diy firepit/patio area with cement
April 1, 2019 9:23 AM
I am making my own fire pit area in my back yard, and I was planning on using something like THIS to make it look properly bricked in. My partner thinks that small cement bricks will crack and break down more quickly, and therefore thinks that this plan is flawed.
His belief:
- the smaller bricks will crack and break quickly, or at least more quickly than a larger slab
- that somehow the water will get into the smaller bricks, freeze, and then crack them, and that this will be more of a thing than with a large slab
- He thinks we should pour cement in the whole area and then use my brick-shape thing to make indentations so that it LOOKS like it is individual bricks, but it is actually a slab.
My belief:
- the smaller bricks would last longer
- the water freezing in them would be no more with small bricks as large slab
- that the large slab is more likely to get heaved about with frost and ground movement etc, and that adjustments would be about a billion times harder with a slab than with the small bricks.
Who is right?
His belief:
- the smaller bricks will crack and break quickly, or at least more quickly than a larger slab
- that somehow the water will get into the smaller bricks, freeze, and then crack them, and that this will be more of a thing than with a large slab
- He thinks we should pour cement in the whole area and then use my brick-shape thing to make indentations so that it LOOKS like it is individual bricks, but it is actually a slab.
My belief:
- the smaller bricks would last longer
- the water freezing in them would be no more with small bricks as large slab
- that the large slab is more likely to get heaved about with frost and ground movement etc, and that adjustments would be about a billion times harder with a slab than with the small bricks.
Who is right?
They make concrete stamps that give you that same pattern without separating the material into individual "bricks".
posted by humboldt32 at 9:46 AM on April 1, 2019
posted by humboldt32 at 9:46 AM on April 1, 2019
Both options are made with cement and both should last the same, if properly built. The freeze thaw cycle of damage will be the same for both. However, you are right slabs are much less forgiving of mistakes, which are common*, and 'adjusting' generally just means replacing the whole section (and it should be made in sections) like SaltySalticid alludes to.
But, I'll warn you though - those small concrete patterns are impossible to work with and I've yet to see a successful project that used them - a much better bet is just buying pre-made concrete pavers in a pleasing design. Yes, they cost more, but so does your time, and how many of those forms are you going to get? And how much cement are you willing to experiment with?
I've poured some concrete and I'm generally willing to diy and encourage others towards the same but if you plan on more than a couple of square feet I would strongly reconsider building your own pavers. The big pro for a slab is that they are easy to maintain once in place. Yes, lots of prep work, but I would put a slab down and spend theat decorative money on the pit or chairs or lighting or such. And the big pro for commercial pavers are consistent, look nice, and much easier to work with, and you get that look you want. There is no pro for the home made.
*for example one common mistake is to leave the aggregate (usually rock) exposed in the surface of your pour. These rock bits are a very handy conduit for water to get into the work and then the freeze and thaw and repeat and either the concrete breaks or the rock pops out and either way the surface quickly degrades. That's why finishing like screeding and vibrating are so important.
posted by zenon at 10:15 AM on April 1, 2019
But, I'll warn you though - those small concrete patterns are impossible to work with and I've yet to see a successful project that used them - a much better bet is just buying pre-made concrete pavers in a pleasing design. Yes, they cost more, but so does your time, and how many of those forms are you going to get? And how much cement are you willing to experiment with?
I've poured some concrete and I'm generally willing to diy and encourage others towards the same but if you plan on more than a couple of square feet I would strongly reconsider building your own pavers. The big pro for a slab is that they are easy to maintain once in place. Yes, lots of prep work, but I would put a slab down and spend theat decorative money on the pit or chairs or lighting or such. And the big pro for commercial pavers are consistent, look nice, and much easier to work with, and you get that look you want. There is no pro for the home made.
*for example one common mistake is to leave the aggregate (usually rock) exposed in the surface of your pour. These rock bits are a very handy conduit for water to get into the work and then the freeze and thaw and repeat and either the concrete breaks or the rock pops out and either way the surface quickly degrades. That's why finishing like screeding and vibrating are so important.
posted by zenon at 10:15 AM on April 1, 2019
Have you priced out using precast concrete pavers vs pouring your own? Concrete is a fiddly in terms of getting the right moisture content, set-up time, curing time, etc. You'll have to buy special tools to pour a concrete slab following your husband's idea, or you'll have to spend so many hours spread out over so many days molding, waiting for setup, unmolding, and curing enough homemade pavers that are far more likely to crack or crumble than factory-made pavers. Like, do you really want to be spending 20 minutes a day for three weeks making 2 paver blocks at a time, just to save a hundred bucks over the cost of buying factory-made pavers? This is a situation where you can spend twice as much money and half as much time and have a nice-looking end result that will last for years, or half as much money and twice as much time and have something that's likely to fail. Regardless of what solution you go with, you need to invest the time and money to put in a proper base so it can stand up to frost heave.
posted by drlith at 10:39 AM on April 1, 2019
posted by drlith at 10:39 AM on April 1, 2019
If the size didn’t matter, we’d pour sidewalks to run for a whole block. But we don’t, we put in expansion joints. Expansion joints prevent cracking, control joints control and manage cracks. Using joints is critical, and pouring large slabs without them is Doing It Wrong™.
It is important to know the way the pros avoid at least some types of cracks. They use control joints.
posted by SaltySalticid at 11:02 AM on April 1, 2019
It is important to know the way the pros avoid at least some types of cracks. They use control joints.
posted by SaltySalticid at 11:02 AM on April 1, 2019
SaltySalticid is correct.
In my firsthand experience, both normal concrete and concrete pavers will crack and crumble fairly quickly in this application. Pretty sure you will want to use clay or firebrick to have much hope of this lasting more than a couple seasons.
posted by aspersioncast at 12:26 PM on April 1, 2019
In my firsthand experience, both normal concrete and concrete pavers will crack and crumble fairly quickly in this application. Pretty sure you will want to use clay or firebrick to have much hope of this lasting more than a couple seasons.
posted by aspersioncast at 12:26 PM on April 1, 2019
I'm planning a firepit/patio area, and coincidentally, my sister just sent me links to hobby sites featuring DIY concrete pavers for firepit areas. I let her know I'm not interested at all.
I don't care for the look of slab-cast concrete patios, which scream 'cheap' to me. Plus, I live in a northern climate and have seen what the seasonal stressors eventually do to all large areas of cast concrete. And when you eventually have to replace it, breaking up and getting rid of that large concrete slab is a lot of work.
I've built patios using wood, rubber, and precast concrete pavers. Preparing the site, regardless of what you end up using, is the most work; it has to be level and compacted so that the pavers will lay smoothly and evenly (preferably with a slight slope to enable water runoff) and won't sink or settle over time. If you're building the firepit ring using concrete or landscape blocks, the weight of that firepit ring requires either a leveled and compacted gravel base, or a cement slab, to carry the weight and keep the ring from settling unevenly.
For light-duty patios such as what you'll have surrounding the firepit, you can save yourself a lot of effort by using a manufactured panel paver base product instead of gravel. Basically, dig out, smooth and level the surface of the ground, lay these interlocking paver base panels, then set your pavers on top of them, finishing by sweeping in sand to fill the joints between the pavers. This sort of paver base is expensive but saves you a lot of backbreaking work spreading and compacting gravel. My sister and I laid our third patio using these panels and we were awestruck and thankful at how much easier the job was using these.
As practically everyone else has recommended, I'd go with individual pavers, because they're easier to lay, easy to replace if one is damaged, and look a whole lot better than a large slab of concrete. The smaller the pavers, the more work setting them, so I'd recommend a 12- or 16-inch square paver, which is about optimum in terms of ease of handling.
This can't be overstressed: preparing the site will be by far the most work, so don't be discouraged.
posted by Lunaloon at 6:06 AM on April 2, 2019
I don't care for the look of slab-cast concrete patios, which scream 'cheap' to me. Plus, I live in a northern climate and have seen what the seasonal stressors eventually do to all large areas of cast concrete. And when you eventually have to replace it, breaking up and getting rid of that large concrete slab is a lot of work.
I've built patios using wood, rubber, and precast concrete pavers. Preparing the site, regardless of what you end up using, is the most work; it has to be level and compacted so that the pavers will lay smoothly and evenly (preferably with a slight slope to enable water runoff) and won't sink or settle over time. If you're building the firepit ring using concrete or landscape blocks, the weight of that firepit ring requires either a leveled and compacted gravel base, or a cement slab, to carry the weight and keep the ring from settling unevenly.
For light-duty patios such as what you'll have surrounding the firepit, you can save yourself a lot of effort by using a manufactured panel paver base product instead of gravel. Basically, dig out, smooth and level the surface of the ground, lay these interlocking paver base panels, then set your pavers on top of them, finishing by sweeping in sand to fill the joints between the pavers. This sort of paver base is expensive but saves you a lot of backbreaking work spreading and compacting gravel. My sister and I laid our third patio using these panels and we were awestruck and thankful at how much easier the job was using these.
As practically everyone else has recommended, I'd go with individual pavers, because they're easier to lay, easy to replace if one is damaged, and look a whole lot better than a large slab of concrete. The smaller the pavers, the more work setting them, so I'd recommend a 12- or 16-inch square paver, which is about optimum in terms of ease of handling.
This can't be overstressed: preparing the site will be by far the most work, so don't be discouraged.
posted by Lunaloon at 6:06 AM on April 2, 2019
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None of your suggestions use brick. Brick are fired clay, and fire brick are the brick designed to hold up well to the thermal stresses of fire pits and fire places.
Neither of your ideas are particularly likely to hold up that well over time* when exposed to regular fire and also freeze cycles (*e.g. longer than 6-10 years). Of your two ideas, his is worse, because there will be no expansion joints and it will almost certainly crack within a year or so. Water penetration through the cracks is generally worse than water penetration through a finished surface.
A fire pit made with fire brick will last at least 50 years, and isn't really all that difficult, the idea is to grade the area, put down a base of crushed lime, then fit the brick in as tightly as possible in a pattern that you find pleasing.
But if you're set on the concrete forms, your way is better, that's why the product is designed to be used as it is. You can get a better finished surface by tapping/vibrating the mold for a bit while it's still wet, this will utilize the brazil nut effect in a way that will make the top part smoother and more impervious. I'd also recommend using a concrete float for additional similar benefits.
posted by SaltySalticid at 9:41 AM on April 1, 2019