Deck to Hot? A Pergola May be the Solution


It’s the first thing that catches your eye in a yard, rafters with slats crossing across them. A pergola defines your yard, being the eye-catching structure covering your deck or patio.

The point of a pergola is aesthetics and shade. Increasing the beauty of your deck while making your deck more comfortable. Decks are awesome in the summer, but they can become unbearably hot. A pergola provides shade taking the burn off the summer sun while still allowing you to enjoy the summer.

While shade and aesthetics are the main reason for a deck pergola, there are many others. Ways that a pergola can improve your yard and deck. Here are a few additional uses of a deck pergola.

Increase Privacy

There is something about the feeling of a roof above our heads. We just feel more comfortable. Maybe chicken little got us all, “The sky’s falling.” Hoping the rafter will save us. But seriously, something is comforting about having a shelter over our head. A pergola provides this sense of cover while still allowing the warmth of the sun and cool breeze.

Curtains or privacy walls combine nicely with Pergola’s walls. Increasing the sense of privacy while sitting on your deck. Closing in your deck from the world around it.

Defining Space

A shed without solid walls and roof. Or more preciously open walls and roof. Defining the deck all while still be outside. The same way pergola increase privacy, they define the area. Often built with four-post, creating corners to define your deck. Contrasting sun and shade-giving you atmospheric reminders of defined space. 

Celebrating Outdoor Parties

Pergola’s are great for decorating. Decoration can be hung from the rafter or post. Just think of the last outdoor wedding you were at, I bet there was a decorated arbour or pergola. They are just a festive structure. From Christmas balls and wreaths or bows and curtains. They all go well decorating a pergola to celebrate.

Hanging Garden

Back by the Mediterranean Sea where Pergola first got their start and still are popular. The rafter covered with vines providing both shade and beauty. Pergola are perfect for hanging plants off, either vining up the post and rafters or pots hanging down. Want to bring nature and your garden to your deck? A pergola allows you to surround yourself with plants, all while enjoying your deck.

Increase Yard Aesthetics

As I first mention, pergolas are an eye attracting structure. Walk into any backyard. The first thing you will look at is the pergola. Dressing up a plain deck or patioOpens in a new tab.. There is something about the slats and holes that intrigue us, that draw us in. Aesthetics’ can be further enhancing with decorative cuts on the ends of rafters and beams. Purlin patterns also help to increase beauty. Decorative knee braces are a wonderful touch, taking the post and whole pergola to the next level. All while making the pergola sturdier.

Shade

Last but the biggest reason for a pergola is the shade they provide. Shading your deck from the searing heat of the sun. Like sunglass for your deck, dimming the sun’s intensity. A deck with high sun exposure will become uncomfortably hot. Shade from a pergola allows you to enjoy your deck again without being cooked alive. Shade reducing your decks’ temperature by a few degrees, making all the difference in the summer heat. Think of it as A.C. for your deck.

Unlike a roof, pergolas don’t block the sun but provide relief from its intensity with the rafters and purlins partially shielding your deck from the sun. The amount of shade is determined by the number of purlins, rafter and their slope and angle to the sun. Raising some great questions about pergola design.

How far apart should pergola rafters be spaced?

The larger framing members of the pergola are not for shade. Therefore, they are commonly placed at 16” or 24” o.c. Common spacing for framing roof rafters. For aesthetic reasons, they need to be consistent. Similar to deck railing, adjust on centre spacing for consistent spacing along the beam.

For example, if you have a beam 11’ (132”) and you want 16” on centre spacing.

132” divided by 16” equals 8.25. Round up to 9 and divide again.

132” divided by 9 equals 14.66” or 14 21/32” (8’ high we can fug this number a little to 14 5/8”

Adding one rafter to start and we need ten rafters at 14 5/8” on centre.

How far apart should pergola purlins be?

Now, this is the real shade question. The smaller the spacing, the more shade they will create. More shade, meaning cooler deckOpens in a new tab. but to close together, and it just becomes a roof. I have heard anything from 24” to 4” on centre spacing. 24” spacing for purlins is just for looks and does little for shade. Think of this as a percentage game. How much of the sun do you want to block out?

A Purlin percentage example. 1 ½” purlin slats spaced at 16” on centre will block roughly 9% of the sun’s heat. The same purlins at 10” on centre will block roughly 15% of the sun. Of course, this is not an exact temperature gauge, but it gives you an idea. Decrease purlin spacing, increase deck shade. Purlins at 12” on centre are roughly 12%, which I think takes the edge off the sun without blocking the sun. But this is very deck specific depending on many other factors.

What directions should pergola purlins be concerning the sun?

Pergola purlins should run east to west to create the most shade. Assuming you’re in the northern hemisphere.

The one exception being if the rafters are installed at an angle increasing their shadow creating abilities. Then ignore the previous two answers, angle the rafters like shutters, tilted away from the sun running east to west, casting their cooling shadow over your deck.

How large should a deck pergola be?

For logistical reason, large enough to allow ample sitting area below with room to move in between the post. Depending on the time of day and year, the cast shadow will only cool part of the deck. Hanging plants or lattice walls will increase comfort on the deck missed by the pergola’s shade, increasing the amount of shade.

Another option to increase shade is a curtain or retractable canopy attached to the deck pergola. Allowing you to adjust shade as the sun moves along the sky.

If you would like a larger discussion and explanations about rafters and purlins, here’s a link to  Ozco Building products article. They go into much more details and explanations.

Material options for a Pergola

There are many different material options for a pergola. Some of the more common are

  • Pressure-treated wood
  • Cedarwood
  • Redwood
  • Vinyl or Composite
  • Fibreglass

Personally, I prefer cedar pergola for several reasons. The biggest being a balance of maintenance and cost. A wood structure with many hard to reach piece becomes very hard to refresh paint or stain. Cedar by nature holds up better under the sun and rain. So even if you don’t stain it again after assembly, it will last many years. Cedar is also naturally insect resistant

Vinyl, composite or Fiberglass are good for no maintenance but are more expensive. 

Related Pergola Questions

Do pergolas add value home?

Yard improvements roughly have a 50-80% return on investment. Pergola should be roughly the same. But its really more a question will a pergola make your deck more enjoyable to use during hot summer days?

How much will it cost to build a pergola?

An 8’ x12’ cedar pergola kit from Pergola Depot material will be around $3100 US.

A Trex composite low maintenance 10”x10” pergola kit about $5 500 US.

HomeAdvisors estimates material alone for a cedar pergola at $3 000.

Of course, these are all just material. Tools and labour will be required, either your own or hiring a professional to build a pergola for your deck.

These kits are all four-post designed, which raises the question.

Can a pergola be attached to House?

The simple answer is yes. A pergola can be a ledger of your house in the same fashion as a deck ledger. Unfortunately, in some jurisdictions like Calgary, Alberta, the city then views it as a house addition requiring a much more elaborate permitting process. Where a freestanding pergola doesn’t even require a permit, check with your local authorities before you start of requirements and limitations with pergolas.

And last, Does a pergola require a permit?

Permit requirements vary according to jurisdictions. In Calgary, pergolas do not require a permit if under 107 square feet.

What is the point of a pergola? Shade and many other things. If you would like to read more about pergolas, here is a link to Foreverwoods, which has a great article with many pictures.

Ryan Nickel

A Red Seal carpenter, passionate about building decks to be enjoyed.

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