Concrete sawmill pad --- 14 x 4 x 6" --- what not to do

[OffGrid973]

I have a guy quoting me a price to frame and pour my slab and I was curious if any good threads exist on this. (My searches are failing to find em)

Any "do nots" that I should be aware of like one full slab vs expansion joints.  Is 6" too deep and 4" will do for a Woodmizer LT-10.

Laid the gravel end of last year,  now just need to pour and a truck can drive right up as it's right off the driveway.

[ChugiakTinkerer]

Considering you could probably operate just fine on packed gravel, I reckon your concerns are more aesthetic than structural.  The concrete will crack, so you should put in some contraction joints every 4'.  Well, make it 4.67' and you'll have three panels that will be almost square.  I don't think an expansion joint is warranted on a slab that short.  And you certainly can get away 4" thick unless you plan on some insanely large logs.  Just my thoughts, from a guy with no particular expertise.

[DPatton]

Cwimer, CT is correct about the contraction joints. I would also add some wire mesh or small diameter reinforcing bar to keep this long narrow pad in one piece.
Two thing are absolute about concrete. 1, its going to get hard. 2, its going to crack. Properly placed and sized contraction joints will control where it cracks. Properly installed mesh or reinforcing will keep the cracks from shifting or moving around.
As far as thickenss is concerned it depends on how heavy your mill and logs are. Or if your will ever be driving up on it with a loader or tractor. I would suggest a 5" thickness if you want something a little heavier than 4".

[Ljohnsaw]

And don't forget you can opt for stronger concrete mix.  The standard is "4 sack" (I forget the compression strength numbers) and I will often pay the extra $10 or so per yard to make it "5 sack".  Remember that you want the concrete mix a stiff as possible.  Extra water makes it easy to work, but also greatly weakens it.  +1 on the remesh.  I did several 12' x 24' slabs with remesh and NO expansion joints.  Only one small hairline crack in a 4" thick slab with 5 sack.  Also, in this barn, three 5' wide x 48' long slabs for the isle (sunken middle for rubber mats).  Remesh and NO expansion joints and no cracks.

How wide will your slab be?  Just enough for the wheel base (or feet)?  Will you have dirt or gravel next to the slab or will it be a step up from the ground?  You need to think how the slab will affect your working height.  Would it be better to pour a wider slab so you have something smooth (and not muddy?) to walk on when working?

[dustyhat]

Lots of metal, i think you can get it mixed with some type of fiber but i have never used it ,it may be higher than using metal though.

[4x4American]

From what little knowledge I have on concrete, I seen a few sawmills have trashed sides where the loader drives up onto the concrete so I would suggest digging a haunch around the perimeter to make it extra more strong

[YellowHammer]

What everybody else says, form it well, metal mesh to keep parts of it from walking off, make it bigger than you need, and mainly, control the edges as they can become a real tripping hazard (which isn't good around a mill) by fairing them into the grade, or sloping the concrete to the grade, as well as a thicker edge footing to keep it from cracking at the interface from dirt to slab.

[Larry]

That's such a small slab no cutting required and may be detrimental.  #4, that's 1/2" rebar should be placed on 12" grid using chairs to hold it off the gravel.  Tie the rebar with wires.  The rebar will keep the slab from moving if it does crack.  Forget about fiber reinforcement, that's to control shrinkage cracking only.  4" thick will be fine.

The slab is so small even beginners could finish without much problem.

[ChugiakTinkerer]

Cwimer,

I looked in your gallery and I think this is probably how your workspace is currently set up.



If you keep the slab narrow enough then you will be walking on the driveway and not the slab.  Tripping shouldn't be an issue while operating the mill but you still want to keep that transition from slab to driveway smooth.  Minimize stubbed toes and all that.  I'd want to have a little crown on the slab so that rain sheds easily and doesn't pool.  If you end up with standing water during freeze-thaw cycles your concrete will spall much more quickly.

[Sixacresand]

After the concrete set up, you hammer drill holes to add anchor bolts

[OffGrid973]

Thanks guys...I priced things out and may give it go myself, just afraid of not being able to mix and pour fast enough.  Having a truck stop over requires a big # and getting leftovers from a big job is tough to coordinate. 

You guys suggest any kind of plastic to hold liquid in like making concrete countertops or just right onto the 1x6's is ok on top of the rock?

[Ljohnsaw]

You don't need plastic.  That is just used for a slab where you don't want moisture coming up - like a basement.  Just right on the rock is fine.  Also, 1x6 won't be good unless you use a LOT of stakes.  2x6 would be much better.  Also, place a wooden stake at an angle so that it touches the top of the form boards in addition to the normal vertical stakes.  Screw this in to provide a brace to keep the forms from tipping out when the concrete pushes on it.  Also, when you pour the concrete, bang the boards to get it to settle well with no air pockets against the boards.

You should look at getting a trailer cart of concrete - you will not like mixing all that concrete!

[OffGrid973]

Is a trailer cart a smaller version of the truck with a hose?  Thx for advice on 2x6, having a flood would not be optimal.

[DDW_OR]

here is a link to my Central Boiler install, it has info on how i did the pad
https://forestryforum.com/board/index.php/topic,92218.0/all.html#top



 

[Ljohnsaw]

Is a trailer cart a smaller version of the truck with a hose?  Thx for advice on 2x6, having a flood would not be optimal.

No.  Check out "redi mix" type suppliers in your area.  They will have one of two types of trailers.  They will be tandem axle (4 tires) and equipped with surge brakes on a 2" ball hitch.  They may limit you on how much they will load based on your tow vehicle.  I've had some places say they will only do 1/2 yard with a 1/2 ton pickup.  One type is a open top box with a sort of spout and a manual hydraulic jack to help you dump it into wheel barrows or directly into your forms if you can back up to them.  The other is a rotary drum (like a mini cement mixer truck) that is run by a gas engine connected to a hydraulic pump.  There are controls to adjust the speed of the drum and to dump the load.  I prefer the mixer type - especially if you have to drive a bit.  Concrete in a plain dump trailer tends to get pretty stiff from the vibration during the trip.  Never add more water to the mix unless it is really dry.

[paul case]

Most redi mix trucks would have no problem putting the mud in your forms as quick or as slowly as you want to go. They may have a minimum, 2 yards here. but by my calculations you only need 1 yard. I would dig a little footing around the inside of your form to give it a thik edge and then fix up a form for extra to make sidewalk or???? so that you waste nothing. Redimix concrete for flooring here is about $90/yard delivered.

If you plan to do this yourself it would be invaluable to you to go watch someone else finish concrete before you do it. You can make a fine sawmill pad by screeting off the forms and floating it and when it is almost set trowling it or a soft broom finish.

PC

[fishfighter]

If it was me, which I am planning to do a slab, I would go wider then 4'. My plan is to go as wide as 8'. Reason, a place to walk along both sides of the mill and easy to clean up saw dust off concrete.


As others pointed out, a 4' slab has tripping in your future unless you grade up to the edge of the slab. Putting down rocks has a very good chance of getting rocks in your logs. Rocks and saw blades don't mix well.

[highleadtimber16]

I would suggest making the slab wider. You want to walk on the concrete, not in mud and wet sawdust. Mine is 18x40' and still, never enough room. I didn't use any metal and it hasn't cracked, but it's not a bad idea to use some in yours.

[Bruno of NH]

Do you have one of the trucks in your area that comes to the site with the dry mix and then mixes only what you need?
They tend to be less money than the ready mix companies.

[jmouton]

i have been doin concrete for almost 30 years now ,,,,  make the pad bigger  10 x 20 youll need it,,,  mesh has its drawbacks and advantages ,, its a 50/50 ,,  4 inch its alright ,,,   just place it in when you pour it ,,  no chairs ,waste of money,,, if you go with 6 inch ,,,better  in my opinion ,,  just run some  rebar lengh ways  num 4 ,,,,half inch ,,just place it in,,,,dont try to mix it with redi mix ,,,, way too much work and you wont keep up and not as good as standard 6 bag mix with a compression strength of over 4000 psi at 4 in thick ,,4 bag is not standard for flatwork,,,, 2500 psi is for footings ,,   just my 2 cents worth of 30 yrs of knowledge ,,,,

[jmouton]

oh and the only guarantee that we have is , that concrete will crack ,,even with wire or bar in it ,,

[Jemclimber]

Jmounton,

When you say mesh, are you referring to fiber mesh?  Can you tell me the drawbacks besides increase in price.   

I've busted up my share of concrete and without chairs the rebar was always on the bottom.  I know most guys say they pull it up, but from what I've seen when removing it, it doesn't happen.

[fishfighter]

Jmounton,

When you say mesh, are you referring to fiber mesh?  Can you tell me the drawbacks besides increase in price.   

I've busted up my share of concrete and without chairs the rebar was always on the bottom.  I know most guys say they pull it up, but from what I've seen when removing it, it doesn't happen.

I always wire tie in bricks under the wire to lift it off the ground. ;D

[bandmiller2]

Seeing as your next to your drive I would consider attaching it to your drive with a lead in, then if the mill is removed you can park on it. Would pay to make it wide enough to park a car or truck on. Frank C.

[Ljohnsaw]

I always wire tie in bricks under the wire to lift it off the ground. ;D

I visited a construction site and the boss said I could have whatever was in this big pile.  I got 250+ doobie blocks (little concrete blocks with some bailing wire sticking out) to lift my rebar, FOR FREE! 8)  HD wants 42 cents a piece for them   That still wasn't quite enough so I had some broken bricks in a few places.

[DDW_OR]

great find on those dobie blocks
saved over $110

[jmouton]

hey jemclimber i was talking about wire mesh ,  if you put it in then it will be in the middle or so, and most wire mesh you buy is rusted so when you add water it rusts even more , and concrete is porous ,,so do the math ,  it does work good if placed right,,,,,fiber mesh on the other hand was big in the 90 s , has kinda went by the wayside,,,people still use it whether its fiber or metal,   not many in mich,  fiber mesh will crack more than with wire mesh in it ,, fiber mesh is more expensive ,

[kensfarm]

I did a slab off the back of the house..  26x21  I did the framing and hired a concrete finisher.  Got the 4000psi..  wire mesh..  and laid some rebar on top of the mesh around the sides and cellar stairwell..  I did 6in thick slab.  The finisher pulled up the mesh as it was being poured.  He offered to make cuts but I didn't want them.  6 years later.. no cracks.  The finisher had done concrete work for 30 years.. he only wanted $250.. but he stayed all day... directed the pour.. and did the finishing in 3 steps as it dried.  I gave him $300.. he knew what he was doing.
Also had the electric meter moved.   

 

As the project progressed.. old timbers from collapsed bank barn across the street.

 



 

[Weekend_Sawyer]

I have poured 2 slabs for sawmills. Never got around to building a roof over either of them.
What I learned.
Use grade stakes made out of steel to show the middle of the pad so you don't make the middle a                       low spot.

4" is pleanty thick. I dove my skid steer on both of them.

Use concrete reinforcing wire.

Do not trowel it into a mirror finish. Float it and then take a 2' wide broom and brush it. The first one I did had a nice slick finish on it. and when it got wet it was REAL slick!

Have it fall to one side, 1" over 8' is pleanty, this will help water shed off.

Neither of my pad's cracked but the ground they are on was well compacted by cars and trucks over the years driving over it.

That's all I can think of for now.
Jon

[OffGrid973]

Final Plan:
2x6 form surrounding the 4x14x6" thick with lots of stakes to support outside.  (reason=1.03 yards)
$150 for delivery
$125 for a yard of 4,500 lbs from a local place here in Bridgewater, NJ ( shortloadconcretellc )

Told me to call 2 days in advance and I am finalizing the forms this weekend. 
Going to dig down further and lay a little more rock so driveway is parallel to the 6" slab top when poured.

For anchoring the rails down to concrete do I actually want to place bolts into the concrete.   WEDGE ANCHORS? TAPCON? NOT NEEDED?
I am sort of afraid this will lead to more cracking by introducing weakness right off the start?

Anything else I missed?

Comments appreciated,
-Chris

[grouch]

Put in anchor bolts. Not hex-head bolts. Anchor bolts -- L-shaped. You're not weakening the concrete, else every pre-engineered steel building and a world of pole barns should collapse any second now.

Weekend_Sawyer has given you fair warning about a slick finish. My late father-in-law (roofer, carpenter, farmer) poured a porch and hand trowled it to as fine a finish as I've ever seen on concrete. Then he sealed it. After the first rain, he decided it needed a roof and some indoor-outdoor carpet.

[OffGrid973]

Lol...I found a local guy to float it for me after poured and put the rough finish with a broom.

Thanks again forum, pics should be up in the Next few days.

[OffGrid973]

Update: 2x8 are level going to keep em out along with gravel until pour day.



  

 

[Kingcha]

One thing i learn here.   You will want to raise your mill up off the concrete pad at least a foot or more.  You can make your own beams to do it if you want with some treated lumber on the bottom.    It will save your back.  I only went about 8" do to height of my mill roof.   I wish I had gone more.



 


 
Matt

[petefrom bearswamp]

My 2 cents
My slab was poured in 2000
Modified Alaska slab, 12' wide, 26 long.
Footers 12" deep below bottom of floor, 18" wide with 4 runs of re rod in them.
Main floor 6" 3000 pound mix with re mesh.
My climate is pretty darn cold and it has neither cracked or moved.
Maybe over engineered but well worth the effort.
Of course this was for an lt40 not a much lighter mill

[JD Picket]

I would only use fiber added to the concrete for what you have. Wire mesh is a pain and on all government regulated building sites the new standard is fiber and not mesh. I have a 30'x40' shop and the concrete only has fiber in it and I have no cracks but I also have joints cut every 10'. Fiber runs about $9 more per yard and you can't buy mesh for that price. As far as anchors I would use wedge anchors and don't mount the mill directly on top of the slab. It will rust the bottom of the frame at a faster rate then normal because of the chemicals in concrete. You will want rubber between the frame and concrete. Mills viberate and will bust out any anchors you put in the slab. Also the frame will expand and contract at a different rate than concrete. Hope this all makes sense. Just got off working nights.

[OffGrid973]

Makes perfect sense to me, and the vibration was my main concern causing cracks, etc.  Rubber is an interesting idea, just need to find the sweet spot so I don't cause waves in the rails based on where the logs are placed.

[grouch]

My assumption when recommending anchor bolts was that there would be wood or some other cushioning, forgiving material between concrete and mill frame. Bolting the mill directly to the concrete doesn't sound sound (Tom) to me. Bolting what amounts to sill plates (wooden) to the concrete and then building on them (e.g., see Kingcha's post above) lets you take advantage of the stability of the concrete while protecting it from the vibration, different rate of expansion and contraction between concrete and steel, and lets you put it at the height you choose.

[OffGrid973]

Oh man, who knew how heavy rock was. The slate under the dirt that had to be sledge hammered out was quite possibly the most ridiculous necessity I have come across in this project.  Looking forward to the pour on Tuesday morning.

How long should you let a new cement pour harden (days) until I throw the lt-10 and a 1,500 lbs log on there?

 

[Ljohnsaw]

Wait at least a week.  Also, keep the concrete wet after it gets hard.  It needs water to cure.

[Blaszer]

After you've finished the concrete, put burlap over the whole thing and wet it....and keep sprinklers on it to keep it wet.....This keeps it cool and allows it to cure uniformly and reduce chance of cracks....

[OffGrid973]

Thanks for the pointers guys, pour went great and setting up nicely.



  

  

 

[BigZ La]

After you've finished the concrete, put burlap over the whole thing and wet it....and keep sprinklers on it to keep it wet.....This keeps it cool and allows it to cure uniformly and reduce chance of cracks....

10 day cure makes it very hard.

[paul case]

I have never before seen a 1 ton truck mixer like that. Around here if you order 1/2 a yard or 100 it comes in a semi truck sized mixer.

PC

[Ljohnsaw]

Out here, you can get a cart (trailer) with tandem axles and a mixer on it that looks just like the drum on that truck.  It will hold a little over a yard, has a gas motor running a hydraulic pump.  The drum rotation and dump are hydraulic.

[47sawdust]

That is a nice redi-mix truck.Nothing like that here,same as Paul Case mentioned.

I'm surprised your allowed to set up your mill in that neighborhood.I would think the zoning regs. wouldn't permit it.Good luck to you,I'm sure you will get a lot of positive attention.

[thecfarm]

Now that's a cement truck. Smaller,lighter,go across a lawn with less damage too.

[petefrom bearswamp]

Your pad looks good.
I  second the opinion of rubber between the mill and concrete.
I use old pieces of truck bed mat.
I sometimes load big logs on the mill directly with my tractor and the mill still moves somewhat.
If it was steel to concrete I think there would be much more movement as well as vibration stress..

[ChugiakTinkerer]

Old conveyor belt material would work good too.  Would love to get my hands on some but it's like hen's teeth up here.  I do love that cement truck, the right tool for the job.