Advice On Concrete Floor

[need4speed]

After having the ground at front of house levelled and a new driveway done, the drive is about 2" higher than existing concrete garage floor.

As some of the garage floor is damaged I thought I would just re-concrete it and bring it up level.

Ive never done any concrete/cement work before. Can anyone run me through the steps of what I need to do.

Floor is approx 6m x 3m.

 

[Stellaghost]

Obviously the first step is to remove your existing concrete floor, if yours is damaged it may be an indication that it is not very thick and quite possibly no reinforcing present, you will then need to look at the condition of the ground below the concrete and that may involve removing material and adding some hardcore, even if it looks ok I would still be hiring a whacker plate to compress it before pouring new concrete on top. I would also add some reinforcing this will assist in preventing the floor cracking in the future, for the concreting you could do it yourself with a mixer and materials, alternatively you can get someone to do it for you, if you do it yourself, you can purchase concrete mix just water to add, if you do this then build up the concrete and float it as you go so you are left with a smooth floor ( I would try and do this in one pour so an early start ) ready for paint, obviously it will need time to dry before paint is added I'm sure others will chip in with advice a few forum members have done this in recent months regards Stephen

[Simon_CSK]

The first question I would ask is what is the damage and where is it? Then how much height is above the floor to the roof members? Is the floor dry or damp?

These questions would determine how much remedial work you need to do and what you can do. A good base is 150mm concrete with a 252 mesh through it to reinforse it If the existing base is breaking up then as Stephen says, it shouls prpbab;y come up or is it is just a small area break it out and bring back to level with fresh concrete. 

The spec I have given should span over small areas of damage but it is better to cut it out and repair. 

If the floor is damp it would be best to add a DPM

If you cannot afford to loose the height then you do need to remove the old floor. If replacing the floor you need 150mm well compacted hardcore, 50mm sand visquwwn 1000g DPM and then 150mm concrete. 

I am an Architect and domestic Architecture is what I specialise in, this is general info so please feel free to ask specific questions.

[need4speed]

There are no splits in the existing to make me think there is a structural problem. Just a little bit of crumbly surface damage here and there the width of a teaplate. 

Certainly nothing worth pulling it up for.  I really don’t want to do that.

Im not concerned about losing height but can’t go higher than approx 50-60mm or it would be higher than drain channel.

Simon I’ve just seen your location. I’m in Southcraigs, Kilmarnock!

[Blanco]

The problem is that 50 to 60mm is a really awkward height, minimum stable thickness for ordinary concrete is traditionally considered to be 75mm. Also looks as if your floor is painted which means you have no chance of a screed adhering.

If its just a garage and no heavy use is envisaged, see if you can hire a concrete planer/scrabbler and get down that extra inch or two, it'll be a horrible task but it will then give you a good surface to put the screed on. You only really need to deal with the first meter or two  from the door because you will need gentle slope into the drain anyway, for the bulk of the area you just need to get the paint off and deal with the flaky bits.

But as above the proper solution is to rip it out and set the FFL based on the drain.

[need4speed]

Hmmm. The more I’m learning, the more I’m thinking I should just in-fill the low area at door to eliminate the trip hazard.

It never occurred to me that 50mm would be an awkward height but after having it explained it makes sense.

[SPendrey]

3 minutes ago, need4speed said:

Hmmm. The more I’m learning, the more I’m thinking I should just in-fill the low area at door to eliminate the trip hazard.

The issue here by just filling in that area, presumably with a slope, will be a weak thin repair.  You'd need to dig deeper first to ensure the thickness of the material you lay (or pour) is a couple of inches at least to maintain integrity.

[need4speed]

I was hoping to get away with digging further down. Baring in mind that this garage just sees foot traffic. No vehicles in this one.

[SPendrey]

If it is just foot traffic, consider a wooden slope (treated to make sure it isn't slippery), or perhaps a hard rubber one (if you can find something like that?).

[L19MUD]

1 hour ago, need4speed said:

I was hoping to get away with digging further down. Baring in mind that this garage just sees foot traffic. No vehicles in this one.

I would just dig down in the areas you already have partially removed so that you have at least 100 at the most shallow point and then concrete yourself a slope down to the garage floor assuming a slope that steep for a short section is acceptable for the use you have for it.

 

My only concern with doing it this way is water running into the garage, I know you have that ALKO drain directly in front but I have had issues in the past with water hitting the door and tracking under it/being blown under it by the wind. In your case if that happens it will not run back out as the level is lower. When fitting garage or roller doors we normally fix some 70x5mm flat bar on the ground with a suitable sealant just behind the door when closed to stop the water tracking in this way.

[zardos]

2 hours ago, SPendrey said:

If it is just foot traffic, consider a wooden slope (treated to make sure it isn't slippery), or perhaps a hard rubber one (if you can find something like that?).

Or self lay cold tarmac to infill, which is available from DIY and builders merchants.

[Blanco]

If it's just foot traffic then batten and timber the whole floor?

[need4speed]

18 minutes ago, Blanco said:

If it's just foot traffic then batten and timber the whole floor?

Thats an idea I hadn’t thought of. Might even be a little more aesthetically pleasing.

Brings a few other questions though. What would be the best timber to use for this? And how do I attach the battens to existing concrete? Normal rawl type fixings?

[Blanco]

If you are confident there is a damp proof membrane then good quality red wood battens would be pretty durable. Maybe bed them on pitch and screw them down (with rawlplugs). I see a lot of masonry screws around which claim not to need plugs but I don't rate them at all. Batten spacing depends on the choice of flooring, 18mm chipboard flooring can be pretty flimsy, sterling board is stiffer but would need lino over it as wear areas tend to shed or snag. Ply or nice boards? it just depends on budget.

[monkie]

If it were mine I would be tempted to tile it. Very durable finish and easy to clean with a mop or even pressure washer. 

[cackshifter]

If you put wood down, you will have to ventilate the space under, even if there is a DPC unless you live somewhere tropical, otherwise you can expect some sort of rot  issue down the line, there is bound to be condensation etc occuring. Going back to the original, if the door closes over the ALko drain you could let the concrete be higher inside - I have a step of about 1" in the concrete at the entrance to my garage to prevent wind-blown rain getting in.

[Ed Poore]

You can get away with "basically" screeding it to bring the whole floor up to the right height.

Hopefully you can read through this thread over on mig-welding - almost this exact question was asked just a few days ago. Specifically look at Bob's response in post 8: https://www.mig-welding.co.uk/forum/threads/screeding-a-concrete-floor.109349/#post-1761039. I've been to Bob's yard and that floor takes some serious abuse, the man cave he's referring to has a 6 tonne two poster in it with a 101 currently resident. There's an engine dyno, more tool cabinets than you can shake a stick at, heaters, some heavy duty workbenches (aside from the general purpose ones on top of the cabinets from McLaren).

So I would say that you can do the same approach if it's just going to be foot traffic.

[need4speed]

Thanks guys. I certainly have plenty of food for thought now.

[Simon_CSK]

9 hours ago, need4speed said:

Simon I’ve just seen your location. I’m in Southcraigs, Kilmarnock!

I am in Coalhall and everyone round about knows my house

Would you like me to have a look at it LOL

[Snagger]

If the grate is 50mm above the existing floor, and 75mm is a better depth for a layer in strength terms, then as long as you have the head room, I’d go for 75mm - I’d want the floor to be a fair bit above that grate with a slope for the first 6-12” of the floor to make sure any water running down the driveway or rain entering through the door runs down into the drain, not back into the garage.

[need4speed]

1 hour ago, Simon_CSK said:

I am in Coalhall and everyone round about knows my house

Would you like me to have a look at it LOL

That would be awesome Simon. I’m home every Tuesday and Sunday so just whenever suits you. No big rush.

I’ll PM my mobile number and you can’t ping me a text whenever suits.

[landroversforever]

3 hours ago, Blanco said:

If you are confident there is a damp proof membrane then good quality red wood battens would be pretty durable. Maybe bed them on pitch and screw them down (with rawlplugs). I see a lot of masonry screws around which claim not to need plugs but I don't rate them at all. Batten spacing depends on the choice of flooring, 18mm chipboard flooring can be pretty flimsy, sterling board is stiffer but would need lino over it as wear areas tend to shed or snag. Ply or nice boards? it just depends on budget.

Proper concrete screws are great, you've just got to be careful about the hole size. Not too big, or too heavy handed and make the holes too big.

[Blanco]

11 hours ago, landroversforever said:

Proper concrete screws are great, you've just got to be careful about the hole size. Not too big, or too heavy handed and make the holes too big.

OK I'll re-phrase.... we are asked for advice remotely, for an application that is underfloor where remedial action wouldn't be easy, on a substrate of unknown qualities installed with unknown resources, I think concrete screws have sufficient potential drawbacks not to recommend them. I think rawlplugs offer a much surer and safer bet

[Ed Poore]

I'd echo that sentiment, I've yet to get a concrete screw to anchor properly in anything from stone to C40 concrete. At the moment the only thing they've been anchored to is the bucket they're stored in.

Yeah maybe it you get perfect conditions they're great but I've always found rawl plugs, resin or expanding bolts to be easier and far more forgiving.

[Troll Hunter]

My shop floor was "over engineered" with a full area mesh of 10mm rebar on "I can't remember the mesh", but it was a 4" concrete layer.  The installed slope was 1%.

Today I only want my truck in the shop, but tomorrow .......?  Hence my decision for what I have. 

If you can, go bigger, go wider, go longer, go deeper.  Then, you can concentrate on getting more "stuff" (man toys) to fill the space!

Mike