Tag Archives: concrete saw cuts

Building a Barndominium on an Existing Concrete Slab

Building a Barndominium on an Existing Concrete Slab

Whether a simple pole barn or an elaborate barndominium, shouse or post frame home, there are some challenges when it comes to constructing on an existing concrete slab on grade.

Reader NATHAN from PITTSFORD began this article when he wrote: 

“I have a 28x 80 foot pad. How hard would it be to build a pole barn house on the pad. It has a singlewide trailer on it now but want to build on this pad.”

While an existing concrete slab may be able to be integrated into a pole barn or barndominium as a floor, in most instances it will be inadequate to structurally support any structure, unless it has been specifically designed to do so in advance. In most cases, it will need to have been placed with a Building Permit and have had appropriate inspections by a Building Official.

Concrete slabs, such as Nathan’s, can be a resultant of several different circumstances. In his case, it appears to have been poured merely to park a manufactured home on it. Other times they have been poured with an idea of placing a future building upon, however without (in most cases) adequate structural considerations. I have run into more than one person who has an existing slab as a result of a previous building having burned down.

Usually I would avoid attempts to erect a structure on top of an existing slab unless I knew it to have been adequately designed and properly inspected, or knowing a Registered Professional Engineer had done a thorough inspection to determine adequacy.

If able to support a building, dry set anchors can be used to anchor columns in place (read about dry set brackets here: https://www.hansenpolebuildings.com/2014/12/dry-set-column-anchors/).

For flat slabs, without curbs or raised perimeter foundations, square holes for columns can be cut with a concrete saw to allow for holes to be augured and columns placed. Space between columns and saw cut edges can be later filled in with concrete.

A simple solution, for those who feel they must use their existing flat slab, is to build outside of slab edges. This allows for holes to be dug, without any need for concrete cutting.

Have an existing slab to be incorporated into a new post frame building? Please call 1(866)200-9657 and speak with a Building Designer today.

Fear of Concrete Slab Cracking at Post Corners

Fear of Concrete Slab Cracking at Post Corners

Nothing appears to add to the self-importance of a contractor more than instilling fear into the hearts and minds of their clients. If I had a dollar for every fear mongering story I have heard over the years, I would be a wealthy man!

Hansen Pole Buildings’ client PAUL writes:

“Hello, I’m Paul in McCall Idaho and I purchased a 14′ x 36′ pole building last fall from you and I had a quick question.  I am getting ready to pour the concrete floor and the concrete guy helping me was concerned that the floor will crack on all the post corners and wants to do some changes to prevent it. I have never heard that that was a concern and thought I would consult you guys as I know you’ll have the correct answer. SO, is that something to be concerned about??  Thanks for the help and I know my account is closed by now but figured you’d have a quick answer for me.  Thanks a lot.”  

Mike the Pole Barn Guru responds:

We’ve never heard this as a concern either, so perhaps you can get your concrete finisher to share research studies he has read which elaborate upon this supposed challenge. I personally have owned (or still own) several post frame buildings with concrete slabs and have never experienced issues with floor cracks other than where they are supposed to be – along control joints or saw cuts.

The most important things to avoid cracking where not desired is to have dedicated allowance locations for cracks (e.g. expansion joints or saw cuts should be located every eight to 12 feet for a four inch thick slab), have a properly prepared and well compacted site, eliminate sources of water which would or could flow under the slab, reinforce the slab (by use of one or more of the following – fiberglass strands, wire mesh, rebar) and to have the slab tied into the columns by use of rebar hairpins through the columns. The clean sand between the vapor barrier and the concrete should be moistened prior to the pour as well. Concrete mix with too much water in it will lead to future cracking. It is more work to pour with less water, but the end result will be far better. Keeping the slab well hydrated (water on top of the slab) for the first month after the pour will retard the speed of curing making the slab not only stronger, but also will reduce the cracking.

When I was building myself, one thing I would always guarantee with concrete slabs – they will, at some point, crack. It’s the nature of concrete.