know this first hand as work continues on a facility the class is building on campus.

“Every day that we can put equipment into the hands of these students and let them go out and build things, the closer we are to them seeing a successful career, “says Dustin Hatcher, Building and Construction Instructor at SCC. “We allow the students to work from top to bottom, start to finish—the entire project. This building will be used as a storage unit for the college’s Maintenance department. This is something they can go to an employer with and say ‘Hey, I’ve done this!’”

This week, students installed engineered wood structural beams onto posts that will be supporting the roof trusses of the building. They are learning how to set up and move scaffolding platforms and accurately measure, mark, then cut the beams with saws and fasten beams in place with nail guns. This provides experience working from elevated platforms and the use of some of the most common tools used in framing carpentry.

The Building Construction Technology curriculum at the college is designed to prepare individuals to apply technical knowledge and skills to the fields of architecture, construction, construction management, and other associated professions. Graduates will qualify for entry-level jobs in architectural, engineering, construction and trades professions as well as positions in industry and government. The course offers instruction in construction equipment and safety; site preparation and layout; construction estimating; print reading; building codes; framing; masonry; heating, ventilation, and air conditioning; electrical and mechanical systems; interior and exterior finishing; and plumbing.

Employment of these types of positions are projected to grow 12 percent from now until 2026, faster than the average for all occupations.”

Mike the Pole Barn Guru adds:

Although this particular project does not happen to be a Hansen Pole Building, we do work closely with interested high schools, colleges and universities in support of Building and Construction or Vocational Education programs. For more information on how you and your school can participate: https://www.hansenpolebuildings.com/2016/01/high-school-classes/.

 

This entry was posted in Lumber, Pole Barn Design, Building Department, Constructing a Pole Building, Pole Barn Structure and tagged , , , , , on by .

Help! My Pole Barn Has Frost Heave

Help! My Pole Barn Has Frost Heave

Reader DAVID in MINNESOTA writes:

“I looked through many pages of your blog and found nothing yet that deals with my frost heave problem.

Bought lake property 8 years ago that had a 24 X 24 pole shed that was 5 years old. It has concrete floor with concrete on 3 sides of each 6 X 6 except pole by walk-in door which has concrete on all 4 sides. Poles every 8 feet except front (west) side which has 16′ garage door and walk-in door.

All poles are moving up except maybe corner pole in SE corner. They vary in movement from 1-5 inches. I dug down in one corner to see how deep the poles are in the ground and it was 56 down to what feels like a concrete pad at the bottom of the hole. The building is located is central Minnesota in a lakes region with sandy subsoil.

I am considering attaching 2 X 12s to the inside of the poles at the level they were initially at the top of the floor. Then cutting off the poles to lower the building and attaching some heavy angle iron to the 2 X 12s and the floor.

Another consideration is to try to jack up each pole so they are all level again and attach the angle irons to the poles and the floor and then deal with the doors.

The floor has not sunk (the electric service cable coming in pulled down on the breaker box and broke the main breaker) but the floor is in good condition.

Two of the poles would not be able to be dug down to the bottom as the septic tank is too close.

Your thoughts would be greatly appreciated.”

Mike the Pole Barn Guru writes:

In your property purchase you have inherited someone else’s lack of planning which has become your problem. The great majority of frost heave potential can initially be solved by proper site preparation – and your building is fairly obviously not on a properly prepared site.

Cutting off the poles and lowering the building is probably not going to be a fix and is going to add even more problems. You will now no longer have proper transfer of downward loads to the footing pads and to prevent settling would require any brackets to be able to spread the loads out over a large surface of your concrete slab – with the strong potential for your slab to be cracked by them. Provided you were able to adequately distribute the loads, you also have the issues of uplift and overturning to overcome and your probably four inch thick concrete floor is possibly not adequate to withstand any of these forces.

In all likelihood the answer probably lies in getting the water out from under your building – which may involve some sort of trenching around the perimeter. Your septic system being so close to your building is probably adding to the problem (this is part of why Planning and Building Departments require buildings to be set back from septic systems).

Obviously you are asking for some expert advice, which could save your building. Due to the factors involved in your particular site – I am going to recommend you hire a registered professional engineer who specializes in soils to come to your site and do a thorough analysis of the situation. He or she should be able to design a fix for your challenge – however (just a warning) the solution could be more expensive than the building is worth.

Sadly, it could be the best solution may be to properly prepare an adjacent site, take the building apart and reassemble it on the better location.

This entry was posted in Pole Barn holes, Pole Barn Questions, Pole Barn Design, Pole Building How To Guides, Pole Barn Structure, Concrete, Columns and tagged , , , , on by .

Setting Posts on Stands?

Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: Have you ever tried using stands under your posts before you pour. I like the concept brand “X” uses, just seems a little overly complicated. Thanks. SCOTT IN MACOMB

DEAR SCOTT: Without knowing who Brand “X” is, hard for me to comment on their methodology. I have not personally tried the use of stands, however I have written about them: https://www.hansenpolebuildings.com/blog/2014/05/one-pour-reinforcement-cage/.

This does seem like a costly method, when it is actually quite simple to just ‘float’ the posts in the holes: https://www.hansenpolebuildings.com/blog/2015/04/floating-poles/

Mike the Pole Barn Guru

DEAR POLE BARN GURU: Hi, I’m putting in a pole barn, and where it’s located is about two feet low from the driveway. This area gets a bit wet during rains, and I was wondering what would be the best solution to build up the area? I will be pouring a concrete pad eventually. Should I use a crushed gravel or something like a bank run dirt (processed fill with dirt and stone)? Thanks! MATT IN OSWEGO

DEAR MATT: Most certainly an excellent idea to raise up the site of your new pole building – the last thing you want to do is have it sit in a hole!

Rather than rehash a well-covered prior topic, you should read through the series of articles I wrote beginning with this one: https://www.hansenpolebuildings.com/blog/2011/11/site-preparation/

By inputting your “key word” in the search field on the blog page– you can read other articles on related subjects. I think you will find lots of useful information in past blogs.

Good Luck!   Mike the Pole Barn Guru

DEAR POLE BARN GURU: Hi. I’m building a 12 by 20 pole barn (gambrel roof). So far I just finished the trusses and I’m going to be setting the poles in few days. I’m following the instructions from a book building a shed from Joseph Truini. And I got extra plans from perfect barns company from same book.

My questions:

  • In the book they set the post or pole in one bag of concrete for each post for footing then they set the post and build the walls and after framing the wall they set the post.

Is this crazy to put walls before setting posts?

  • After they frame the walls the only add 1/2 bag of concrete to each post, is this enough?
  • I live in Edmonton, Canada where the winters are weeks of 20 (C) below so I need to make sure the structure is strong enough to last this extreme weather.

The frost line around here is more than 4 feet, I’m planning in digging as deep as I can get – maybe 8 or 10 feet. Do you think this is enough?

MARITZABEL IN EDMONTON

DEAR MARITZABEL: Based upon the information I have been able to find on the internet it sounds like the eight to 10 foot frost depth is probably correct. I do really question a footing made from only one bag of premix – footings should be six to eight inches thick at a minimum and even on a small building, probably at least 18 inches in diameter. Adding another ½ bag of concrete later, after walls are up, sounds like a waste of a ½ bag of premix.

I’d stand the columns in the holes, float them eight inches off the bottom of the hole and pour at least 18 inches of concrete in the bottom.

Without looking at the plans you are working from, I have no idea of how one could possibly frame walls before setting posts.

Mike the Pole Barn Guru

This entry was posted in Pole Barn Questions, Concrete, Columns and tagged , , , on by .

Building Site Preparation Part II: Soil Compaction

This is day two in several where I am discussing all kinds of issues with site preparation, mostly what to do with the…dirt.

So what actually is soil? Soil is formed in place or deposited by various forces of nature – such as glaciers, wind, lakes and rivers – residually or organically.  The important elements in soil compaction are soil type, soil moisture content and compaction effort required.

There are five principle reasons to compact soil: to increase load-bearing capacity, prevent soil settlement and frost damage, provide stability, reduce water seepage, swelling and contraction and reduce settling of soil.

The Leaning Tower of Pisa would have benefited from a soils engineer and a soil compaction test. The tower was in trouble before it was even finished. According to www.buzzle.com after the tower reached its third floor construction in 1178, they had to stop the work as the structure started to sink in the ground. This was due to weak and unstable soil where the foundation was being constructed. The work was halted for almost 90 years after that. The halt in the construction gave time for the soil to settle; otherwise the tower would’ve definitely collapsed. As there was a tilt in the building, the engineers had to build the next 4 floors, with one side taller than the other. Thus it manipulated the tower to lean in the opposite direction.

Soil can be compacted by vibration, impact, kneading or pressure. These different compaction efforts can be accomplished by the main types of compaction force, static or vibratory.

Static force is simply the deadweight of the machine, applying downward force on the soil surface, compressing the soil particles.  The only way to change the effective compaction force is by adding or subtracting the weight of the machine.  Static compaction is confined to upper soil layers and is limited to any appreciable depth.  Kneading and pressure are two examples of static compaction.

Vibratory force uses a mechanism, usually engine-driven, to create a downward force in addition to the machine’s static weight.  The vibrating mechanism is usually a rotating eccentric weight or piston/spring combination (in rammers).  The compactors deliver a rapid sequence of blows (impacts) to the surface, thereby affecting the top layers as well as deeper layers.  Vibration moves through the material, setting particles in motion and moving them closer together for the highest density possible.  Based on the materials being compacted, a certain amount of force must be used to overcome the cohesive nature of particular particles.

Poor, improper or no compaction can result in concrete slab cracks or frost heaves, foundation erosion and/or building settling. Proper compaction can ensure a longer structural life.

Every soil type behaves differently with respect to maximum density and optimum moisture.  Therefore, each soil type has its own unique requirements and controls both in the field and for testing purposes.  Soil types are commonly classified by grain size, determined by passing the soil through a series of sieves to screen or separate the different grain sizes. Soils found in nature are almost always a combination of soil types.  A well-graded soil consists of a wide range of particle sizes with the smaller particles filling voids between larger particles.  The result is a dense structure which lends itself well to compaction.  A soil’s makeup determines the best compaction method to use. There are three basic soil groups: cohesive, granular and organic. Organic soils are not suitable for compaction.

Cohesive soils, such as clays or silts have the smallest particles. Cohesive soils are dense and tightly bound together by molecular attraction.  They are plastic when wet and can be molded, but become very hard when dry.  Cohesive soils feel smooth and greasy when rubbed between fingers. Clay soils are less than ideal to construct your new pole building upon and should be removed and replaced.

Granular soils range in particle size from .003″ to .08″ (sand) and .08″ to 1.0″ (fine to medium gravel).  Granular soils are known for their water-draining properties. Sand and gravel obtain maximum density in either a fully dry or saturated state.  Granular soils feel gritty when rubbed between fingers. When water and granular soils are shaken in the palm of your hand, they will mix, when shaking stops, they will separate. When dry, a soil sample will crumble.

Gravel and sand can be compacted either by vibration (using a vibrating plate compactor, vibrating roller or vibrating sheepsfoot) or kneading with pressure (using a scraper, rubber tired roller, loader or grid roller). Both are good to excellent in terms of foundation support and as a subgrade. They are easy to compact and are not expansive (expansive soils tend to be prone to frost heave issues).

Whew!  That’s a mouthful and then some in talking about compaction.  Too bad the contractors working on the Leaning Tower of Pisa didn’t know all of this!  The good news is, in 1990 efforts were made to correct the angle from 5.5 degrees to 3.99 degrees, and engineers have determined it stopped sinking since about 2008 and will continue to be stable for another 200 plus years.  If I ever get the chance to see it (my bride is determined we will!), I’ll be sure to have my picture taken outside…with my feet planted firmly on the ground

This entry was posted in Pole Barn Planning, Building Department and tagged , , on by .
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