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Garage floor levelling


DIY-Si

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So morning has come, and the compound has cured. However, the bubbles haven't all gone away. Every one of the white dots in the photo below has a black pinhole at its centre. As they started to appear 15-20 mins after the pour, the verdict is that the priming coats were insufficient or applied too thinly. As the wet compound hits the floor, the water starts to suck into the base layer, releasing tiny air bubbles. These are what then floats to the surface of the compound to dry as pinholes.

 

 

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Thankfully most of them have popped, leaving the pinholes and very few bumps. Whilst annoying, it is a mainly aesthetic problem and shouldn't happen at all on the bigger section of the floor as there's only the impervious DPM there which has no air to release. Any air in the mix will be dealt with by the spiked roller.

 

The bumps can be easily sanded flat, which will reveal more pinholes, but the holes will then probably all need some sort of filler to prevent them showing through what ever paint I end up using. So its a bit of a PITA, but nothing that can't be fixed.

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2 hours ago, DIY-Si said:

So morning has come, and the compound has cured. However, the bubbles haven't all gone away. Every one of the white dots in the photo below has a black pinhole at its centre. As they started to appear 15-20 mins after the pour, the verdict is that the priming coats were insufficient or applied too thinly. As the wet compound hits the floor, the water starts to suck into the base layer, releasing tiny air bubbles. These are what then floats to the surface of the compound to dry as pinholes.

 

 

20210120_075248.thumb.jpg.4cb018004a0af99a56293a5a551e4575.jpg

 

Thankfully most of them have popped, leaving the pinholes and very few bumps. Whilst annoying, it is a mainly aesthetic problem and shouldn't happen at all on the bigger section of the floor as there's only the impervious DPM there which has no air to release. Any air in the mix will be dealt with by the spiked roller.

 

The bumps can be easily sanded flat, which will reveal more pinholes, but the holes will then probably all need some sort of filler to prevent them showing through what ever paint I end up using. So its a bit of a PITA, but nothing that can't be fixed.

 

When I levelled my garage floor last summer I got the same result. I used a course faced house brick to rub the area surrounding the pin hole flat. If you are painting the floor it will be fine. In my case I used interlocking garage floor tiles so wasnt too bothered about pin holes

 

John

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I like the house brick idea. I was going to abuse my little B&D mouse, but a brick is probably easier given how few lumps there are.

 

Did your paint show up any of the pinholes at all, or did it cover them all?

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45 minutes ago, DIY-Si said:

I like the house brick idea. I was going to abuse my little B&D mouse, but a brick is probably easier given how few lumps there are.

 

Did your paint show up any of the pinholes at all, or did it cover them all?

I didnt paint. I used floor tiles

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A light sand over will remove the top of the bubbles and smooth down the edges as it is new and still relatively soft, this has advantages in giving the floor paint a better key. Most good quality multi part floor coatings will flow into any small marks as they will in concrete which almost always have holes/gaps. A possible cause for the bubbles is using the spiked roller too quickly introducing as much air as taking out, something I had to work very hard on telling my operatives. Normally the coating is applied in at least 2 layers so any defects can be corrected. Watco are a good supplier of coatings and have a good technical side to assist(they are one of hundreds of suppliers and they are not cheap) I have used them on many projects over the years and the only problems I had with them was on structural products. 

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Thanks for the tips! 

 

Given that I had Friday off work, which was due to be my original XI kit collection date, I decided to give the garage a clean and prime the larger section of floor. I've been doing some tiling, and did all the cutting in side so the floor was filthy. I used way more primer than I had on the smaller section of floor, as I wanted every chance of a bubble free floor this time! This coat was applied neat, and is much more obvious. It took about 2.5 hrs to dry, with a decent flow of air through the garage and a pair of small heaters running to keep the temperature up.

 

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Once I'd persuaded the Mrs to lend a hand and to not do anything else with her Friday evening, we made a start on the compound. Whilst I'm happy to sling 25kgs bags of powder about and run the mixer at the same time, not everyone is strong enough to manage both. With me lending hand with the mixing, things progressed well. This way I could pour a full bucket on the floor and give it a decent trowel about whilst the next batch was being mixed. This area is about 25m2, much too big to do well solo I feel. I'd say it took about 2 hours to get it done. This did include some panicking as the metal dam sprung a leak at either end! I thought I'd fixed them both, and we got to the point of it all being level enough and up to the dam to give a nice sharp edge.

 

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It was at this point that I got called out with work, and had to leave the last bits of cleaning up to the Mrs whilst I went out. I presumed all was well, as the leaks had stopped.

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However, once I got back from work 4 hours later, all was less well than I had expected. 

 

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The leak that i had thought plugged clearly was not. Quite a bit of the compound had flowed out and into the hole for an old air brick leaving a shallow slope where it had been flat. This was quite disappointing, as it had looked so good before I went out! Over that end section the compound is now quite thin, and there's the obvious lack of a nice edge to it to deal with too.

 

Having done an initial look I can find a few products that can be put down to nothing, or a feather edge. I'm hoping these can be used to correct the lack of a nice even floor. I'll be ringing Instarmac on Monday to see what they have and what they suggest as the best way to go. I'd just get another bag of the HD Top but its meant to be layer at least 5mm thick which won't work all the way across. I'm hoping I can lay it thinner and take out most of the new slope!

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Why not do a cut back 100 to 150mm and scabble back the edge to depth, then you can apply topping to new edge. I would strongly advise against feather edging as very few materials can handle it over the long term, far neater and better to form a good square edge and if required make a feature of it introducing an expansion gap, later filled with suitable mastic which can be almost invisible.

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The section thats flowed away looks to be more like 500-600mm, but that could work. Is there a sensible way of cutting both the sloped bit back and making an edge without cutting into the dpm? As I've never used one before, can a floor grinding disc be used that accurately?

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Thinking about it, as I've poured it at more than the minimum of 5mm, I reckon I could get away with just cutting down the bit where the slope is less than 5mm, ie the bit furthest from the dam? There's a small step in the floor that was exposed when the compound flowed away, so that would give a logical edge to work to as well.

 

That way I wouldn't need to risk cutting into the DPM, and any join lines would be invisible under the paint anyway. Reckon that would work?

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If you use your grinder on a timber and measure to just cut into surface 5mm this is the best way to control the depth of cut, ideally with a diamond disc as the wear rate is slower so the depth will remain constant. Personally I do not see the risk in the dpm being cut as the coating you are putting on is waterproof and is  a dpm in it's own right. If you're doing any more shuttering, never underestimate the forces and flow ability of free flowing materials, always make proper restraining frames and seal any joints, clay is good and cheap.

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Following @Snags suggestion of cutting the floor back to a square edge, I got myself a diamond grinding cup this afternoon. Not having used one before I was a bit nervous of how it would cut, but I need not have worried as it was very controllable. I did have to take the guard off the grinder to use it, but thats no big bother. I then set to with a spirit level and marked out where a 5mm gap appeared by rolling a 5mm drill bit about under the level. Where it snagged, I drew a mark and carried on across the floor in 6" steps.

 

Having spoken Instarmac's tech team, they also said I could use the HD Top down to 3mm over the existing layer. This may not sound like much difference, at only 2mm less, but it means that I only had to cut back a relatively tiny amount of the existing layer due to the exposed step in the floor. So what I feared would be a massive ballache was only 45 mins work in the end! The cut back section was then given its first coat of primer in anticipation of laying the correcting layer tomorrow. 

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At this rate you will make a professional screeder, as with most things it is worth a little extra time and effort to properly prepare, the end results will be great. I laid my garage floor over 20 years ago, although had to tile the mid section for the wife( not buried under, which she can confirm😨) and it is still looking good.

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That's most kind of you to say! Whist I'm not the fastest worker in the world by a long way, I do like to think I can achieve a reasonable level of finish so its good to see that a pro thinks I'm doing ok!

 

In one way, having to do this extra step is making things even better. The end of the floor slopes away more than I realised, so the extra layer will actually make it flat and level! Equally, I'm not aiming for level as such, more that it ends up flat so that I can roll engine stands and the like about with ease and not end up kneeling on any little bumps or divots as that's a massive pet hate of mine. I think I've done a decent job of it so far, so it makes the cost of the materials easier to stomach.

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