Now for me, I suppose one of the biggest reasons that I never took a good serious look a concrete roof was that I really never saw one on a home. That is unless I saw some news footage about an earthquake in some far off third world country, and then what I saw wasn’t pretty. Brick and cement homes with concrete roofs tumbled in on one another, like so many dominoes.
So I suppose I was like most folks in the US, Canada or the UK, in that I just felt a lot more comfortable with a lighter wood framed roof up over my head. Just to play it safe. However, then something happened that completely changed my view of the concrete roof and that was that I visited Mexico, and finally got a good close up look at a properly built, steel reinforced concrete roof.
Every building here has a concrete roof on it.
Now before I get into how they’re built and the benefits that they offer, I want to point out a couple of things. First of all you have to understand that building codes in most all third world countries are incredibly lax and pretty much non existent on the outer perimeters of cities, and populated areas. Also steel rebar is expensive to buy. Particularly in many of these poorer areas.
What I’m getting at, is the tumbled down building with a concrete roof that you have seen so many times on TV news, is the result of lack of proper steel reinforcing. Also a light sack mix of the actual concrete that’s poured is all too often a contributing factor to structural failure as well.
Then the last thing I want you to consider regarding the structural integrity of a concrete roof, is that bomb shelters are made out of cement. Stop and think about it for a second, or two. If you wanted to build an underground bunker to survive a nuclear blast in, what would you build it out of? That’s right! You would build it out of steel reinforced concrete and you better believe that it would have a concrete roof on it for sure. Concrete when “properly reinforced” is the strongest building material you can use.
Mexican "cementeros" do amazing things with concrete.
Mexican “cementeros” (cement workers) do amazing things with concrete and all you have to do is lay your eyes on one of their precision formed in, full concrete winding staircases to make a believer out of you. You see, for one thing labor costs run substantially lower down there and as a result so many of the things that they do and build with it would be prohibitively expensive up in the US, Canada, or the UK.
At the same time, you have men in countries all over Latin America that started in working with their father or uncle on their first concrete roof when they were just kids. It’s all they know and they know it well, so a cementero in, say his mid 30s can quite commonly have some 25 or more years of forming, and pouring concrete notched on his belt.
Now a concrete roof doesn’t rot, can last pretty much forever, only requires a coat of good paint to seal it up, is completely termite proof, flame proof, and is strong enough to support a basket ball court with a full team playing on it. Also because you don’t have the toxic substances in them that you find in so many standard conventional roofs, the water that flows off of a concrete roof is pure as the driven snow.
Still on more thing that I was struck by when I would stop to watch a group of Mexican cementeros forming and and pouring a proper steel reinforced concrete roof, was how far they could span. Even with only a 3.5 inch thickness, spanning up to 18 feet seemed to be no problem, and that’s with zero underpinning support.
Still another aspect that I was struck by, was their amazing ability to incorporate decorative features like corbels and formed cement rafter tails into their work. Also building a pitched concrete roof, complete with hips and valleys was also done, although by and large, the standard flat roof seemed to be pretty much the norm.
Installing the initial rough underpinning for a pitched concrete roof form on a cement block building.
The way they form in a concrete roof in Mexico, is really quite basic. They start by decking the ceiling in then they use posts and improvised lateral underpinning to hold the deck up, and keep it from sagging. That’s it. Then of course they lay in the the rebar grid-work, electrical conduit, and plumbing then pour and finish it. It’s basically a cement slab built on top of the walls.
Now they do use a heck of a lot of posts as you can well imagine because they have to hold up literally tons of wet cement, and it all has to be perfectly flat when the concrete roof cures. So would you believe that they use tree limbs for posts? They’re cheap, and strong. They simply stick them in place, shim them up to level then nail, or screw them at the top end. That’s it.
Now the concrete roof has been around in developed countries like the US, Canada and the UK all along but costly code stipulations meant that with very few exceptions, this type of roof was only found on commercial buildings. You see, due to weight considerations, cement walls or heavy steel framework, and underpinning is the standard requirement. Even so, there have been some new developments.
These developments come in the form of lighter concrete roof systems with new technologies like fiberglass joists and even new harder types of cement. Also there are now several types of engineered, factory made systems to choose from that incorporate pre-cast panels that set into, or onto special joists. Now the nice thing about these engineered systems, is that they’re capable of surprisingly long spans.
Pre-cast concrete roof panels.
Now perhaps the simplest of these pre-cast concrete roof systems is basic 4 X 8 foot sheets that are cut with a hand held circular saw with a diamond blade on it. Now due to the fact that these sheets are thin, you don’t get the structural support that you would with other heavier systems though. Rather, these cement sheets are meant for covering and offering long term protection on existing roofs like steel roofs.
So then what does the future hold for the concrete roof? For the answer to that question all one has to do is look to increased Canadian and US logging restrictions, leading to steady climbing lumber costs. Then add in rising crude oil prices, to see that this material is only becoming more cost competitive. It is, after all by far the superior building material from virtually all points of view..