Tag Archives: crawl space

Avoid Being Driven Crazy With Barndominium Questions Part I

Avoiding Being Driven Crazy With Barndominium Questions Part I

Loyal reader and client GREG in KENTWOOD is planning his new post frame barndominium home and has questions no one else will answer. Mike’s answers are in italics.

Mike,

Good morning, I hope all is well with you.  

 I have some questions that I would like to understand and it is driving me crazy, because no one other than Hansen Pole Building, it seems will answer my questions and return my calls.  Most the crazy part is about the slab. I find cement workers are not great communicators.  I am 56, a mechanical engineer, have renovated several houses from the studs up, I can do plumbing without butt crack showing, I raced stock cars for 10 years, I tell you this, because I know how to build stuff and am not afraid of hard work. My job requires a detailed list of Bill of Materials, precision drills and reamers and very detailed processes to make fuel injection parts, ABS brake parts and other.  I hope you can help out, as I am ignorant about some simple facts that are driving me crazy.

Mike: We believe good communication is essential to successful completion of most any building. You will find we strive towards written communications in order to minimize (or eliminate) possible miscommunication of important facts and details).

I also would like to say Brenner is doing a fine job.

Mike: Brenner has a passion for post frame buildings and he is not at all afraid to reach out to higher authorities for answers to complex structural questions.

Due to your great level of communication, you so far are my #1 choice to partner with on my new house.  I also would be willing to visit you in MN if you have/think I could see examples of my questions first hand.  

Statements from details I learned at Code Meeting:

  • In Michigan, in my county I need to have a 2’ foam, below grade, with R10 barrier, around the full foundation or slab perimeter. 
  • So my building code staff recommends a Rat Wall 2’ below grade, or a crawl space with footers, or a slab with a wooden wall built to hold the 2’ foam below grade.
  • I don’t really have a problem with the Rat Wall, but it certainly will add more cost to cement.

My questions on this topic are:

    • If using a Rat Wall, it seems like the 6” * 6” poles will then be encapsulated in cement for about 2.5’ at minimum.  I thought the poles were not supposed to be in cement as it causes probably more decay than dirt.
      Mike: Concrete does not cause premature decay of properly pressure
      preservative treated columns.
    • What are your thoughts?
      Mike:
      Personally I would build over a crawl space because my knees are far happier living on wood than concrete.
    • What would you recommend for the 2’ below grade issue regarding the slab foundation?  Mike: With a slab on grade, you can use rigid perimeter insulation without a need for a ‘rat wall’ or wood foundation wall. It can be held in place by backfill on each side. It can be placed running from below base trim on exterior of splash plank, or on inside of splash plank. If on inside of splash plank, it eliminates having to protect it from possible UV degradation.

On attachment pictures in the middle pages show where the 6” X 6” poles go and spacing, listed are my questions:

I am concerned with spacing of 12’ and 14’ of the 6” X 6” posts.  (I’m sure the loading is OK, within code, but see below)
Mike:
Actually with your 21 foot eave height and Exposure C for wind 6×6 columns will not engineer out. Your building will have glulaminated columns manufactured out of high strength 2×6 or 2×8 depending upon location.

    • One concern is getting wood in today’s supply chain that are straight enough for the girt boards and purlins at 12’ and 14’, should I be concerned? ( I can’t get straight 2” X 4” at 8’ for the walls I have built in last year alone.) Mike: Lumber is obviously organic and we can no longer cut down those old growth trees where one might be able to get straight grained, narrow growth ringed lumber with few or no defects and very little warp, twist or cup. One beauty of steel roofing and siding is it hides a plethora of framing imperfections (like warp), due to high ribs of steel siding.

When using double trusses, at all locations, why not just go to 8’ centers on the poles?   I know it is more 6” X 6” poles, but really is not anymore trusses and may help get straighter girt and purlin boards. 
Mike: Wider spaced columns allow for more flexibility in location of doors and windows and an added advantage of not having to dig as many holes. If you were thinking of using a single truss every eight feet, rather than a double truss every 12, I would discourage it. Double trusses allow for true load sharing and eliminate any possibility of a single truss having a weak point, where under extreme loads (beyond design loads) it may fail and bring down your entire roof.

Come back tomorrow for Part II in Barndominium Questions!

Post Frame Home Zero Barrier Entry Over a Crawl Space

Post Frame Home Zero Barrier Entry Over a Crawl Space

Reader MARC in AUBURN writes:

“I am asking what might be an odd question, but I need to ask it to see if it is even an option.

Is it possible to build a post frame home with part of it having a concrete floor (garage area) and the other part be built on a raised wood joist subfloor spring that I have a 4 foot crawl. The trick is, I want zero barrier entry so the sub floor and the garage floor would need to be level. Same with porches, etc.  is this doable without building an actual foundation wall around the home section?  I want to avoid traditional foundations and want to rely on the superior properties of a properly engineered and constructed post frame building. Am I better off just going all slab without a crawl?  

Thank you!”

Not an odd question at all and yes it is an option. I (and my knees) personally prefer to live on wood floors, rather than concrete. Our household also relates to zero barrier entry as my lovely bride Judy is a paraplegic confined to a wheelchair.

We can design your living space using permanent wood foundation walls between roof supporting pressure preservative treated columns.

Treated wood foundations are load-bearing, pressure-treated wood framed walls, used below grade to support light frame construction. Treated wood foundations are commonly called Permanent Wood Foundations or All-Weather Wood Foundations. Since being developed in the 1960s, this unique building system has proven to be a durable building system in thousands of physical applications. Treated wood foundations have undergone extensive research, analysis, and testing by several highly respected building construction industry organizations. They have been approved for use by model building codes, federal agencies, and by lending, warranty and insurance institutions. A treated wood foundation, when installed, waterproofed, and drained properly, and used in conjunction with other waterproof materials, is a viable alternative to poured concrete or concrete block foundations. When I added onto my home near Spokane, Washington 30 years ago, I utilized pressure preservative treated wood as a foundation around an irregular crawl space supporting two floors and cantilevered decks above. It has performed admirably, even in a severe lakefront environment.

Treated wood foundations are built on most types of soils (Group I – III), with an exception of unsatisfactory soils (Group IV) as defined by the U.S. Department of Agriculture. Group IV soils typically have over 40% clay, less than 50% sand and may have a high shrink-swell potential. Similar to conventional foundation systems, sites should be cleared of organic material and top soil prior to work onset. Crawl space is then excavated, and a footing is placed on undisturbed soil below frost line. Footings under a treated wood foundation wall can be made of poured concrete or a wood footing plate on top of granular fill. In my case, I used a poured concrete footing, however in your instance, since vertically carried loads would be minimal, gravel should prove more than sufficient. as footing size is engineered based on foundation wall loads. Adequate, unobstructed drainage around a treated wood foundation is achieved by having continuous granular fill on building sides and underneath structure. Granular material can be up to 1/2 inch crushed stone, 3/4 inch gravel or 1/16 inch sand depending on where it is intended to be used. All granular material should be clean and free of silt, clay and organic material, and be covered with a 6-mil polyethylene sheeting. Sump pumps, perimeter drains, and dry wells may be used under your crawl space floor and around the exterior to promote drainage.  Storm water control including gutters, downspouts, splash blocks and drainpipes, in addition to a properly sloped finish grade, is also important to direct water away from the structure. 

Materials used to construct treated wood foundations include: plywood, preservative treated lumber, fasteners, termite protection (where appropriate), a moisture barrier, sealing, and insulation. All framing lumber below grade in a treated wood foundation is required to be pressure treated with preservatives in accordance with the American Wood Preservers’ Association (AWPA) Standard C22, “Lumber and Plywood for Permanent Wood Foundations – Preservative Treatment by Pressure Processes.” An important consideration when building a treated wood foundation is the metal used in the fasteners. Due to the high levels of copper in wood preservatives, fasteners are required to be a corrosion-resistant. Type 304 or 316 stainless steel nails are recommended.

An essential part of a treated wood foundation system is moisture and termite protection. In addition to a 6-mil polyethylene sheet wrapped around exterior plywood sheathing, all sheathing joints must be caulked with a high-performance acrylic latex or polyurethane caulk. Preservative treated wood eliminates termites from crawl space framing, because termites cannot penetrate it; however, additional steps should be taken to protect untreated floors above.

Several advantages make treated wood foundations an attractive option. Construction of a treated wood foundation is simple to erect, in comparison to concrete foundations. Treated wood foundations also offer advantages over concrete foundations such as an ability to install insulation between studs, affording a higher R-Value in comparison to uninsulated concrete foundation walls, leading to greater energy efficiency.

A Dog Trot Post Frame Home

A Dog Trot Post Frame Home

Welcome back!

If you missed yesterday’s installment, you will want to flip a page back, otherwise this will not make sense!

Thank you Jim for your kind words – so much to write about and so little time 🙂 I do endeavor to provide to anyone who wants to read, best possible and researched information. I also tell it like it is, rather than just giving answers you want to hear.

For those who may read this later, a ‘dog trot’ style building historically has two individual sections, connected by a breezeway. Dog trot homes are typically raised off the ground and have a wide front porch along an entire length. Normally one section will have ‘day functions’ (cooking, dining, living) and its counterpart will have ‘night functions’ (sleeping, bathrooms). I would encourage you to consider putting up this building shell in its entirety at one time as there will be economies to be derived in only one set of deliveries as well as labor savings in not having to tear anything apart in order to conjoin first and second stages. You could certainly complete all inside finishes of each section independently.

Being able to pass a blower test is less a function of the structural system than it is of properly constructing a well-sealed building envelope. It is also not yet a nationwide mandate – Florida just happens to be one of a handful of states where it is required. By using two inches of closed cell spray foam insulation on all surfaces and properly installing all doors and windows you should have no issues with passing a blower test. Our third-party engineers do a thorough check on every member and connection to ensure all are adequately designed to resist the imposed loads – including column uplift. Screw tie downs will not be required in order to resist columns uplifting (at least not by our engineers). Raised wood floors (over crawl spaces) are becoming more and more popular as people are realizing they are available and do not like the idea of living upon concrete floors https://www.hansenpolebuildings.com/2019/03/slab-on-grade-or-crawl-space/ . One of our recently retired Building Designers, Rick Carr, has recently built a hunting cabin for himself over a crawl space https://www.hansenpolebuildings.com/2020/06/fishing-cabin-insulation/.

One of our Building Designers will be reaching out to you for further discussions. I would also recommend you get into our queue for getting floor plans and elevation drawings generated http://www.hansenpolebuildings.com/post-frame-floor-plans/?fbclid=IwAR2ta5IFSxrltv5eAyBVmg-JUsoPfy9hbWtP86svOTPfG1q5pGmfhA7yd5Q.

Slab or Crawl, Insulation, and Building by a Leach Field

This Monday the Pole Barn Guru answers reader questions about building on a slab or with a crawl space, insulation for a shop, and if a person is able to build near a leach field.

DEAR POLE BARN GURU: I appreciate the building technology used when building a residential pole barn. I am not yet convinced about a slab floor. Although radiant heat is a plus I have two concerns. 1st I’m not sure of the impact when walking on concrete and what is done about air conditioning the building. Have you seen pole framing on a stem wall crawl space deck. Thanks. JOHN in SUMMERSVILLE

DEAR JOHN: Although our own shouse has geothermal radiant floor heating and cooling (https://www.hansenpolebuildings.com/2016/12/modern-post-frame-buildings-geothermal/) I tend to agree with you about what surface I would like to live upon. If I had to stand on concrete for very long, my knees would be screaming at me. We have provided many post frame buildings built over crawl spaces, with most using embedded columns and attaching raised wood floor supports to them. This is far more cost effective than pouring a stemwall (we have had clients go this route as well). For extended reading please see https://www.hansenpolebuildings.com/2019/03/slab-on-grade-or-crawl-space/.

DEAR POLE BARN GURU: I’m working with Greg Lovell on a building design. Pole barn 30 x 48 x 10 will be walled of to two 24 X 30 shop areas.

My question is on insulation, I’ve read you recommend a ceiling and insulating above that with a vented ridge.

So… if this is not going to be a building I heat 24/7 and never cool. Can I get by with reflectix under the metal roofing and insulating between the purlins with unfaced insulation, if I’m only going to heat it when I’m in it during the winter (heat with a wood stove).

Your post says if I do it this way I need to construct an air gap between the purlins and the roofing material, given the above scenario do I need this air gap if I only heat it a few times a week during the day? Obviously if I do need the air gap the ceiling would be a better way to go. LEE in IDAHO FALLS

DEAR LEE: Code does require airflow above insulation from eave to ridge with this scenario. An option might be to use two inches of closed cell spray foam insulation applied directly to roof steel underside. This would eliminate a need for a Reflective Radiant Barrier as well as ventilation above it. Closed cell spray foam should run roughly two dollars per square foot of roof surface and provide about R-13.

Advantage of a ceiling with insulation blown in is you only heat area below ceiling. Should you or some future user decide to climate control, this would provide a big start.

 

DEAR POLE BARN GURU: Can you build a pole barn at the bottom of a leach field? TRACE in JAMUL

DEAR TRACE: Yes you can. Typically most jurisdictions require any non-full foundation buildings to be at least 10 feet from any leach line. Consult with your local Health Department for requirements for your jurisdiction.

 

 

 

 

Raised Floor Over Crawl Space, Engineered Plans, and a Pool House

This week the Pole Barn Guru answers questions about a raised floor over a crawl space, purchase of engineer sealed plans, and moisture issues in an above ground pool house.

DEAR POLE BARN GURU: Appreciate all the information on your website very awesome it’s a lot to take in we are thinking of building a pole barn home and we have one question we typically don’t like concrete floors. I joist, does anybody just frame out floor joist, has with a 3 in rat slab for crawl space? GARY

DEAR GARY: Thank you for your kind words.

I would rather not live on a concrete slab either. One of our retired Building Designers has been putting up a hunting cabin done exactly as you envision:

https://www.hansenpolebuildings.com/2019/03/development-of-my-cabin-plans/
https://www.hansenpolebuildings.com/2019/03/pole-barn-cabin-part-ii/

https://www.hansenpolebuildings.com/2019/04/my-pole-barn-cabin-part-iii/
https://www.hansenpolebuildings.com/2019/03/participating-in-ricks-post-frame-cabin-planning/

Engineer sealed pole barnDEAR POLE BARN GURU: Do you sell only engineered plans for your building? I am interested in PROJECT# 06-0602 but I do not want to buy a kit.

Thanks! MATT

DEAR MATT: Thank you very much for your interest. Our independent third-party engineers will only provide sealed plans for buildings where we are providing materials, as there is no other way they can guarantee materials as specified actually arrive at your building site. Some of these are manufactured specifically for Hansen Pole Buildings, so there is no other method to acquire them. Frankly, our massive buying power allows us to acquire components at far better prices than you will be able to find and our low overhead and narrow profit margins allow for us to be extremely competitive, even with lesser quality providers.

 

DEAR POLE BARN GURU: Hello, I’m researching putting an above ground pool in a pole barn for my swim school. I live in Oregon so my biggest concern is mold in the colder months. Do you have any ideas on this & what type of doors & windows would you suggest? It will be a 12×24 heated salt water pool. Thank you, HANNAH in HOOD RIVER

DEAR HANNAH: Thank you very much for your interest in a new Hansen Pole Building. This article should be an assist to you: https://www.hansenpolebuildings.com/2019/08/post-frame-indoor-swimming-pool-considerations/. Our factory pre-painted commercial steel entry doors and vinyl windows should work well with a proper HVAC system.

 

 

 

 

 

Cabin Design Over a Crawl Space

Loyal readers may recall recent articles guest written by recently retired Hansen Pole Buildings’ Designer Rick Carr as he designed and erected his post frame hunting cabin over a crawl space (his journey began here: https://www.hansenpolebuildings.com/2019/03/development-of-my-cabin-plans/).

Today ROB in DENVER writes:

“Hi Mike.  I was given your contact info by one of your designers; she suggested I contact you with my questions.

 I’m currently looking at options to put up a cabin in Colorado.  The location is up near Leadville at around 10,000’ elevation and the soil (I’m told by local engineering) does not have much clay; it is more a mixture of sand and rock.  Frost level up there is 4’ down.

 Question A):

 I’ve checked out some of the construction options Hansen lists and I like the option of a pole foundation but I’m a little concerned about possible shifting due to temperature changes, etc.  I definitely would want to do a raised/suspended floor with crawl space underneath (rather than building on slab).  The cabin size I’d like to build is about 24×48’ and I don’t want to have to chase it going “caterpillar” downstream since I’d have no way to raise/lower points if they’re locked into poles.

 Do you have any data/literature you could point me to and/or just provide anecdotal background from your experience putting in these types of cabins under these conditions?  I’d actually like to go 2 floors but I’m then concerned about the additional load it might put onto these poles.

Question B):  My other concern is critters tunneling in and making an unwanted home in the crawl space.  If I’m not going with concrete pad and/or block stem wall foundation around the edges, what means are available to prevent animals from digging under any skirting I’d put on and making their home in the warmer space underneath?

Thanks in advance.”

Mike the Pole Barn Guru responds:

Thank you very much for reaching out to me. We are used to dealing with all sorts of rather extreme conditions, especially temperature change, since we can go from -40 to 110 where we are located.

Question A: Temperature changes are not going to perceptibly cause any shifting of columns, unless you had conditions where frost depth would be greater than four feet and there was enough water in your soil to create a frost heave. Given soil with little or no clay, it is probably a non-issue.

Building columns are actually very strong loaded vertically. We have a lakefront home outside of Spokane, Washington where our 22′ x 24′ garage sits on 14 feet of grade change. Soils are similar in condition to what you describe. Our garage has a four inch thick concrete floor on top of a wood framework 14 feet above grade on downhill side. Above garage level we have attic trusses with a bonus room we use as office space. Below the garage level we have a 16′ x 22′ studio apartment. This building is now 30 years old and has performed admirably with no noticeable settling or column movements, even with two SUVs parked inside. I would have no undue concerns of two stories in your setting.

Question B: You could do what I did and stop the siding at the bottom of floor framing, covering underside of floor joists with OSB, plywood, T1-11 or even steel siding. In Michigan we have run into a “rat wall” ordinance on occasion: https://www.hansenpolebuildings.com/2012/06/rat-wall/. Besides solutions offered within the article, one could also use a metal rat wall – constructed out of quarter or half inch mesh (aka hardware cloth). Rolls of mesh are typically three feet wide, so you could dig a trench around your building perimeter two feet deep and a foot in width. Attach top edge to inside of pressure preservative treated splash plank then down and out into trench. Overlap at any splices and use a separate piece on each corner to provide seam corners.

Good Luck! And let me know what you did and how it worked out.

Solutions to Porch Overhang Clearance Issues

Recently KIM in STRATFORD posted this question to a Facebook Barndominium discussion group I am a member of:

“I am trying to finalize my plans today. Is it possible to have 8′ side walls and still have a 6′ overhang open porch on the eave side of the house? I have a 5/12 pitch on the house portion and actually wanted two separate roof lines, one for the house and a separate one for the porch overhang. House is on a slab so no built up foundation walls. I’m not sure if this porch will be too low with the porch roof UNDER the house roof and with a slight slope for water drainage…. Any experts out here?”

Mike the Pole Barn Guru responds:

For starters, most steel roofing suppliers will not warrant steel placed on slopes of less than  3/12. Continuing out from your main wall six feet at a 3/12 slope will place underside of your overhang at roughly six feet and six inches. Not only could this become a head ringer (at least for my son who is 6’6” tall in his bare feet), but it is going to block clear view out windows in this area. It is also just plane going to feel low.

I did some researching, however I’ve been unable to find a Building Code requirement for clearance below an overhang, however I would have to believe seven foot to be a bare practical minimum. 

You could:

(a) Build over a crawl space, instead of a slab – raising elevation of home and affording a more comfortable surface to live on (https://www.hansenpolebuildings.com/2019/03/slab-on-grade-or-crawl-space/) ;

(b) Increase house wall height – you could maintain an 8′ finished ceiling and have raised heel roof trusses to allow for full depth attic insulation from wall-to-wall (very good idea) https://www.hansenpolebuildings.com/2012/07/raised-heel-trusses/ ;

(c) Use roof trusses wide enough to span from opposite wall to outside edge of porch, with a pitch change at junction between porch and home.

Dial 1(866)200-9657 and ask to speak to a Building Designer. Your call is free and we have great solutions for you.

Thoughts on a Floor

Thoughts on a Floor:  

Brought to you by reader ANDREW in LEBANON:

“Hi! I am looking at purchasing a post frame building to use as a new home. We are well on our way with being under contract for the land and one of your recommended builders is meeting me at the site this week to make sure the land is good/flat enough.

I will be hiring the construction of the exterior and then build the interior myself.

With that said, here is my question (I will do my best to describe it by typing.) Instead of pouring a huge concrete slab (building will be 60×96), I want to do a typical crawl space to be easier to run plumbing and such, plus make changes as needed. Also, concrete slabs are expensive, especially for 5,000+ sqft. What are your thoughts? I will run 2×10 side by side (doubled up) the entire 96′ length supported every 12′ by concrete footers and building columns. This will be roughly 24″ from the ground (haven’t fully decided on the height yet). Along with that, going to 60′ width, I will use 2×8, 16″ OC. I forgot to mention, along the inside perimeter of the posts, I will be running 2x10s attached to the posts. The ends will have the 2×10 laying on top (along with concrete/building posts every 12′), and the joist ends resting on the eave sides.

With all that said (hopefully legible and not rambling), what do you think? I think it is a pretty solid plan and will not only save a lot of money by not doing a slab, I will effectively have a crawlspace. Yes, I know this will raise the entry points so the door looks like it will be off the ground 3+ feet, but I will be putting a decent sized deck on the front as well as a smaller one on the rear point of egress. A quick reply would be greatly appreciated so I can hopefully discuss more with the builder as well as for my own personal planning purposes. Thanks a lot!”

DEAR ANDREW:  I am a fan of living on wood instead of concrete, so crawl space makes total sense to me.

The right way to do this is to have your floor incorporated into the original engineered plans for your building. This will assure you of several things – the footings will be designed with an adequate diameter to resist settling (last thing you want is to have a post or posts sink. It also will make sure the size of the members will be adequate to support the loads both from a weight bearing standpoint as well as deflection. Your doubled 2×10 idea for supporting the floor joists is hugely under designed and it is very possible it would create a failure condition, not something you want to have occur in your new home.

Floor deflection is an under discussed realm (you can read more here: https://www.hansenpolebuildings.com/2015/12/wood-floors-deflection-and-vibration/). 2×8 #2 at 16 inches on center and 2×10 #2 at 24 inches on center are going to have virtually the same spanning abilities as floor joists, however the 2×10 floor will meet L/480 requirements for deflection, while the 2×8 joists just barely meet the code minimum of L/360. The added plus – the 2×10 joisted floor takes 16% less board feet of lumber and is less expensive to build!