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Base for a new machine shop aka "shed"!

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Paul Major17/02/2014 22:40:58
53 forum posts
13 photos


just making plans to convert/refurbish part of a shed I have and turn it into a proper area for the growing number of machine tools I seem to be collecting.embarrassed

I am thinking about pouring a concrete base over hardcore, just wondered if there were any recommendations or things to bear in mind when doing this.

Plan is too mount the machines (mill, shaper and lathe) onto the floor either on adjustable feet or shimming and grouting.

Picked up a Wyler clinometer as part of a job lot of items at an auction so figure that should help with the levelling.wink



Bazyle18/02/2014 00:05:18
6379 forum posts
222 photos

Dig deeper and put in 3 in of cellotex if you are thinking of heating it. Else you could think of not insulating the base, insulating the walls of course, so the heat rising up from the earth will keep it just above freezing.
I am always having trouble lifting things over door thresholds. Think about how to avoid more than a small lip and if necessary a gap outside the door if it opens outwards that can be simply filled in by a few planks to make it easy to wheel things in and out.

This is where the poster turns out to be livijng in California and have a shed twice the size of my house but directly over a fault line.

S Deakin18/02/2014 00:21:10
21 forum posts

Hi Paul

Make sure to put a damp proof layer in or a simpler way that also seals the concrete against oil spills is to add PVA in the mix. This leaves a nice glossy floor and when you sweep it out (if ever) you will find it does not become a dust bowl.

_Paul_18/02/2014 00:23:49
543 forum posts
31 photos

The weight and size of the machines will dictate how you construct the base, you don't want to plant a 5 ton DSG lathe on 4" unreinforced concrete.

IMHO for an average "Shed" I would lay 6" of concrete on top of your (well compacted) hardcore and for the extra small cost drop in some reinforcing mesh that way if you buy bigger machines later on you already have something reasonably substantial to stand them on.


John McNamara18/02/2014 02:45:06
1341 forum posts
127 photos

If you have the room think about a sink, or rather an all in one laundry tub, they are fairly cheap to buy. they come in various widths down to 350mm by about 600. Now is the time if your drainage access point is through and under the slab. I don't have one but if and when we move and build a new dream shed it will have one. Maybe even a shower.....Now that is dreaming.


Paul Major18/02/2014 09:57:17
53 forum posts
13 photos

Great replies, thanks guys. laugh

Fortunately the shed is in Kent not California, although we have had our own sink hole recently on the M2smile o

Heaviest item is the Beaver mill, probs about 1250 kg's. Will look into what sort of mesh and concrete to use.

Not thought of putting PVA in the mix, haven't heard of that before. Was going to put a polythene membrane under the concrete before I poured but if PVA would stop it dusting and oil sinking in that would be a bonus as it is a nightmare in my workshop!

Planning on keeping the entrance reasonably low but building a removable low level ramp to aid with shifting stuff. Having seen how useful it is in my workshop also thinking about rigging up a rail/gantry inside for lifting heavy components if I can find some cheap RSJ.

Might think about a sink, means I need to run in water though, hmmmmm,

Keep the thoughts coming!



Bazyle18/02/2014 12:49:59
6379 forum posts
222 photos

One never knows the level of experience of the OP but others reading this might be novices. So for someone that needs to be told to put in a damp proof course also note the topsoil must all go since any soil containing biomatter will eventually decay causing a void. On top of the hardcore you need 2 inches of sand 'blinding' to prevent sharp bits piercing the DPC. Put the reinforcing at 1 in above the bottom of the concrete - make little cement blocks with a twist of wire as spacers (my first ever building site job as a kid).
Consider installing an underfloor heating pipe if you can find a free offcut from an installer. You might never use it but kind of hard to put in later.

John McNamara18/02/2014 15:15:52
1341 forum posts
127 photos

When I poured the slab for my garage/workshop I asked for a steel trowled finish using stone dust and neat cement applied after the slab had been levelled and wood floated (Using a wooden trowel) to push the aggregate down. once it is partly set the contractor could move about on the surface perched on small wooden boards but before the water reabsorbs, the finishing dust cement coat was applied and trowled.

I tried to find a decent link describing the process, Quite simple actually they just mix the stone dust and cement about 50/50 and sprinkle it dry all over the surface of the slab, maybe a mm thick. then get to work polishing the surface with a steel trowel, when done it has a dull shine.

I did not have to instruct him it was pretty standard 25 years ago. The floor is still in very good condition even where I stand at the lathe the concrete is only slightly worn. It creates a very durable surface that is a lot less likely to dust up. You can add cement powder colour also if you like For my slab I used black, you end up with a charcoal colour.

If you are worried about strength instead of 20MPA concrete you can use 25 or even 32MPA concrete. From memory I upped mine to 25. Make sure you don't skimp on mesh the supplier will probably be able to advise if you don't have an engineer. The mesh suppliers will also sell plastic chairs to raise the mesh to the correct height they clip on and are fairly inexpensive, they will also have plastic membrane and duct tape. If it is not wide enough join it with tape.


Edited By John McNamara on 18/02/2014 15:16:31

John Hewes18/02/2014 17:38:24
22 forum posts
2 photos

I have a concrete floor covered with 25mm of Celotex and then plywood about 18mm thick.

The floor is lovely to work on but you need to fix machinery direct to the concrete by long rawlbolts or similar.

Easy to fix things to the floor and warmer than concrete.


Dusty19/02/2014 19:38:22
493 forum posts
9 photos

Tut tut, a shed is where you keep ( or Swmbo) keeps gardening tools. Things like that should never darken a workshops door.

Paul Major19/02/2014 20:27:44
53 forum posts
13 photos

LOL, thanks guys.

My workshop has run out of room for all my kit. We have a large shed subdivided into 4 compartments at the mo that needs re-roofing and some other work. Thinking I can use the shell and "re-purpose" the interior to make a serious 'shop for the machines, but it will still look like a "shed"


charadam20/02/2014 00:33:39
185 forum posts
6 photos

I laid a 5" concrete floor slab over 50mm of Kingspan. Laid quarry tiles over the concrete and waterproof grouted overall.

Once the machinery was through the door, I welded up a door frame of 75 x 30mm box section and installed it with brackets rawlbolted to the structure (so the machines may be removed to pay for my first 2 days of residential care).

This was in 2004 and the Chipmaster lathe and Boxford mill are happy at home.

Ian S C20/02/2014 09:39:46
7468 forum posts
230 photos

Here in NZ the earthquakes over the last 3 years have seen changes in the requirements for concrete floors. Don't quote me on the dimensions. the area gets dug out about 600 mm packed down, I think a layer of black plastic goes next, then gravel, then 200 mm thick foam plastic, with gaps between , reinforcing is layed in the gaps, then the reinforcing mesh is put on top of the foam blocks, on top of plastic cones, then comes the concrete. I'v got a photo on the camera that I'll put in my album soon. Its called raft flooring, underneath there are all these 200 mm ribs with a fair bit of steel. Friend has had to put his workshop on hold until he gets an engineer to design a floor for it, he was just about to start building last year, when the new regs., came in. Ian S C

chris bond 120/02/2014 13:19:09
6 forum posts

Hi Paul, Adding P.V.A. to the mix will not damp proof the concrete, but it will simply "plasticise "it making it nice ar and easier to lay and give a smoother finish, the more you "polish the wet mix the smoother it will be when set, then You should use a good quality floor paint, To add a damp course is simple, after you have compressed the hardcore, blind it with shingle than sand level till smooth then roll out your Visqueen , do not walk on it though then pour and level your concrete which should be about 6 inches thick, and have mesh in it otherwise it will crack.

I have a very sensitive level (it measures in Radons) if I set it on my lathe bed, the bubble will actually move as I approach or back away from the machine. Thus proving that Floors are "live" unless properly constructed! I had to facilitate the fitting up of a very special super speed ticker tape operated circuit board drilling machine in the eighties and the base for that was 3 metres deep,,,, Just for stability!!


Paul Major27/04/2014 22:54:55
53 forum posts
13 photos

Getting closer with his now.

Old shed is stripped out to frame. Has a concrete pad laid around outside and across middle to support the wooden floor joist many of which have rotted out sad.

Was planning to pour a 150mm slab inside the perimeter until I worked out that at 9m x 5m a 150mm slab is near 7 cu m. Then looked at the price of ready mix and fell over.

With that and the osb for walls, kingspan for insulation and box section roofing looking at £2k for a shed angry

Need to find lots of seconds/or used kingspan and roofing. Not sure what to do on floor yet, might just drop in pads for the area the machines are going in.

Thoughts......dont know



Ian S C28/04/2014 11:48:30
7468 forum posts
230 photos

This is the preparation for a house near to my place, this design is the result of changes made after the earth quakes 3 years ago. That is 200 mm thick poly foam.The right hand side is where the workshop would be, that's the garage. dsc00757 (640x480).jpg Ian S C

Bazyle28/04/2014 13:01:17
6379 forum posts
222 photos

One way to reduce the total amount of concrete is to leave a 6 in gap all round the edge. That enebles you to take the wall insulation down to meet the under slab layer and avoid a cold bridge.

Is 6 in really necessary for that weight of machine? I think other threads have suggested 4 in (reinforced of course) is enough.

edit : I'd like you to try the 4 in before I do my shed floor. laugh

Edited By Bazyle on 28/04/2014 13:02:43

John Stevenson28/04/2014 13:43:03
5068 forum posts
3 photos

I think a lot of the replies are just people parroting things they have seen and read.

My workshop floor is 3 to 4" of concrete, no re-enforcing laid on about 12" to 18" of compacted hardcore with about 2" of sand and a PVC liner underneath.

I aimed at 4" but dare say some is only 3" in the odd place just as some will be 5".

I should hate to guess just what is stood on this, the CNC is close to 2 1/2 tonnes, the big TOS was also about 2 tonnes.

There has to be 5 tonnes of metal on the rack at any given time.

Any major machine movements in the shop have to be made to Air Traffic Control at Teddington as we are in the flight path for East Midlands Airport and they need to know so they can recalibrate their compasses.

John McNamara28/04/2014 14:01:48
1341 forum posts
127 photos

Hi Ian S C

The concrete construction method is also called a "waffle pod".


Fairly easy to construct and they use about 20% less concrete, also minimal excavation is needed if the step up to floor level can be accommodated in the design. Excavated material is becoming very expensive to dispose of in big cities.


JA28/04/2014 15:48:58
1401 forum posts
81 photos

Just looked at the plans for my garage extension (workshop) which needed planning permission and building regulations (England). It states: 100mm concrete (trowelled smooth), D.p.m. (1200 gauge polythene), 100mm blind hardcore. I believe that the builder I used followed the plans and the building inspector past the construction. I sealed the floor with floor paint about six months after construction and it has remained in good condition for 18 years. The thought of repainting the floor fills me with dread.


Edited By JA on 28/04/2014 15:50:57

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