Adding concrete floor to existing pole barn

[racerboy]

Went and looked at a farm over the weekend that checked all the boxes as far as barn, ring, pastures, etc. the only thing missing was a shop. There is a pole barn (45x36) that is on a dirt floor that I thought could be converted, but it would need a concrete floor. I’ve included a picture below. Can this be done? I know the ideal situation would be to build the shop on the slab, but can a slab be poured ‘in’ a building like this? It would need insulation, Sheetrock, electric (has sub-panel already) water, but those seem relatively easy compared to the slab.

Due to ‘impervious coverage’ restrictions, I would not be able to tear this down and start fresh. I believe this property already exceeds the max impervious coverage. If I knock down this equipment shed, I would not be permitted to simply replace it with a new one, so the best I could do is improve the existing structure.

 

[billconner]

Sure. A lot of pole barns are retro fitted with slabs.

 

[racerboy]

Ok. I figured it could be done, but wanted to confirm. Our Realtor is confirming with the town building department that adding the slab to a pre-existing structure does not increase the impervious coverage. Logic dictates that it does not, but want the municipal officials to acknowledge that. I had no idea that a gravel driveway was considered impervious. This property is a flag lot with a pretty long driveway that significantly contributes to the pre-existing impervious coverage.

Two other quick questions. How long after a slab is poured would I be able to install my service lift, and place my storage lifts on the slab? I’m assuming slab would be 4 inches thick. Does that sound right?

Also, someone told me they make pavers that are considered ‘pervious’. Has anyone heard of this? How can gravel be considered impervious but a paver is pervious?

 

[ConCretin]

Two other quick questions. How long after a slab is poured would I be able to install my service lift, and place my storage lifts on the slab? I’m assuming slab would be 4 inches thick. Does that sound right?

A 4" slab is plenty adequate for most uses because it's the ground under the slab that's actually supporting all the weight you put on the slab. For that reason it's important you assess your base before you do anything else. In geotechnical terms, the loads we're talking about are pretty modest but you want your base to be free of organic material, uniform, stable and fully compacted.

Concrete theoretically doesn't reach design strength for 28 days although in recent years it's not unusual to see design strength in seven due to conservative water/cement ratios and water reducers. The concrete itself will be able to support a lot of weight pretty quickly so if we're talking 4 post lifts, I'd give it a week, If you have a two post lift that depends on anchors into the concrete, I'd give it a least two and maybe even four to be safe.

Take a look at my Guide to Floor Slabs in the link below for some additional thoughts on placing your slab.

 

[billconner]

I don't understand the impervious gravel either.

I think key is revelation of finished slab in relation to rat board/ bottom tier. I believe you do not want the slab at top of girt, but about 4" below. You probably will have to remove some ground from what is there and then some gravel and compaction.

Sounds like a great property.

 

[ConCretin]

Having gone through a recent DEP permitting process I can confirm that here in Maine at least, gravel is considered impervious presumably because it sheds storm water rather than absorbing it. All of our compacted gravel driving, parking and storage areas were classified as impervious but other areas that had actually had organic material growing out of them were too because the soil was gravel-like.

I'm not familiar with pervious pavers I am somewhat familiar with pervious concrete. It's not designed for something like a building slab but rather for parking areas. They basically eliminate the fine aggregate and replace it with a chemical that works with the cement to glue all the course aggregate together. If you dump a 5 gallon pail of water on the stuff, it just disappears. I assume the pavers are similarly constructed, How long before all the little voids fill in with road sand is another question......

I suspect the OP's slab won't add to his impervious area because it's already included because it's under a roof.

 

[Improved700]

I did the exact thing about 15 years ago in my 30 x 60 building.
Started as a dirt floor building, and poured 4 inch of concrete.

Dug out old dirt, added gravel and compacted it down. Used laser to help
set heights, and once all was good, poured and finish.
If I remember, it was like 24 yards or something. 3 trucks.
Wheel borrowed most of it, and took our time. Total of 4 guys.
Nice thing is when it comes to finishing, most of it is covered, and out of
direct sunlight, so not fighting that time crunch.

As far as your service lift's, you will want to check with lift MFG for their requirements,
for the posts, but the rest of the area can certainly be 4 inch thick.

No regrets, and you will love it.

 

[dcg9381]

Sure. A lot of pole barns are retro fitted with slabs.

I'm seeing pole barns that are being constructed with concrete "after" intentionally... That's not usually how we do it here, but it's a thing.

 

[Youngandfree]

I'm seeing pole barns that are being constructed with concrete "after" intentionally... That's not usually how we do it here, but it's a thing.

Got to wonder if it gets signed off as an equipment shed with no concrete for a lower tax valuation?

 

[billconner]

Could be reason for bigger door - to get concrete truck in rather than pump or buggy or wheelbarrow.

 

[racerboy]

Thanks for all the replies! I’ll definitely check out the Guide to Floor Slabs.

The pervious pavers were not for the building but would be used as entrance in front of the doors (which is his grass at this point). The building has two large sliding doors on the gable ends (I think that’s what they are called. Could I also add a door(s) to the front so I could just pull straight in?

 

[billconner]

Grass pavers is what I call them. Not cheap. Concrete and plastic at least. Pervious on a macro scale, mot like LLWillys pervious concrete on a micro scale. I don't think they make a great garage floor unless only parking things in it.

 

[kbeefy]

I had a slab poured in a pre-existing pole barn at my last place, and the one I have now also looks like it was poured after the fact.

 

[kbeefy]

Last place shortly after slab was poured....

 

[Kpaige]

If your pole barn is a true pole construction the slab is almost always poured after the poles are in and metal is up. Only difference is your dirt floor has had a lot of time to settle and pack which if it’s the right material is awesome for pouring on. Stick frame the concrete is poured before the building is up.

You may need to do some exterior detailing with the bottom metal etc after the floor is poured.

 

[The Cobbler]

hope it works out for you , and you get a positive reply on the impervious coverage . as others have said, adding a pad will be easy to do .

 

[olytdi]

What Kpaige said. Here's mine...

 

[racerboy]

Very cool pictures. Really appreciate the feedback. I’m not sure the deal is going to work. I know it’s a Seller’s market, but they want the property sold ‘as is’ and still want top dollar. Crazy times. I’ll keep the team posted. We will find a farm eventually. We are in no rush. My step-daughter is a junior in high school and we are keeping our house until she finishes high school and goes off to college. This particular property just ticked all the boxes for both horses and cars.

 

[larry_g]

If you look through my build thread you can see that the poles and the roofing was on, then the concrete was poured, followed by the siding. So yes you can do the floor in an existing building. We poured to the top of the lower girt and used that for one end of the screeding board. build is linked below.

lg
no neat sig line

 

[olytdi]

Very cool pictures. Really appreciate the feedback. I’m not sure the deal is going to work. I know it’s a Seller’s market, but they want the property sold ‘as is’ and still want over ... Crazy times. I’ll keep the team posted. We will find a farm eventually. We are in no rush. My step-daughter is a junior in high school and we are keeping our house until she finishes high school and goes off to college. This particular property just ticked all the boxes for both horses and cars. lol

Wow! . Well, I used to live in Bucks County from the '60s into the '80s and prices were crazy even then.

 

[rockettauto]

I'm seeing pole barns that are being constructed with concrete "after" intentionally... That's not usually how we do it here, but it's a thing.

Got to wonder if it gets signed off as an equipment shed with no concrete for a lower tax valuation?

Same here. Even with metal buildings.

Main reason here being that beyond a certain size, code calls for full footers as if it's supporting house walls. Despite how the building is actually supported.

Basically the slab is treated as a parking slab if it's poured after and the walls don't sit on it

 

[racerboy]

So the deal didn't go through. We were outbid, But this was still very useful information for want the next farm comes along. Thanks so much to my GJ peeps.

 

[finn]

The 16’x60’ pole construction blean to on the back of my shop had a sand/gravel floor when I bought it. I had a 4” concrete floor poured about four or five years ago. Cost $5k at the time, but was worth every penny .

I also had a 12’x12’ commercial quality door installed at the same time. All in all, it was a relatively inexpensive to get almost a thousand sq ft of secure storage and workspace

 

[Captain Spaulding]

I'm seeing pole barns that are being constructed with concrete "after" intentionally... That's not usually how we do it here, but it's a thing.

I’ve never seen on built any other way. When you pour after, the skirt boards are the forms and you don’t have to worry about rain. Nail boards across the doors, fill to level with 53s and pour the concrete. Soil isn’t disturbed so you have a good surface under the floor.

 

[NUTTSGT]

So the deal didn't go through. We were outbid, But this was still very useful information for want the next farm comes along. Thanks so much to my GJ peeps.

Even the deal didn't go through, this is probably what the finished pervious paver driveway will look like.

Grass pavers is what I call them. Not cheap. Concrete and plastic at least. Pervious on a macro scale, mot like LLWillys pervious concrete on a micro scale. I don't think they make a great garage floor unless only parking things in it.

 

[BlindViper]

According to the code official when I was building my shop the deck on my house (25' x 25') counted towards my impervious totals. Doesn't make sense to me because the water goes though the slots?

 

[iagsxr]

So the deal didn't go through. We were outbid, But this was still very useful information for want the next farm comes along. Thanks so much to my GJ peeps.

I don't think anyone mentioned this, assuming you get frost you would have needed to put footings in the big doorways. Floating slabs move too much to be under a door that size., at least in my climate.