The unforgiving nature of concrete and the dangers of Ram Board


As I’ve said before, I do love concrete. Though, recently, my love affair with concrete has been tested and I have started to see a side of concrete that I do not appreciate as much as much. This is, of course, it’s unforgiving nature.

I’d been told this before by a concrete contractor. He said, “I hate working with concrete. It makes me very nervous. You only get one chance with it.” It’s one thing to hear that but I’d never experienced this myself before. Until now.

OK, so let’s start at the beginning, just after we’d poured the concrete floors. We’d been told to be VERY CAREFUL with the floors after they had been poured. They take 28 days to cure, so anything done to them in that time and, following this prior to sealing, will effect the outcome. We had simply wanted a troweled and sealed concrete floor, without any fancy finishes. So that meant we had to protect them from the other trades coming in. We were recommended to use a product called Ram Board – a temporary floor protector.

So we ordered the product and proceed to lay it out across the whole of our main floor and basement concrete. Now, if you actually look at the link to the Ram Board, it says, “lays out easily.” So you would think (as I did) that you simply roll this stuff out, covering the floor, secure it together, secure the sides and you’re done, right? Wrong! This stuff was insane to try and secure to the floor and secure it to itself. We were initially told to try masking tape or painter’s tape. Fail. We then tried packing tape (as the Ram Board seems basically like thin cardboard). Nope. Duct tape? Nope, not at all. Finally, the only stuff that we could find that was sticky enough to hold the board together and secure it to the floors was Tuck Tape (please learn from my errors). Neither the contractor nor the supplier could provide us with any other suggestions.


I will say this, and perhaps if you have or are planning to pour a concrete interior floor in a residential house, you will have noticed this, but every time I talked to someone about anything related to an interior concrete floor, it was as if we were the only people in the entire world to ever do such a bizarre thing. Trying to get any information out of anyone, including contractors, suppliers, designers, et cetera, was like beating my head against the wall – I couldn’t find any information. Even online the information and resources were incredibly scarce. So I do hope that this will be helpful to someone in the future, because I wish I knew then what I know now.

Ok, so that’s what we did. We tuck taped it down (NOTE: don’t do as we did). And for awhile we said, thank goodness for Ram Board! It saved us from the leaky chimney, from the muddy boots that the contractors wore into the house, from the incredible mess from the drywall mudders, and from our own sloppy painting.

Then about four weeks after we’d laid the Ram Board out, I went to the concrete wholesaler to pick up our sealant and wax for finishing the floors. He asked how we’d protected the floors and we told him what how we covered them. “You know that Ram Board can leave cure lines, right?” He said. Umm, no and I don’t even know what that is (I’d never heard of ‘cure lines’ as a term before in my life – never in all of my exhaustive research on concrete). “Well, hopefully not,” he said. “How do you prevent cure lines,” I asked.

“I don’t know. I’ve never used Ram Board before.” He replied. (See what I’ve saying re: beating head against wall?)

Well, I couldn’t do anything about it now, and I still didn’t know what cure lines were, so if we got them then I guess we’d have to figure it out later. Another month passed.

Finally, we were ready to expose the floors and see what lay beneath. We started with the basement and to my horror, the board, no, the Tuck Tape, was really fricking hard to remove! As we started to pull the board away, the tape began to release, but…


Oh God, no. FML.

All around the perimeter of the floor was this. In spots, not so much. In others, a nightmare.

We got down on our hands and knees and started scraping it frantically with a razor blade and a hair dryer (seriously). The tape started to slowly release. Ok, good (kind of) we can fix this, I think. Although there were dozens of areas like that in the photo.

We decided we would get the rest of the board up and then proceed to take the tape off the floor. As we continued removing the board in the basement we worked towards the interior walls.


What?! NO!!!

Yes, this is red chalk. Deeply pigmented red chalk. Why would we have red chalk on our floors, you may ponder. Well, the framers, had chalked the floors to mark the walls for framing – a typical practice in a basement that will be covered with laminated, hardwood or carpet – but not on a finished concrete floor! Oh my god.

Well, I guess we have a red concrete basement floor now, I said.

But hey, no cure lines!

(I can joke about it now, but this really really sucked.)

Over the next two days, I spent on my hands and knees, scrapping the red fucking tape with a razor blade and hair dryer (I believe it was in the range of 20 hours of work). How we were going to get the red chalk off was another question. I figured (naively) that it was wipe off with soap and water, and so, I futilely attempted this.

Nothing. It did absolutely nothing.

Desperate, I got my palm sander out and sanded a small area in the closet with 80 grit sand paper. Hmm. It started to come up – ok, this is good. Although my measly 4″ palm sander would take a lifetime to try and get the roughly one 1/4 of our basement that had red chalk dust clean.

Bizarrely, on my day off, sweating and angry in the basement, perhaps by the grace of God (or whoever), a stranger showed up at our door. It was a Tuesday afternoon and we don’t get people just dropping in. We are in the middle of nowhere. It was a guy who we were actually supposed to have a tour of his house some months before, but we’d gotten busy and never gone. He was coming by to see how things were going and to check out our house (I think he was just snooping though really, as how would he have known someone would be around on a Tuesday afternoon). Naturally the discussion turned to the concrete floors, (which he also had!) and he asked how we we were going to finish the floors. Not sure, I told him. He informed me that he had in fact wanted to grind his floors to expose the aggregate, but when they came to do this, they found the floor too hard to work with. Because they had intended to grind the floors they did not cover it so it was covered with paint and drywall mud and all sorts of other crap. After much of their own stress, they decided to try to sand off that layer of crap. They rented an industrial floor sander, like the ones they use to refinish decks and old hardwood floors. It was a fair bit of work, he told me, but it removed all of that junk and left the natural grey floors. You should come check it out, he told me.

I had too much work to do. I needed to get the main floor board up and see what was underneath. I was relieved to find that, for whatever reason, this board and tape came up much better and there were only a couple spots with Tuck Tape residue left behind. Wow, must be my luck day, I thought. But then I stepped back and surveyed the great room. Sonuvabitch.


It may be faint in the photo, though it is much darker in person… you see those lines running to the end of the room? Yup, those are cure lines.

I was beside myself.

After being super depressed for the next few days, talking to contractors, suppliers, builders, and trying to think if there was anyway to fix this multitude of problems that we were now facing with the floors.

(By the way, I also researched “cure lines with ram board” in concrete floors. And wouldn’t you know that the only way to “fix” this was to prevent it from happening in the first place! By using a special vapour permeable floor tape! A tape that was not available through our supplier nonetheless… Rage.)

After talking to numerous people we narrowed our options down to four:

  1. Live with it. Gah, concrete is unforgiving. You mess it up and you have to live with the shame of it for the rest of your life. Probably though you will get over it and not notice it eventually. But as a recovering perfectionist, this was a stretch for me. A leap of faith that I wasn’t ready to accept without trying something – anything.
  2. Creative acid staining. The suggestion was to stain the area around the cure lines a darker colour then stain the whole floor in another colour. This may or may not work and to be honest, I don’t like the look of acid staining anyways.
  3. Grinding and polishing. I like this look, but it is very very expense ~$10/sq.ft. This is where the top 1/8″ of the concrete is ground off and polished to expose the aggregate. This was the only option to guarantee removal of the cure lines and chalk in the basement.
  4. Sanding. This is an option made only by the stranger that showed up at the house a few days prior. I found no information online about this except for one article that said you could sand the floor to prep it before staining to even out the finish. There was no guarantee that this would work, but it was probably the one with the least risks associated.

I called up the rental store and asked if I could rent a floor sander for the weekend. In talking with the stranger about the concrete floors, he told me he had used 60, 80 and 120 grit sand paper on his floors. Now I needed to go a bit deeper to see if I could get the cure lines slightly reduced, if not eliminated. I elected to start with 24 grit. Again, I will say this was a total experiment and I had no clue what I was about to get myself into.

I, of course, did not tell the rental store that I was going to use it on a concrete floor as this may raise some eyebrows. We decided to start in the basement because if we did fail, at least I would prefer to screw-up the basement over the main floor.

And so, on Friday we spent the evening like this:


It was a crazy crazy amount of dust – crystalline silica dust to be precise, which interestingly is super cancer causing. But ever so gradually as I went over and over the floors on the second and third passes with 24 grit sandpaper, the red chalk started to disappear. At the same time though, where the Tuck Tape had been stuck to the floor, it showed the residue of the adhesive more clearly. This too had soaked into the floor. The sander was not localized enough to get at this, so it had to be done on hands and knees with the palm sander (which did remove the adhesive residue) and some serious elbow grease.

We then made passes with 40 grit and 80 grit paper. I had been worried that the sanding might just “grey out” the floors into a bland pattern, but this wasn’t the case at all. Impressively, this actually exposed some interesting tone and variations in the concrete that were not there prior. And in some areas that were gone over a bit more heavily, some aggregate became exposed as well. The industrial sander worked well in that it covered a broad area with out leaving any sort of pattern to its movement. In that way though it was also really hard to control. Weighing about 100 lbs and vibrating across the floor in a seemingly random pattern did end up leaving some unsightly dings in the drywall that will need to be patched later.

After the dust settled the next day (literally), we surveyed the situation and were happy and relieved to see that the vast majority of the chalk had been removed, and with the hand sanding, the tape lines too.

With some returning sense of optimism, I decided to try it on the main floor. I followed the same process going over with the 24 grit sand paper 2-3 times, then the 40 grit and lastly the 80 grit paper, vacuuming with the big shop vac between each pass in each room. It was tough to tell at first, but the lines seemed to be less noticeable. But maybe it was just the dusty residue. We decided to leave it again for another day.

On the third day we returned with the plan to clean the floors and seal them if they did not look like a total disaster. We vacuumed the entire house another two times.

IMG_3127Well, I’ll be damned, they looked better. They weren’t perfect, but definitely a bit better. I could still make out the cure lines in places, but they were less continuous overall.

In the photo to the left, you can slightly see the cure line running in the right top corner on the diagonal.

So, relatively satisfied with the outcome, and happy that we had at least done our best to fix it, we decided to seal the floors. I had picked up a 20% solvent acrylic sealer (totally poisonous stuff). They recommended using a nap roller to apply the sealant, but we had used that method for the concrete basement walls and it sucked, so instead we decided to use the ol’ “spray and back roll method.”

This is just what it sounds like, spray the stuff and use the roller (pulling backwards) to smooth it out. Try not to overlap the rolls too much and just apply the spray lightly in a mist to cover the area. I sprayed and the wife rolled. This method went about three times faster than just the roller method and it gave a nice even finish. It took about 45 minutes to cover 1200 sq.ft.

We then proceeded to the main floor. This solvent sealer is very sticky as it starts to try. We’d taken a short break to breath non-toxic air before returning to the main floor. It started well, but about 1/2 way through the sprayer became gummed up with the drying sealant and I could not turn it off! It was spraying uncontrollably, including onto the freshly painted wall! Yup, nothing is easy when building and nothing really goes as planned.

The rest of the main floor ended up taking four times as long as the basement as I was constantly stopping to clean the sprayer. In hindsight, I would recommend having one sprayer for every 1000 sq.ft.

Finally though we finished. It was sealed and now there was no going back at all. Fine by me. I was so done with these floors.

We left all of the windows open for the next 24 hours to let the house air out as the sealant smelled very potent.  When I stuck my head in the window the next day though I was very pleased to see that, well, the floors looked pretty awesome:


Again, there were spots that were not perfect and in the second bedroom there was still a very dark line that I was not at all able to reduce. Can anyone say: throw rug? But nonetheless, I’m relatively happy with them. We tried and didn’t totally fail. Although I wish I would have known how to prevent the cure lines in the first place (now I do and so do you): Special tape!

Main Floor Concrete

We were very happy with how the basement concrete slab turned out. Tyco Concrete had come through for us on short notice and they had done a really nice job. So one week later we had them come back in to do a second pour, this time for the main floor. We had really debated about how we would like to finish the main floor concrete though despite months of reading and looking.

I should digress for a moment and simply state our reasons behind the concrete floor in the first place:

  1. Thermal mass – thermal mass is a the ability of a material to absorb and store energy (heat in particular). For passive solar heating in the winter months, the sun shining on the concrete will act like a battery, gaining heat during the day, and allowing it to release the heat in the evening. You could use a tile or brick to similar effect. A large brick or stone wall would also work, but you need the sun shining on it. Conversely, in the summer and “shoulder” (April and October) months you really don’t want the sun shining on the thermal mass as this can lead to overheating (thus the importance of passive shading and overhangs).
  2. In-floor heating – we still need a heat system. It is true that our thermal mass is not quite as good as if it had no in-floor heat (a colder mass will heat MORE than a mass that is already pre-heated) – however who wants to walk around on a cold concrete floor in the morning, honestly?
  3. Concrete is sexy.

Okay so now that that is cleared up, we had to decide on how we would like to eventually finish the floors. We had already decided that acid staining and dyeing the concrete was really not our thing – much too fancy-pants for us. That basically left us with two options: power trowel (same as the basement) or grind and polish. Both looks we really like.

Grind and polished concrete – not our place

The grind and polish look is something I really like. You need a concrete grinder machine with diamond discs starting with very rough grits of 80 and 120, which grind the top layer of concrete off exposing the pea gravel aggregate that sinks to the bottom and progressing up to finer and finer grits. Eventually getting up to 800, 1200, 2000 grit discs that give a highly polished look to the floor. You get a lot of interesting variation and different colors of the pea gravel coming through (although some people specify all grey or black pea rock if they want something more consistent). There is a couple downsides with this for us though. Firstly the concrete topper they were going to pour was only going to be 1.5″ thick, which is pretty darn thin. Although you are only taking about 1/8″ or so off the top, we had 1/2″ PEX in-floor piping and metal concrete mesh overtop – grinding too much off could be a horrible thing. We had seen this first hand – a good friend had built an eco-house in town and wanted a ground and polished concrete floor. Unfortunately the contractor ground off about 1/4″ too much. It looked great initially, but the layer of concrete over the in-floor heat was so thin that in the next few weeks the concrete started to crack badly following the pattern of the in-floor lines… It looked so bad. On a thicker floor you’d have nothing to worry about, mind you. But needless to say I was a bit paranoid of that risk. The second consideration is that you need to grind and polish before drywall as it makes a crazy mess. And you can’t grind and polish until it has cured for one month. That would mean that we would have to put the interior on hold for a month which we really did not want to do.

The other option was to simply power trowel the main floor, same as the basement. We have seen this look a lot in some more modern homes and I really like the simplicity of it. It is not complicated at all and is in fact the simplest, cheapest and easiest way to go (pour and trowel is about $2.50/sq.ft completed while the the grinding and polishing cost would be an additional $5-6/sq.ft above and beyond). You pour floor, power trowel the crap out of it and call it a day (in 28 days you can seal it, buff it, wax it, whatever). As I said we liked how the basement floor turned out, particular the very “swirly” areas, as my wife calls them. I hoped that we could make the floors slightly different then the basement floor still though. I looked into the possibility of adding a bit of black pigment to darken the grey slightly – however I abandoned this idea after I was told the pigment dries the concrete faster and can lead to an uneven finish.

Eventually the decision came down to, what is the simplest option? Through this process we have found ourselves periodically down a rabbit hole wondering how we got here and how everything became so complicated. Our answer in those situations, or when we’ve debated about two or three different things is – simple is always better. The more complicated, the more things can go wrong.

So I told the concrete guy, “finish the concrete just like the basement – only, more swirly please.” (He told us that the metal blades of the power troweled as what make it swirled and darker, but troweling longer and on a higher speed for the blades, they can darken the concrete more).

The morning of the pour was crazy again, our builder did not realize they were coming so early with the concrete truck and he’d left a bunch of stuff around the house. I received a text at 6:30am from the concrete guy – “someone has to get over here and move all this shit – truck is here.”

IMG_2982Fortunately we are living very close right now so I threw on some clothes and was out the door. We frantically (concrete starts to cure as soon as it leaves the plant – being 30 minutes from the city, every extra moment counts) moved a trailer, two big garbage bins, scrap wood, plywood and all sorts of junk. Meanwhile the rest of the concrete crew was even more frantically throwing down the concrete mesh (which provides structural support, like rebar, in thinly poured floors like ours). This stuff was crazy heavy and looked so cumbersome to work with, but these guys were pros, they had the whole floor laid and secured in about 20 minutes.

And so the pour began again. I could not stay and watch and truthfully, I did not want to see it. Seeing that grey/brown sludge of mud being rolled in and dumped on the floor simply made me nervous. I just wanted to see it pretty at the end.


When we got home all was quiet again. We went to the back door and peaked our heads in.


So swirly!


So very swirly!