Base for a new machine shop aka "shed"!

Paul

If concrete is making your glass eye water then try old railway sleepers.They must be ex railway sleepers and not the sleepers sold for gardens as they do not have the creosote pressure treatment.Level your site and cover with 2" of sand, bed your sleepers on this.If putting heavy machines in bed ,them side by side and space them out to 2ft centres elsewhere. Lay a sheet of 9mm ply over the sleepers and 4" joists on top,insulate with Celotex boards or Kingspan with 3/4" ply on top.Then tack 12" dpc under the studs and cover the sides and ends of the floor joists.

use 100mm cls timber from the builders merchants this is cheaper than rough sawn with 6"rough sawn feather edge boarding to cover,not shiplap .Apply knotting to all knots and paint with masonry paint straight onto unprimed wood,it lasts for years.

Francis Boyle

Paul

Dig out the base put in 4" of hard core then 2" of sand then put a layer of Kingspan or similar 2" of concrete just before its goes off mix up some cement and skim the surface called blinding, when completely dry paint over with a Latex wash. No damp from under floor insulation will keep your feet warm and Latex will seal the concrete and oil will wipe off.

Regards

Stan

Paul

Some interesting comments from the members. The MPA (hardness) of the mix is a critical consideration. MPA 25 to MPA 32 as mentioned previously is very good advice, especially if any of your work has the potential to cause vibration through the machine to the floor. A durable slab requires good drainage and proper reinforcement. Crushed stone 0 to 3/4" well compacted using a rented or borrowed compactor does a super job in this regard. The concrete can be poured directly on top of the stone. An electric concrete vibrator is handy for ensuring that the mix, especially a higher MPA mix, completely encompasses the reinforcing mesh. You can buy little pillars quite reasonably to set your mesh on to keep it off the substrate thereby ensuring that it is completely encapsulated by the concrete. A slab 4 to 6" in depth should be adequate for your needs, bearing in mind that any potential vibration will have to be controlled by some means. I use hard rubber ice hockey pucks under my lathes. Now, the most important aspect in making your slab durable and free from cracks is a full and proper cure. My rule of thumb here in eastern Canada (Lat N 46 Deg) is a 24 day cure for MPA 25 and a 30 day cure for MPA 32 before any significant weight is placed upon it. During the entire cure, keep the slab lightly moist using a garden sprayer and water and keep it covered with a poly sheet to slow the evaporation. This is especially important if the area is exposed to direct sunlight and hot air temperatures. It is a nuisance job but the results are well worth the effort. Finally, there are some excellent concrete sealers available that you can apply with a roller, brush or garden sprayer that will help make the floor resistant to oil and dusting. If you wish to paint the floor, ensure that your selection of sealers will accept paint. To paint new concrete floors I personally forgo the sealer and apply a two-part epoxy finish. The epoxy process requires excellent ventilation and as a minimum, the use of a properly fitted P90 respirator not to mention nitrile gloves. Good Luck.

Bill

Investigate the cost of hiring a "power floater' for concrete floors . For those that don't know this is a machine with blades that are rotated to give a very smooth flat finish to the concrete. You have to wait until the concrete has gone off enough that you can walk on it and use the power floater - which could mean waiting until the middle of the night if you have a pour late in the day - but not gone off too much that the 'fat' in the concrete can't rise up to the surface to be smoothed off. The surface finish is very smooth if done well, but be careful that it is not too smooth that it becomes very slippy when wet!

Chris

Few questions arise from Bill's post, not necessarily directed at him.

What is MPA 25 in amateur terms ie bags of cemont per cubic yard of aggregate?
How much free water is left in concrete after say the 24 days that is still going to come out and cause rust?
After keeping it wet during the curing stage how soon before it would be ok to put a dehumidifier on to protect the contents?
How long before the sealer can be applied as presumably the residual moisture would be trapped or cause some problem with the sealer adhesion?

Paul

I come from a long line of English and Irish stone masons and concrete finishers so I have picked up a little knowledge and experience over the years. I did not take up either trade but rather opted for becoming a sign painter; in the days when we hand lettered signs with brushes, quills and stripers. I digress. At the risk of being too long-winded for some members who do not appreciate quality English composition, I offer the following.

Unless the floor area is extremely small, I strongly recommend that you do the preparation yourself but purchase your concrete premixed. This allows for a quick and steady pour and eliminates the risk of unplanned interruptions such as equipment failure, calls to nature etc; not to mention nosey neighbors. You can tell the company the strength of the mix that you want (eg MPA 32) and you need not calculate the required amount; the company will do that for you if you provide them with the dimensions. If you haven't done this work before, I also recommend that you engage a local concrete finisher who will have all the necessary tools and equipment to do the job quickly and properly. Start to finish, the pour should not take long. The finisher will probably need to leave after the pour and initial trowel is complete and return a bit later (depending on the weather and temperature) for the final finish trowel. You will be busy enough wheeling the concrete unless the truck can get close enough to pour directly on the floor using the chute. If at all possible all equipment should be removed from the work area until the floor is completely finished, cured, sealed and painted. While the floor is curing as per my previous thread, the area should be ventilated to allow excess moisture to dissipate. Whereas you intend to pour inside an existing structure it is prudent to apply poly 3 to 4 feet up the walls to catch the inevitable splatter from the pour.

You can set up a dehumidifier any time after the slab is hard enough to walk on; bearing in mind that the slab should still be kept moist and covered in poly. Despite having a warm and dry 24 X 24 workshop in my basement, I have a dehumidifier in my shop set at about half-throttle year round and have absolutely no problems with rust even during the most humid weather.

I am enclosing a few links that explain the terminology and the technology of concrete work.

**LINK**

**LINK**

**LINK**

**LINK**

**LINK**

Wee Willie Winkle must now go tinkle.

Cheers

Thanks for all the info Bill and everyone

Had a friend who is a QS come round to give some advce on the structure and he also suggested that by the time I have faffed about trying to implement alternatives it will be quicker and no more expensive to get a truck load of pre mix in.

So, plan is to hardcore, 50mm sand blind, dpc, kingspan then 150mm C30 with mesh. May run it a bit thinner in the store and woodwork parts of the shed to keep it to 1 load.

Hopefully get this sorted in the next 4 weeks so will let you know how I get on!

Cheers,

Paul.