Laying a smooth concrete floor

[OwlHoot]

Having bought a large ex pub-hotel in Devon, I now have the challenge of renovating a large function room, about 100 by 40 feet, and am quaking at the likely expense of having this done professionally!

I have ripped down several partition walls which the previous owners installed (with the aim of making it a self-contained dwelling, but their retrospective planning application was refused!)

The existing wooden floorboards, some of which are rotten, now need removing and that will leave the concrete underneath.

I then planned to hire a concrete floor grinder to prepare the surface [ https://www.buyfloorpaint.co.uk/surfacepreparation.html ], after which I can paint it with damp-proof sealant [ Wickes Bitumen Based Damp Proof Membrame Liquid or G4 Damp Seal.

But my big problem is not knowing the materials and technique needed for the final stage, which is to lay a smooth concrete floor.

Anyone tried this, or know of a good online DIY reference that covers the steps, in particular how to keep the whole floor level and with consistent satisfactory texture to then lay overlay and a carpet?

TIA

[TheFaQQer]

Depending on the size of the room and what you are planning to use it for, I'd consider a polished concrete floor done by a professional.

When we were looking to do the church, that's the route we were going to take for the main body of the church, because it's that much cheaper for a big room, and you can get some really nice effects. It also works well with underfloor heating if you are going that route (which we were).

Have a look at somewhere like Polished Concrete - SKIM COAT LTD for examples before you dismiss the idea

[anonymouse]

Another way..

DIY Concrete Self-Leveling Floor | eHow

Rather than grind the floor, so long as the lumps and bumps aren't too bad. Then sweep the floor, clean the floor, PVA twice (different water / glue ratios). Mix self level compund, then pour. Video attached.

[northernladuk]

Depending on the size of the room and what you are planning to use it for, I'd consider a polished concrete floor done by a professional.

When we were looking to do the church, that's the route we were going to take for the main body of the church, because it's that much cheaper for a big room, and you can get some really nice effects. It also works well with underfloor heating if you are going that route (which we were).

Have a look at somewhere like Polished Concrete - SKIM COAT LTD for examples before you dismiss the idea

This!! I wouldn't even dream of doing it myself. Get it wrong and you are stuck with it forever. To me it's like plastering. Anyone can throw plaster on a wall but to get a perfect finish is a bit of an art. Tinker with everything else but getting a good floor as a base I would leave to a pro. Am sure it will be expensive but **** it up and it's going to be a thorn in your side forever IMO.

[northernladuk]

DIY Concrete Self-Leveling Floor | eHow

Rather than grind the floor, so long as the lumps and bumps aren't too bad. Then sweep the floor, clean the floor, PVA twice (different water / glue ratios). Mix self level compund, then pour. Video attached.

I tried using this stuff to level an uneven floor and it was a nightmare. Am sure the video makes it look easy but it wasn't. It was this experience that lead to my recommendation above about getting a pro in.

[SimonMac]

When we did a similar size room here in Spain, the key was to build up some form to section it off into smaller areas rather than one big hit, will you be mixing your own concrete or getting a delivery? If doing it yourself make it a but wetter so you can scrim it flat and then keep throwing water over it to keep it damp as it dries to prevent cracking.

We used the added technique of throwing all the excess beer cans under the cement to hide the evidence too!

[Uncle Albert]

+1 on getting someone else to do it. We had to have a large area done to level out a new extension. At the deepest point the concrete is 8 inches thick. That's now been topped with parquet floor which looks great.

The only downside was having to wait months for the concrete to be dry enough for the parquet to be laid.

[vetran]

If you are thinking of the final surface being concrete then get a professional in.

If not and you are mixing yourself as someone says build it up in sections. you can only mix a few tons a day (5-10 with 3 people) manually/in a normal mixer.

If its being delivered get a few mates to lay, then pay a couple of guys to level & polish last layer.

make sure you get the damp proofing right.

[OwlHoot]

I wouldn't even dream of doing it myself. Get it wrong and you are stuck with it forever. To me it's like plastering. ...

Yes, I had a feeling concreting a large floor would be like plastering, in that there was a real knack to it which a newbie with the best will in the world simply wouldn't have.

But then I thought it might not be exactly the same, as there may be some technique like using very liquid concrete that would find its own level naturally without needing a practiced eye and hands!

But one still has the task of setting the wooden (?) "dividers" exactly level, and if the concrete was too liquid it would seep under the bottom of these like water from the base of a breached dam!

I think it is the large area that makes this unsuitable for a DIY approach though, as it can't be done all it once. Shame, because I could save two or three (or maybe several!) grand if I did, and who's to say even a builder might not balls it up?!

[OwlHoot]

Some great replies already - Many thanks guys!

I anticipated the "do it in sections" tip, but my main worry (as mentioned in the previous post) is how to get the dividers exactly level and water-tight (or at least concrete-tight) at the bottom.

Luckily, I don't think the new concrete will need to be 8" thick - An inch layer over the existing concrete and damp seal should be fine.