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I want to pour the floor for blacksmith shop soon, will be an Alaskan pour 6" deep. Although I don't own one at present would like to in shop layout floor plan incorperate for a small power hammer. How thick a footer should be poured and about large. I know I haven't supplied a lot of detail,but can't at this time, shop will be about 14x10. Any thoughts or experience with this?
Adirondacker

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6" floor will be fine for just about any hammer you want to put on it, would be best to use reinforcing wire in concrete and get 4000 lb per sq" concrete and it will likely never crack from anything you want to do on it.

welder19

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If you're going to go to the effort of pouring a special slab for a power hammer then do yourself a favor and go at least 12". Most small hammers (25-50# Mech and some utility air hammers) will run fine on a 6" slab, but it is worth the extra $$ to have a good rock solid foundation that will serve you even if you chose to upgrade to a mid sized hammer. I have a 25# Little Giant with 18" of 5000 psi under it (I was planning on upgrading in the future, but when I did I kept all of the hammers), A 50" Little giant with 10" of 4000 psi under it (that shakes the shop when I run it) and a big blu 155 that used to be on 4" slab. The Blu is now on a 20" chunck because it was compacting the earth under the shop and shaking the whole building; now it runs like a top, is quieter, and hits harder. I don't think I would go 4' square, but rather go 4'x 30" x at least 12". Be sure to isolate this area from the main slab if you want to keep the hammer more quiet and minimize the risk of foundation cracking. Now dont get me wrong, you can get away with a 6" slab, but if your going to go to the effort of making a special place for an expensive labor saving machine I think it is time and money well spent doing the job correctly enough to serve you properly even if you choose to upgrade to a larger machine, and the cost won't be that much more.

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I have to agree with Jose Gomez here. If I ever get a shop of my own, I'd isolate my anvil on something substantial. The anvils and vice in the shop I'm in righr now are anchored securely to the concrete slab and we knock things off the walls and stands with hand hammers. The better backed your hammers and anvils are, the more work you will get out of them. That's just the way it is. You may never know that until you experience that.

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By "Alaskan pour" are you planning on following My floor plan? If so I'm flattered, thank you.

In that case put your main effort in the grade making sure it's solid under the slab. A well graded and compacted base will do far more for long floor life than any specific concrete. A 6" well reinforced slab will then last you a lifetime or two. for instance Bob Bergman runs both his shop hammers, a 3B Nazel and a 200lb Bradley helve on a 4" slab but the base grade is hard compacted gravel over a solid sub base so the slab is well supported and dry.

Forgetting all the fancy things I did under my shop floor, the main thing is it's well drained and heavily compacted base. I then doubled the rebar under the area I thought the power hammer(s) would go. It should be golden for anything I'm likely to acquire in the forseeable future.

AS is typical for foundation design, the base and sub base are the secret while the slab or floor are the caps.

Frosty the Lucky.

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Something else to keep you confused, what kind of soil do you have? If you live on alluvial sand and river rocks, you need to do more thinking than if you have six inches of topsoil with six feet of hardpan beneath.

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Good point Mike, soils type is very important. In fact aluvial soils often won't compact at all, the grains are too rounded and smooth, too much like a bag of marbles.

If the ground under the slab moves the slab will crack and eventually break up. Crushed gravel is sharp and angular so the grains will key together and not shift when compacted.

Having more than a % or two in the base coarse is a bad thing but not having any isn't good either.

Soils mix design is a pretty involved thing needing samples, lab tests, etc. to do properly. The good thing here is, a small shop like yours or mine isn't as demanding as a road. That said, without being able to look touch and do a couple field tests there's no way I can suggest what your soils might need done. Hopefully they're good as they are and only need a little compaction and maybe a few inches of D1 to be perfect.

Frosty the Lucky.

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What about a situation where the slab has already been poured years ago and you have to live with it. For a small hammer, say a 50# or less, would a wood base be a good alternative that has been bolted to the existing slab? Money is always an object to be considered and it would be to expensive to take apart the barn, cut out a section of slab, and re-pour that part. The old slab does have rebar and wire mesh in it and is about a 6" pour.

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Thank you for reinforcing my thought process, I will isolate a footer in the event I someday end up getting a power hammer. I'll have to be careful on shop layout to keep that space free from something permanent. Frosty, you are welcome, Alaskan pours are handy, yet for some reason are frowned upon here in N.Y.? Here you either have to be on top of the ground or down 4ft. this shop will be heated so frost heave is not a problem, its going to be attached to garage. I will come up with 3 courses of block then frame walls with 2x6, door opening will be on the north side of building, I want ceiling height as high as possible, was thinking over head door but will be in the way when open so will have two hinged doors. As this project starts will try and post pictures.
Adirondacker

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Great advice on slab and slab prep!!!

A word of caution on the "barn" doors. To have doors big enough to be serviceable, they will be VERY hard to hang and keep true enough to keep mice and other small critters out of your shop. When I purchased my building kit, it came with sliding barn doors. My neighbor (who has the same building kit and barn doors) has rats as big as small cats :angry: in his shop.

I upgraded to a rollup door and there are only 2 places in my building where mice and lizards can get in. Thats in the jamb set for the steel entry door. There is an opening in the end (bottom) of the formed jambs that is about 1/2" x 1 1/2". I usually get a few mice a year around the change of the seasons.

Just thought I would mention this- there is nothing worse than going for your favorite pair of earphones only to have one of the foam pads eaten by a mouse :blink: :blink: or opening a drawer to reveal a family of 5 :lol: :lol:

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What about a situation where the slab has already been poured years ago and you have to live with it. For a small hammer, say a 50# or less, would a wood base be a good alternative that has been bolted to the existing slab? Money is always an object to be considered and it would be to expensive to take apart the barn, cut out a section of slab, and re-pour that part. The old slab does have rebar and wire mesh in it and is about a 6" pour.


There are a couple advantages to a wood hammer base, especially if it's an old one like my 50# LG. Putting mine on 4x12s not only means the hammer can NOT transmit sharp shocks to the slab but it raised the lower die to a better height.

Sometimes you just have to work with what you have. Without knowing what the base is like under the slab or maybe what the slab itself is like spreading the weight and impact over a larger area through a little cushion certainly can't hurt.

Frosty the Lucky.
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i was under the impression that in alaska they don't cut into the permafrost but pour pretty much on top of the ground.


That depends. Most of Alaska hasn't had permafrost for a couple centuries at least, maybe millenia. Not to say most of the area in AK still doesn't have at least some but the real population centers don't.

Then there's type. Technically permafrost is any soil that maintains a below freexing temperature year round. If said soil is dry gravel being cold has zero effect on it as a stable foundation. If it's "till", sandy, silty, cobbley, bouldery, gravels deposited by glaciers and then ground into the hardest non-consolidated soil formation on the planet by a couple miles of ice vibrating over them for a few tens of thousands of years, being frozen only makes it harder. WAY harder.

If on the other hand the permafrost has a high water table there isn't a whole bunch you can do to keep a foundation from moving from seasonal freeze thaw.

There are soils types that are super susceptible to water and freeze thaw which makes almost any construction a serious challenge.

There are lots of strategies for building on permafrost or FS (Frost Susceptible) soils. FS means it's going to move, grow, expand and contract, pump water, etc. etc. as it freezes and thaws. For a long time and continuing now, NOT impinging on permafrost was thought to be the only way to build in permafrost country. It's not, there are techniques that work much better but are much less PC.

Okay, what happens when you build a heated structure on permafrost is it can melt the ground and sink. Heated can just mean sheltered from external ambient temps and catching some solar heat. It really doesn't take much. The do not disturb method is largely SOG, (Slab On Grade)with no proper footer and the only way it's effective is if it's heavily insulated.

Another really cool foundation type is floating, lots of bridges here have floating foundations simply because the soils have above liquid limit water content and there is deep freeze thaw. Freeze thaw under these conditions will literally jack pilings out of the ground almost no matter how deep they're driven.

Then there are the deep pile foundations. These generally work really well if a few things are done. First drive them to physical refusal. Normal pile refusal refers to the energy needed to advance it exceeding the expected load and safety margin. Physical refusal means the pile literally can not be driven any farther and is indicated, not by how many blows per foot the hammers administering but by the top foot or so of the pile crushing into steel ribbon candy.

Once at physical refusal a pile is typically socketed into a hard non-mobile strata. Still, given time freeze thaw can jack em so keeping the ground from thawing is the order of the design. If the pile above ground has vents that allow air to circulate, any time the outside temperature is below ground temp cold air will flow down into the pile reducing ground temp even more. Lastly build something on or over the pile that keeps the ground shaded.

There are more high tech versions of keeping the ground frozen, one of the best examples I know of is the Alaska pipeline. All the pipe support structures are on piles but not really deep. However, they do have anhydrous ammonia refrigerant filled heat exchangers that will maintain near zero f temps when the ambient air temp is as high as the 80's.

For non-permafrost ground conditinos all there is to worry about is seasonal freeze thaw and here we deal with it just like anywhere else in the USA. Footings need to be a minimum 42" in nfs (Non- Frost Susceptible soils)and generally deeper in fs soils, a soils lab can test and make recommendations or offer a proper design.

Darn, the more I write about this the more I remember about it. That's what I get for spending 20 years in the state of Alaska's materials geology and foundations section. I started as a lab rat and after getting tapped more and more often to help the drillers in the field and do any fab work or repairs on the drills I ended up transferring onto the bridges and foundations drill crew.

Ah what the hey, you guys know what it's like to get me going.:blink:

Frosty the Lucky.
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Great advice on slab and slab prep!!!

A word of caution on the "barn" doors. To have doors big enough to be serviceable, they will be VERY hard to hang and keep true enough to keep mice and other small critters out of your shop. When I purchased my building kit, it came with sliding barn doors. My neighbor (who has the same building kit and barn doors) has rats as big as small cats :angry: in his shop.

I upgraded to a rollup door and there are only 2 places in my building where mice and lizards can get in. Thats in the jamb set for the steel entry door. There is an opening in the end (bottom) of the formed jambs that is about 1/2" x 1 1/2". I usually get a few mice a year around the change of the seasons.

Just thought I would mention this- there is nothing worse than going for your favorite pair of earphones only to have one of the foam pads eaten by a mouse :blink: :blink: or opening a drawer to reveal a family of 5 :lol: :lol:


Don't the mice, lizards and such help keep the cats fed?

Frosty the Lucky.
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Why don't you pour a 4" slab in most of the shop and pour a dedicated footing for a power hammer that is isolated from the rest of the floor.

Use strips of some kind of rubber , wood or fiber sheet to make a gasket between the slab and the footing. The rebar should not connect the two . Make the footing at least 3 feet square and at least 18" deep. Use extra rebar in the PH footing. That should be plenty adequate for any kind of hammer that would fit in that small of space .

Locate the footing by making a generic template of a power hammer and locate the bulk of the footing under the anvil. You want as much access to the hammer as possible, both straight through the dies as well as across the length . Mock it up with as long a bar as you are likely to be working under the hammer. It will be hard to really get it right without the actual hammer. A few inches either way or a few degrees change in orientation can make a huge difference in usefulness and efficient use of space. This becomes even more critical in such a small shop

Having a separate foundation for the hammer will make a noticeable difference, both in how hard the hammer hits and how much vibration is transmitted to the rest of the building.

Put a wood pad under the hammer. If you don't have the hammer when you pour the footing and are able to cast the anchor bolts into the concrete. you can set the anchor bolts into the existing footing using something like Hilti system epoxy .

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Frosty: "Sometimes you just have to work with what you have. Without knowing what the base is like under the slab or maybe what the slab itself is like spreading the weight and impact over a larger area through a little cushion certainly can't hurt."

Thanks Frosty for the advise. What would be a minimum thickness of wood be for a 50#LG hammer? Are you talking about 1/2" plywood, 3/4" or 2X4's with plywood on top?

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I'm offen accused of over building thats why a 6 inch slab,outside of footer will be deeper to support the building. No perma frost here but frost line is about 4ft. Soil here is mostly hardpan and rock so if left alone won't move. I might be able to use a sliding barn door will have to think about that as it might interfere with sawmill operation. The footer for power hammer I could fill in with wood for now until that time I get a hammer, do like the idea of trying it out before deciding where to put the footer, once its poured you have to live with it.(been there done that) to old to settle. They make a fiber board that is use for expansion joint so will use some thing like that to isolate the two footers. Half the fun is in the planning the other half is using it everything in the middle is just work. Have been two men killed here this month working in the woods with farm tractors, I use a 1956 ford 600 for skidding is set up with hyd winch and has a heavy roll bar but no roof so am in the middle of building a cab over this tractor, wife got me a lincoln mig welder so am going thru a learning curve as well as tips trying to get the hang of it. I just stopped to jot some lines as frustation was getting to me. Also have a 440 jd dozer with nothing over it, so thats next. Both men were late fifties early sixties had been around farm equipment just made a mistake. Want to go out at ninty shot by a jealous husband.
Later Adirondacker

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My cat is lazy. The only wet food he will eat comes in a can :lol: :lol: :lol:


Stop feeding him/er so much and then lure the mice into the shop bathroom.

Hungry cat, food in the can, problem solved. I wish all life's problems were so straight forward.

Frosty the Lucky.
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Frosty: "Sometimes you just have to work with what you have. Without knowing what the base is like under the slab or maybe what the slab itself is like spreading the weight and impact over a larger area through a little cushion certainly can't hurt."

Thanks Frosty for the advise. What would be a minimum thickness of wood be for a 50#LG hammer? Are you talking about 1/2" plywood, 3/4" or 2X4's with plywood on top?


Oh yeah, you do what you can with what you have, it's called Life.

I used 4x12s and made long through bolts from all thread to connect them edge to edge. The pics show what I made before I tipped the hammer up on the floor. The steel straps are backers for the anchor bolts to the hammer base. If I do it again I'd make it a little wider, my hammer rocks side to side a little in use. If I'd bolted it to the floor it wouldn't rock but I have too much stuff in the floor, stuff like hydronic heat tubing which just doesn't like having holes drilled through it.

I don't have a pic of it but the hammer has an angle iron anchor lag screwed into one side of the wood base that has a 2" sq. pipe that slips into one of the shop floor gozintas. The hammer rocks a little but stays put so it's good for now.

This is just what I did and I think it'd go a long ways to minimizing damage to a slab even if it's over a poor base.

Frosty the Lucky.

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post-975-069957500 1274575908_thumb.jpg

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I want to pour the floor for blacksmith shop soon, will be an Alaskan pour 6" deep. Although I don't own one at present would like to in shop layout floor plan incorperate for a small power hammer. How thick a footer should be poured and about large. I know I haven't supplied a lot of detail,but can't at this time, shop will be about 14x10. Any thoughts or experience with this?
Adirondacker


I believe the Little Giant web site has floor plans for the various LG trip hammers.
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