What is the greenest way to build a deck? Is it okay to use pressure-treated lumber? What is the best way to attach it to the house? What kind of decking is the most sustainable, and what is the best method for attaching the deck boards to the framing? Should the surfaces be finished? With what product? These are just some of the questions I hear about creating outdoor living space.
My answer is always that the greenest deck is a patio. Sure, wooden decks or balconies are usually the only options if they have to be significantly above ground level, although there are masonry- and petroleum-based products that can work in those applications.
Outdoor living space is a great way to expand our living area without increasing the amount of conditioned space: it gets us out into the open air, into the nature we’re trying to preserve with the green building movement. But asking any “green” material to stand up to the environmental exposure a deck is subjected to is asking a lot. When the outdoor living space is going to be at or near grade, a patio—the masonry equivalent to a deck—can be a greener choice.
If the word “patio” conjures images of dirty concrete with weeds growing up through cracks, there are other options. Harvesting “urbanite” for reuse by breaking up the old concrete into manageable pieces is one example; overlaying a drainage layer and topping it with permeable surface paving is another. On a recent project, we used granite stones salvaged from a crumbling foundation, which our skilled mason assembled into the intricate, recessed patio shown in the photo above.
Commercially available, cement-based, interlocking modular paving blocks can be an affordable choice, although I am partial to square concrete pavers set in a bed of crushed stone for a more formal look, or flagstones (flat, natural “cleft” surface fieldstone) for a rustic feeling. An artist I know built a very interesting patio using a mix of broken stone countertops, tiles, and glass. Slate roofing could be recycled into patio paving, but, like tile, the small, thin pieces would not be stable underfoot unless set into a bed of mortar. Stacked closely together on edge, though, the thin edges would create a unique, usable surface.
Brick, a classic patio surface, is hard to beat for its combination of warm color and texture. Bricks can be locally produced in most parts of the country or recycled from old buildings. Durability can be an issue in areas that freeze, though; look for “hard” bricks, tempered for use as paving, or be prepared for them to disintegrate over time into their original form of clay particles.
Drainage options will vary depending on several factors. If the patio sits on a well-draining site, it will be best and easiest to use a permeable base layer such as crushed stone and leave gaps in the paving material to allow stormwater to drain through. The gaps can be filled with the same material, or planted with moss (if it’s shady) or thyme (if it’s sunny). Weeds can be easily killed with a 50% solution of vinegar, or scraped out with a brush designed for the purpose. Personally, I would not use a chemical such as Round-Up or burn the weeds with a flame, but those are other options, probably no more harmful than standard deck maintenance techniques. If the site does not drain well, start with a well-compacted base of gravel with graduated particle size so that the particles lock together. On top of that, build a drainage layer using crushed stone, with a drain tile (4-in. perforated pipe works well) to direct water to another part of the site if necessary.
Keep the size to roomlike dimensions, and when in doubt, make the length 1.6 times the width for a pleasing proportion. Patios need a sense of enclosure to feel inviting; masonry walls or shrubs and plantings create a feeling of containment. When a tall wall looms over an abutting patio, bring the scale down with a trellis or pergola, or pull the patio away from the house a bit and plant a tall shrub or small tree between it and the house. Full sun can make a patio (or deck) uncomfortably hot; a patio umbrella or a trellis covered with vines provides respite.
Consider low-level lighting and a source for cooking fuel—wood or gas—in the planning stages. Outdoor cooking appliances keep heat out of the house (look for Energy Star models) and can be connected to natural gas or large propane tanks, if available on site. Or, build a fire pit or an outdoor barbecue. The kitchen has taken over the indoors as the heart of the home, the primary gathering spot; duplicating kitchen functions outdoors will ensure that the patio is well-used.
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Save the slate for roofing
As an ex-roofer, it's painful to read your suggestion: "Slate roofing could be recycled into patio paving ... Stacked closely together on edge, ... the thin edges would create a unique, usable surface."
Your suggestion to take tens of thousands of dollars of slate roofing to make a small patio (presumably for a wealthy client interested in a patio with a "unique" look) is disturbing. Fortunately, the suggestion is unlikely to be taken, since the edges of roofing slates are fairly sharp. Such a "unique" patio would definitely not be barefoot-friendly.
Here's my suggestion: if you are lucky enough to have salvaged tens of thousands of dollars of roofing slate, put an ad on eBay so it can be purchased by a roofer.
Martin, the next project on the house with the granite patio is to remove the worn-out 150yo slates from the one section of the house that still has them. Ice dams and botched repairs have used them up. We are taking steps to reduce the ice damming, but the damage has been done. A slate roofer looked at them and said that at the most, 30% of them could be recycled but that it would be difficult to match the color perfectly. Maybe I'll use them on a shed, but they certainly aren't worth tens of thousands of dollars. I've bought used slate roofing for a dollar each at junk stores. The sharp edges would not be the best for bare feet, but placed close together and infilled with stone dust they would be no worse than crushed stone and much more interesting. Or they could be wet-sawn in half to get a less sharp surface.
I'm not saying that used slate roofing is always my first choice for patios--but thinking outside the box, patio paving is one possible use for them. Selling on Ebay is another, if you don't want to reuse them on the same site where they've been for a century.
I just measured my used slates
I just went out to measure my used slates, which are stored on edge. They're 1/4 in thick and 16 in. long. Forty-eight slates take up exactly 12 inches of thickness. So if you can buy used slates for $1 each, your patio materials will cost $36 / square foot. Ouch!
For a 15 ft. by 30 ft. patio — admittedly a large one — the materials cost is $16,200. I'll admit, that's not "tens of thousands of dollars" — but it's out of my price range.
What, can't afford to build green?
I got the idea from a photo in a book that showed something similar as edging along a path. Maybe that's a better use for them than trying to fill a 450SF patio. Or you could combine them with recycled cobblestones, Belgian blocks or bricks to create a pattern. Or cut them into 2" strips and space them 1" apart, and fill with stone dust or Polysand to cut your cost estimate by 75%. Or sell them on Ebay and buy manufactured concrete pavers, it's up to you--
One more thing
I was thinking more about cost for patio paving materials. The granite stones shown above came out of the basement of the same house, so we could dig down, install an interior drainage system and radon barrier, put proper footings under new structural columns, and pour a new slab. The old stones were so beautiful that everyone agreed they had to be used on the site. To go out and buy "antique" stones with such a patina would be very expensive--probably at least as much as Martin's estimate for using roofing slate as pavers.
The key is that the stones, like the slate, did not cost anything except the labor involved in moving them. They aren't worth a penny if you don't sell them. No cement had to be manufactured to cast them. No trees were cut to build a deck instead. New stone did not have to be quarried. Petroleum was not used to make pervious grids. Nope, just some rocks from the basement, and conceivably some rocks from the roof, with a great story and minimal energy behind them.
down with decks!
I'm with you, Michael - we're trying to avoid decks whenever possible. I think they're like jacuzzis, frequently desire, rarely used.
Lots of food for thought here, Michael, like most of your blog pieces. Thanks.
It's a good idea. Patio give
It's a good idea. Patio give occupants a surefooted feeling, and allow them to connect with nature. Even in high-density communities, it is worth to construct some public patios to facilitate outdoors activities.
However, Do you think that an on-roof patio above apartment building would be more or less the same useful as an on-ground one?
Sorry Tong, I missed this comment the first time around. Some of my favorite outdoor spaces have been on the top of tall buildings. You get a vantage point to take in the views, and a sense of privacy if other, taller buidlings are not too close. String up some christmas lights and turn on the music and you have a party.
I've seen rooftop spaces built using decking material on top of the gravel ballast on a built-up roof, and I've seen concrete pavers on top of gadgets made for the purpose. I've built many decks over rubber membranes, protecting living space below. These are all in a category of their own--not tacked on like most decks, but more of a true indoor/outdoor transition space.
Let's hear it for decks!
I love a good patio as much as the next guy, but it's a long way down from our 2nd floor main living area. We use our deck all the time, and have used locally-milled cedar for all posts and railings. We've also found some great water-borne natural oil wood finish that is low-VOC and cleans up with soap & water to finish it. So don't dis the deck!
What's the finish?
Lorne, what is the finish you've found? How does it hold up? What's your climate? Although I prefer patios whenever possible, we still design and build plenty of decks. We don't use composites as a rule, so we're always looking for a good sealer.
As a 'complete' residential and commercial designer, I have used old reclaimed bricks of all varieties, including a lot of non fired old chimney bricks as patio, walkway, entrance and driveway material by simply using a long and shallow tray to soak the bricks (very dry) in a Concrete Sealer - completely immersed- for a period of an hour or so and then letting them dry. Then it is simply a matter of what type of strata you want to place them on: it could be simply well a well drained soil (which allows for vegetative growth between on simple foot traffic areas or a sand base which allows for minimal growth between bricks. I prefer a well prepared based that allows for drainage with an infill between bricks of a rich topsoil to permit the planting of various herbs and mosses that allow for a same season and constantly thereafter 'been here for generations' look. There may be a loss to freeze/thaw but I have found that if you get the solution just right - there aren't any 'failures' and the look is what every 'old country house' can really celebrate.
We are about to install a patio outside our backdoor. So the patio butts up against the foundation. Our carpenter wants to run metal flashing down between the foundation wall and the edge of the patio. The way we see it, water would then run down between that crack (this is not a well-covered entry) and not really have anywhere to go. Does anyone have any insight into this detail?
Photo below: the block will be replaced by patio.
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