Concrete floor or look-a-like?

Having floor boards I'm assuming you don't have a solid floor. The pine with be fixed to wooden joists?? There is a really cheap option. Ply over existing ply and they now do a concrete lookalike in a vinyl.

There’s nothing wrong with JKB’s answer and for an office a ply substrate, feather edged on joins, followed by a quality sheet vinyl glued down would be straightforward, cost effective and would look great. He’s described exactly how you should fit vinyl over timber subfloor so I am absolutely not disagreeing with his answer. I recently installed a Polyflor Polished concrete sheet vinyl so it’s quite relevant and certainly fresh in my mind and it looked great by the way in my customers kitchen. However, I picked up on your point that the room is also a workshop and I’d therefore consider how robust and hardwearing you need the floor to be. For example, if your work/hobby involves moving heavy materials/ machinery on dollies/trollies, maybe dropping tools by accident, laying out timber or metal work material to use the level floor as a workspace, potentially dragging heavy stuff around etc etc, your great looking vinyl could damage/ mark/ rip quite easily. If this is the case you could choose different, more authentic and robust options set out below. Remove the pine floorboards, spend time checking the joists are super rigid and they don’t rock/move at all, insert more timber noggins between the joists to strengthen, potentially even bolt on sister joists to the existing to double the joist width and rigidity using coach bolts. Then glue and screw a 24mm structural plywood to the joists, 10mm expansion gap to perimeter, fill gap with cork strips and flexible silicone. Once you’re happy there is zero movement in the subfloor you can prime the new ply then pour and skim a quality flexible deep fill latex (such as Ardex NA), pour and skim a fibre reinforced levelling compound at 50mm+ thick or even pump in a gypsum based screed. These methods would be considerably more costly than a vinyl option but it will achieve an actual continuous grey mortar based floor that will be plum level, can be hardened, polished, painted and repaired and give you the genuine authenticity. The other benefits of this method are, by removing the pine boards and therefore exposing the joists and void 1) you give yourself the opportunity to thermally insulate the room and 2) you can sell the pine as reclaimed boards and recoup £££ (depending on condition you can get good money, especially for 4m lengths) Clearly the route taken will depend on several factors such as 1) budget 2) how durable the floor needs to be 3) the importance of desire to achieve the look vs the desire to install the real thing 4) the structural implications/suitability (weight of latex covering) 5) the acceptance of raising the floor level by approx 2 inches and finally 6) timeframe, a 16sqm room should be ply sheeted and vinyl fitted in a day potentially, max 2 days if additional prep is required, where as the authentic install would be minimum 1 week plus. I would also offer one more method that is authentic in terms of achieving an actual concrete floor and from a floor fitters perspective is quite straightforward and certainly offers the most robust result while costing somewhere in between the other 2 options discussed; assuming the office/workshop is ground floor and the joists only span this room (i.e. there are no internal walls built on top of the joists), you could potentially remove and discard both the joists and pine boards, lay a roll of DPM and sheets of foam insulation in the void then pour traditional concrete to the level you require, which can be directly machine ground/smoothed, polished or painted to your desired finish. This method would undoubtedly offer the most hardwearing and durable result out of our 3 options together with being quite cost effective but the suitability of this install depends on other factors and could have other implications that increase costs. These factors and implications could be as follows: 1) structurally, as already mentioned regarding the need to be ground floor 2) no internal walls built on joists we want to remove (if so we’d need to set foundations and dwarf walls underneath to support which would be expensive and ridiculous 3) additional £££ due to potential location of utilities such as plumbing/radiator pipes, wiring, drain covers and water stop cocks etc that might need relocating or updating for suitability with concrete submerge and reduced accessibility. There are great benefits though aswell; 1) option to thermally insulate (advised) 2) super durable that will last forever 3) will withstand any weight 4) can pour new concrete floor to exact same level as adjacent rooms for a nice transition (hallway or corridor for example) 5) straightforward install from floor fitter perspective 6) not super time consuming assuming all goes to plan 7) offers ‘finish’ options, such as quantity and/or type and colour of ballast clippings/gravel 8) cost effective solution that won’t break the bank and will only ever need maintaining (re-polish) but never replaced (like a vinyl for example). I haven’t lost sight of the original question which was requesting straightforward or alternative options. I’m guessing you wanted ideas for the least invasive and stressful install; the fact is the type of flooring and look you wish to achieve can be really quite specialist, if done properly, and whilst there are always cheaper or quicker and simpler solutions & alternatives to projects/installs to achieve the desired end result, the choice you make will always depend on the factors I mentioned such as your budget, which could quite rightly be the major influence and critical decision maker, but in my experience where budget is not critical and can be flexible, the most important thing is the expectation. Manage your expectations so you’re happy with the look and end result. For example, ignoring budget restraints, if someone admires and desires distressed, rustic, knotted, real oak flooring, they should go for that rather than pick a cheaper laminate that looks like it. If we really like real slate tiles we should choose those over an imitation LVT. Put simply; fulfilment, satisfaction and achieved expectation should be the significant factors when one has a vision and is passionate about it. I hope you can tell I’m passionate about my trade and whilst I hope this has been helpful I regret if I have confused anyone reading due to info overload or potential contradiction. I do have a tendency to be thorough and cover all bases. Have a great Christmas!

Hi Install 8mm marine ply (exterior ply) throughout. Seal and feather all joints of new sub floor and finally apply finish floor covering. 1 method: The new ply floor once fixed into position will be primed with an epoxy (scratch coat microns) then you apply another tight coat of epoxy but this time cast flake (or a pigmented aggrogate) in to the epoxy and let it set. Next you brush the excess flake and remove entirely any loose flakes. Once you have removed all excess flake (or coloured aggrogate) you then need to de-nib and lightly key (create abrasion) the surface making sure there are no blemishes or nibs remaining throughout. Finally you seal the floor with a clear epoxy. You will now have a decorative, hard wearing, seamless, chemical and water resistant floor with a gloss finish. And you could, more than likely choose a colour that matches your room.