Garage floor levelling

[DIY-Si]

As part of my garage refurbishment and workshop prep, I wanted to level and smooth the floor. For the most part, the floor was already relatively smooth but it has plenty of small divots and runs out in places. There is also a roughly 2.5" step about 2m in from the back from where the floor has been extended in the past, and who ever did the extending did a poor job of keeping it level with the existing slab so there's a rise in the middle and a big drop to the door at the back. The slab is made of up of 5 separate pieces, and there's a manhole cover in the back section too.

 

For the previous owners, it was just a garage and the uneven floor didn't matter. But rolling engine cranes and the like around would become a right pain over time. So I decided to bite the bullet and level the floor. Following some drainage work needed for a new ensuite, there was a massive hole to fill with concrete. This was done at a depth of 400mm, which is huge overkill, so that I could have a 2 post ramp in the future. This has now had 8 weeks to dry out, and whilst not fully dry it is dry enough to make a start. Having dug the floor out, I also know that there's no DPM under the floor. Thankfully, the floor is in generally good condition, not cracked or dusty and so its pretty much ready to go.

 

Since there's no DPM under the floor we dug out, I've had to assume there isn't one anywhere under the floor. As such, the first step needs to be putting a DPM down. There are a few way of doing this, and following quite a bit if research I decided to use some of the UltraFloor products from Instarmac. They do an epoxy paintable DPM that I've used before. You mix the tubs, pour it on the floor and roll it about a bit. Once that's down and cured, I'll be using their Base layer product to take out the worst of the dips and runs. 24 hours later, I can pour a layer of HD Top, which is a wearable fork truck rated layer. This stuff is expensive at £25 a bag, but worth it. The Base is there to take out the worst of the rear section of the floor first. The front larger bit will just need the HD Top layer.

 

Today was put aside for doing the DPM layer, and I had ordered what should've been enough to put two thin layers down. The prep was straight forward, just needing the floor sweeping twice and then hoovering. I have a trusty garage hoover that gets regularly abused for things like this! This is also not a job to attempt by yourself for a double garage, as the epoxy has a pot of life of roughly 45 mins. As such, my fiancée was roped into helping. I reckon a single garage could be achieved solo on a warm day, but it would still be tough going.

 

Once we started working, it became apparent that the stuff was just going down thicker and thicker as we went. I suspect it was a little too cold for it to flow properly and we ended up using three of the four tubs to cover nearly all of the floor. However, due to the thickness of the covering, we won't be doing a second layer as it won't be needed. The rear section of concrete was much, much bumpier than I realised and we couldn't roller the epoxy on at all, instead having to scrub it in with a 2" brush. This was very slow work, and the temperature was dropping too quickly now it was dark to allow the epoxy to flow so we stopped just shy of the end and left the fourth tub to finish off tomorrow and cover the back of the garage floor again. We could've carried on and finished, but I wasn't willing to open a £50 pot of epoxy to do the tiny section that's left. Instead, I will start again in the corner that's missing the epoxy and recover the whole of the lower rear section.

 

More to follow as the steps are done! Any questions, or suggestions, please fire away.

[Rich201060]

14 hours ago, DIY-Si said:

More to follow as the steps are done! Any questions, or suggestions, please fire away.

A few years ago I nocked our kitchen into the back of the garage and had a similar issue. My brother is in the building trade and he recomended a dry screed, basically I mixed it and he levelled it, then I put the self leveling stuff down and tiled on top. Looking at yours you would have to raise the manhole then perhaps run some batons round at the same height, fill it with a screed mix and level off they recon 25mm is minimum for a screed. Im not sure however if it will stick to your DPM. 

[DIY-Si]

I did briefly consider a screed, but as you say, the minimum height gain is 25mm and usually more. The self levelling stuff will go down at between 5 and 15mm thick, which is what I'm happy with. The front entrance is currently flat, and I'm keen to maintain that as best I can. A 5mm step won't cause me any grief.

 

The manhole and step between the levels will stay as it is, and be edged with some left over roofing upstand I've got. I'll just use an offcut of ply or similar to maintain the floor level, as the rear section won't see anything like the traffic of the front section.

[Rich201060]

5 hours ago, DIY-Si said:

I did briefly consider a screed, but as you say, the minimum height gain is 25mm and usually more. The self levelling stuff will go down at between 5 and 15mm thick, which is what I'm happy with. The front entrance is currently flat, and I'm keen to maintain that as best I can. A 5mm step won't cause me any grief.

 

The manhole and step between the levels will stay as it is, and be edged with some left over roofing upstand I've got. I'll just use an offcut of ply or similar to maintain the floor level, as the rear section won't see anything like the traffic of the front section.

Sounds like you have it covered (no pun intended) good luck 

[DIY-Si]

@Rich201060, thanks! Having seen another garage floor finishing thread recently that we didn't get to see the end results of, I'm hoping this will show what I've had to do from start to finish.

 

I'm by no means a pro, but I do expect to be able to improve the floor quite a bit over what it was like. Hopefully others will see it, and decide if they can plunge and tackle similar projects themselves. 

[DIY-Si]

Tuesday is my allotted garage evening, so I was able to get the next stage of the floor levelling done. I got up early (and skived off work for a bit) to get the last tub of epoxy DPM down. I started by the back door and worked forward until I ran out of it, which meant that the 4 little rear sections of concrete all got another coat. By doing that step this morning, it had gone off by the time I got home from work, and it was then ready for a coat of primer. It's also worth noting that the DPM does a surprisingly good job of evening out the worst of the small bumps and dips.

 

 

 

The primer is a very simple step, as it's a pink liquid that just needs rolling out over the patch you need to level and part way up the wall to ensure the edges are fully covered. Once dry, it goes translucent, so knowing when it's ready to go is also simple. Due to ordering everything from Travis Perkins in one go, I had to order 6 bags of the base instead of the 4 that I expected to need. Likewise, I ended up with 12 bags of the HD Top vs the 11 I wanted and 4 bottles of primer against the 1 I would need part of. The photo above is pretty much the tools needed to get this going. One thing that needed doing first is to dam the edges of the floor. On one edge is an air vent through to the under floor of the front room, and there's the manhole cover that needs damming too. If not, the compound will find any little hole and start to run away as it's surprisingly watery. As such, the dams were all silicone'd into place.

 

 

With the primer dry, and the dams in place it was time to start mixing up. This needs 30L buckets, as anything smaller just won't work for the 25kg bags. Each bag only requires 4.25L of water, and since the buckets are thin enough to see the water level through (I used plasterer's buckets) they were both measured and filled in the kitchen first to save me time. I chose to use 2 buckets, so I can mix up in one, and use the other purely for fetching water to the garage. Although the water only fills the bottom few inches of the bucket, once the compound is mixed in you end up with something nearer 20L! It's also wise to remember that the bucket now weighs 30Kgs, and pouring it accurately is tricky. Thankfully, accuracy isn't particularly needed, as a trowel is needed to push the compound around. The photo below is just the first bucket.

 

 

As I got going, photos weren't really taken as I was doing this solo, and the working time of the compound is only 20 mins. The floor was also more uneven than I had realised, as I did end up using all 6 of the bags. I could've used just 4.5 bags I reckon, as this is just the Base layer, but I wanted to get a decent covering over the entire area so used all 6. The thinnest section, which is lower left in the below photo is 6-7mm, yet the deepest edge by the door is maybe 30-35mm. I had expected it to be nearer 20mm, hence why I was two bags over or 50% out!

 

 

When viewed from a lower angle, I was quite pleased with how flat the floor looked. I did attempt to use a spiked roller to draw the air bubbles out of the compound, but it only really worked in the thinner sections as the compound was too deep to allow it to roll. Once it has dried I will know how much of an impact, if any, this has had. Even if it does cause a few pinholes, the layer of HD Top will easily cover those up as that will only be 5mm thick and therefore a doddle to roll out properly.

 

 

The next step will be two pour the HD Top on this section, but I suspect that will have to wait until next Tuesday as the floor will need at least 3 days to dry at the thickness I've used.

[dombanks]

Which self levelling stuff are you using? I needed to do this a few yrs back and wasn’t sure that anything I could get was up to the job without breaking up
 

that paint on bitumen damp proof stuff is grim from what I can remember 

[DIY-Si]

@dombanks, I'm using Ultrafloor products from Instarmac as I've used them in the past and my research failed to bring up anything that I considered better. As you say, blackjack/bitumen is a right PITA to use, and wouldn't be any use in this case anyway.

 

The DPM you can see above is purely epoxy. The Base layer is then poured over it, once primed, to take out the worst of things. This is where I'm at now. The next, and penultimate for me as I will be painting it, layer is Level IT Top which is a fork truck rated, wearable top coat. It can be left entirely as poured and used as a finished floor surface. This stuff is good, but not cheap. Even using a trade account, everything came to £600 for the floor, or roughly £20/sqm. And that's with no labour to pay either.

[dombanks]

Cool thanks. I ended up putting down a 2" thick layer of concrete. wish I’d know about that stuff back then. 
 

your doing a cracking job keep up the good work. I am itching to get back into my garage to finish it off. I’ve put an industrial floor coating down from marl coatings but it failed and Dissolves if it gets wet! They were great; tested the batch I had, reckoned it wasn’t quite right and sent me a brand new batch to over coat. Just the garage is full of crap from moving 🤦‍♂️

[DIY-Si]

I wouldn't feel too bad, these are relatively specialised products. Even the technical team at Instarmac have suggested I am overdoing it as they consider this approach to be suitable for industrial applications!

 

If it weren't for us replacing the roof soon after we moved in September, my garage would also be full of stuff. As it is, the imminent arrival of my XI kit has meant that I've got a fairly free pass to hide that stuff all over the house and in her shed, as I know that once it arrives, I'll never get the floor sorted. This way I can do it once and hopefully not have to redo it for at least a decade.

[Jim RS]

You can't beat having a good building products supplier that knows their way round the building site especially as new materials are coming on stream often. It's been a couple of years since I was doing concrete repairs but the general rule was to use modified cement products for structural repairs and if the structure was sound epoxy materials were favorite for there better wear and decorative qualities. As with all things proper preparation is key to a good, long lasting job, then the correct product selection for the work required. Our extreme product choice was Fastplug which was immense and we repaired any concrete with this even roads/runways and it was waterproof, needed no primer(just clean solid concrete), could be applied thinly, set within 30 minutes and could take heavy transport within 1 hour, not cheap but never failed itself, not what could be said of other high specification materials.

[dombanks]

I’d like to report back on this floor paint as on paper it should be indestructible. Putting it down with a deep pile roller was a doddle and it seemed to act like self levelling. I’d say more smooshing it around the floor than rollering! I spoke with the tech guy from the company and he said my prep and application was fine likelihood was the product batch and sent me 10l more. 

[DIY-Si]

@dombanks, any chance of a link or a pointer to what you've used chance? I'm still trying to figure out which one of the many, many epoxy or resin floor coatings/paints to use.

[DIY-Si]

As it's Tuesday, I've been able to get a little more time in the garage to get the next layer done. The Base layer required two coats of primer, one done yesterday and the other this morning before work. Each clat only took 10 mins to do on such a small patch. Before I started, seeing as I had all evening, I put another coat of white on the walls. I may put a third on, I'm not sure yet if it'll be needed. I'll probably do a trial patch and see if I can spot it or not.

 

With the painting done for now, and my kit ready, it was time to stop putting things off and make a start. I expected to only need 2 bags of the HD Top for this, but got three ready just in case. The first bucket went done smoothly, and flowed out fairly well. This stuff will hold a 1/8" edge so it does need towelling about, as its only meant to be 5mm-ish thick.

 

 

 

Soon enough, the second bucket was mixed and poured. This one needed a bit more troweling to make it flow into the first bit evenly, but it seemed to go well.

 

 

I'm pretty pleased with how its gone, and the spiked roller seemed to even the few trowel lines out nicely. Once it had sat for 15 mins or so, a few bubbles started to come to the surface. I fear this is due to me mixing the compound at too high a speed. Most of them were popping easily by themselves, but I'm sure some will remain. Thankfully, they're easy enough to sand flat if there any too many before I paint the floor. The morning will tell!

[dombanks]

On 17/01/2021 at 20:00, DIY-Si said:

@dombanks, any chance of a link or a pointer to what you've used chance? I'm still trying to figure out which one of the many, many epoxy or resin floor coatings/paints to use.

I used aquatuff industrial floor paint from marl coatings. Cracking company to deal with and dead easy stuff to put down. It’s not cheap but not massively expensive either and I’d recommend a chat with them for prep and if you need a sealer first