Concrete engine Shed base

[veggie]

Hi all,

When pouring a concrete pad as a floor for a small engine room ( say 4ft X 8ft ) do most people pour the pad as a floating base on packed gravel ?
... or is it advisable to pour 4 to 6 sono-tube piles with rebar heads and then pour the floor over the piling heads.

Considerations....
Engine vibration
Floor thickness (I propose 4")

Anyone poured a small generator room floor on grade ?

veggie

[BruceM]

Most sheds here get a monopour slab with thickened edges, in lieu of full footings.  For an engine shed, you could think about isolating the engine mount section with some foam board, or just assume you'll isolate the engine base from the slab otherwise. 

[LowGear]

I agree with BruceM.  You'd need footing band for a "J" bolt or fastener of some sort.  I do know a couple of people that would just nail the plates to the concrete the day you pull forms (one or two days after the pour) but the vibration might put a new wrinkle on that methodology.

Isolating the engine pad sounds like a smart idea as well.  But I just might consider a 12" thick pad for that few cubic feet. and how many people have complained about their generator station being a few inches higher than the rest of the floor.

And remember; re-bar doesn't prevent cracking but does stop migration of the pieces.  And some of that fiberglass stuff couldn't hurt.

Good luck,

Casey

[Tom Reed]

When my engine shed was poured, a mono slab with thickened edges was done to support the shed and a rectangle was formed where the engine block would be poured. After the slab dried, the forms were removed for the engine mounting block and the hole was dug deeper by about 12" and lined with a corrugated poly sheeting I had. This isolated the engine block from the slab. The engine block is raised about 10" above the slab floor to facilitate working on the engine.

[BruceM]

Lovely base concrete, Tom.  

Just thicker concrete was something I tried- 10" deep in the area of my engine on my 10x10 shed- the "House of Lister".  Pretty hard ground- dense clay/gravel/sand mix. This didn't stop my non-jackhammer 6/1 Listeroid from vibrating the building. (Balancing did.)

So I like Tom's approach with the isolated slab for the engine- which helps with isolation AND raises the engine to a more comfortable working height.

I'm not sure it's always necessary, especially as Veggie tends to have very well engineered engine setups, isolation mounts, etc.  

My only other comment that in the entire recorded history of man, not one man has every complained about an engine shed being too large.  I love having storage space right there for parts, spares, a dedicated set of essential tools, and fuel.  It's just not that hard to make it a bit bigger- there's still 4 corners and a door and a roof, so you're adding the easy part.  

[yellowhead]

Hi Veggie. Long time no see. My 8x8 foot shed was built on a 5 1/2 " (2x6 form) slab poured on grade with rebar on 2 foot centres. Survived the best part of 1000 hours of Changfa pounding with the set resting on a couple of 1/2 inch thick pieces of horse mat. Still looks as good as new except for the oil stains ...

[veggie]

Thanks for the tips everyone.
I think I will forgo the pilings and go with a monlithic pad and rebar (floating and thicker at the edges).
As BruceM mentioned, I will most likely be using rubber isolation mounts under the gen set.

Picture to follow once I get moving on this.

veggie

[mike90045]

I've seen Tom's setup, with a raised portion the elevates the engine to a more workable/maintainable height, and it's nice. 

I mounted my I beam frames on top of some oak flooring planks, to isolate the metal from the concrete. I think it helps some.  Just resting the frame on a stall mat, did nothing, it still bounced around.

[Tom Reed]

As nice as that setup is, the dishes in the kitchen still rattle sometimes. However it does pass the wife test as from time to time she'll ask if the generator is running. Sometimes it is and sometimes not. I sure hope we gets lots of dark rainy weather this winter, after 8 years I still get a kick out of running it. It's a disease I tell you.

[Ronmar]

I like my mount separate from the floor.  I have yet to see a slab that didn't crack at some point.  How would you feel about a crack thru one of your Jbolts on a 4" pad?  Wouldn't give me a warm fuzzy...  The shed was something else before I got here, and I may want to use it for something else someday.  When I do this again, I will do it similar to how I did this one. I will pour the pad and build the shed.  Then come back and put together a wood form setting on a rubber horse stall mat, and pour the block for the engine base with mount bolts and one or two layers of re-enforcement grid tied to the Jbolts so their load is spread out thru the whole block making any cracks less of a structural issue.  My current base is just under 1 foot thick.  It was the front porch block of my current home, re-purposed to an engine base when I built a new large porch deck.  Next time it will be a little taller as starting is way easier on the back with the engine a little bit elevated, not to mention maintenance in general...  The block on the rubber pad seems to isolate the thump of a power stroke pretty well.  I can barely feel it inside the house, and my generator shed is only about 15' from my bedroom.  Need to repurpose the shed?   Gen, engine and mount block get fulcrum and levered up onto pipe rollers and roll out the door on 2X4 rails with the push from a finger egyptian style, just like they went in...

As always my .02