How To Add Slope To Pergola Roof?


Slope is a common structural addition to most patio installments. It adds an angled surface to the structure, which allows rainwater, snow, and every other unrequired material to slip off the roof naturally. While the roof of a pergola isn’t frequent, adding a slope on top of that can be a tricky job to do. Also, as most people tend to do such works DIY, a common question of how to add slope to a pergola roof remains.

Now, if you have a pre-existing pergola with or without a solid roof and you want to add a slope to that, then you have undoubtedly found the right content. There is more than one way to add a slope to a pergola roof, and it varies from pergola to pergola depending on size, design, and many more factors. So continue your reading to learn the latest version of how to add slope to a pergola roof, what the considerable factors are, and how to maintain your slope-raised pergola properly. A slope-attached pergola in your backyard, at ease.

5 Ways To Add Slope To Pergola Roof

Adding a sloped roof to your pergola is a simple way to add style and interest. There are various professional and DIY ways to add a slope to a pergola roof. We have listed the top 5 of them based on ease of work, methods maturity, efficiency, etc.

1. Modified Rafters

Modified Rafters

Once you have the angle, you can cut the rafters at that angle. Then, it’s simply a matter of attaching the rafters to the pergola. You can do this with screws or nails.

Adding modified rafters to your pergola roof is one of the easiest ways to add a slope to it. Rafters are horizontal timber frames that help the pergola’s roof remain in shape. There are two slightly different options to modify the pergola roof rafters.

  • Install additional angled rafters over the existing roof.
  • Replace some of the existing rows with modified ones.

In both ways, first you have to identify the perfect slope angle for your pergola. For that, you have to measure the height and width of the pergola roof and calculate it manually or put the data on a trustworthy online slope calculator to figure out the end-to-end height velocity.

For the first option, take some 2×8 or 2×10 timber that has the length to cover your pergola roof width (downwards the slope). Measure and mark a line through the timber based on the slope angle you have figured out. Using the cutting saw, cut the timber in halves through the middle with precision. Place each piece of timber above the pergola with nails or nuts and bolts. Place weather-resistant polycarbonate or stainless steel roofing above the pergola.

For the second option, carefully assess your pergola’s existing rafter formation. Upon close assessment, you will be able to identify which rafter needs to be replaced with a modified rafter. Cut sections of the rafters using a saw or remove them completely. Now, as per your desired angle, cut new rafter sections to match the desired slope. Attach these new rafters in the blank positions using screws or nails. Make sure they are securely fastened and aligned with each other.

2. Adjustable Mounting System

Adjustable Mounting System

Attaching an adjustable mounting system is another method to add a slope to a pergola roof. These mounting systems create an angled pitch on the pergola roof and add slope effects to it. You can also add them over base pillars to raise their height. Here’s how you can do it:

  1. Start by measuring the existing height of your pergola posts. Next, determine the desired angle or pitch for your sloped roof. Use a level and mark the new height on each post accordingly.
  2. Install adjustable mounting brackets on the marked pillars or positions on your pergola roof. If you choose to raise the pillars, then install similar-sized brackets to make certain posts higher. If you choose to install them on the existing roof, then place the brackets in a sequence that allows you to create a slope angle from the higher one to the lower one.
  3. Attach the sloped beams to the adjustable mounting brackets. These beams will provide the necessary support for the sloped roof. Ensure that they are securely fastened and level with each other.
  4. Once the sloped beams are in place, you can proceed to install the roofing material of your choice. Secure the roofing material firmly to the sloped beams, ensuring proper drainage and water runoff.

3. Raising The Roof

Raising The Roof

Not all the pergolas are freestanding; some can be attached to your house structure too. Adding a slope to attach pergolas (arbors) is much easier than the free-standing ones. For that, you can raise the attached portion higher on the wall to create a slope angle towards the front. Its steps:

  1. Remove the pergola roof from your house wall completely or add a temporary pillar to hold it in place.
  2. Measure your pergola’s overall height and mark a new location on the wall based on your predetermined added slope height.
  3. Drill a hole in the marked spots to set an attaching bracket that will house your pergola beams.
  4. Attach the metal brackets or mounting system to the wall using screws, nuts, and bolts, and ensure a secure hold.
  5. Install the pergola beams on the new spots to create a slope angle towards the front.
  6. After installing the beams at a sloped angle, you can place your convenient roofing material on the angled pergola roof.

4. Adding Tapered Beams

Adding Tapered Beams

A tapered beam is a type of non-prismatic beam that has varying depth and/or width at its ends or mid-span. It is similar to the sloped wooden rafters mentioned in Method 1, although they come premade and hold more strength. Their installation process includes:

  1. Inspect the pergola roof structure and identify the place where the beams will be mounted.
  2. Measure the tapered beams as your pergola roof dimension and cut the beams to a selective size.
  3. Attach the beams over the marked roof spot and secure them with screws.
  4. Install the roof material with the newly added beams, using the necessary materials.

5. Adding Roof Ridge

Adding Roof Ridge

You can add an additional roof level to create a ridge-shaped roof on your pergola. This will create a double slope in the opposite direction and run off water faster. This installation will create a better aesthetic appearance for your pergola as well. You can install such a roof ridge over your existing pergola roof or remove the previous one to remodel your pergola roof with a slope. Its installation steps are:

  1. Detach all the possible wooden timbers of the pergola except the side beams. (This isn’t applicable if it goes over the existing roof.)
  2. Place a single 4×4 piece of hardwood timber positioned right in the middle of the pergola roofing and secure its ends with pergola beams.
  3. Note that the two slopes will be on opposite sides of the timber.
  4. Take 2×4 timber pieces long enough to cover the roof’s length plus 1 foot, and cut them in half from the middle.
  5. Place each of the pieces on the roof, one end on the middle timber and the other one on the side beam.
  6. Secure both of the ends with nails. Place all of the timber pieces on the two sides of the beam, one foot apart.
  7. Upon completing the placement of the timbers, place suitable roofing material that can be bent to allow installation without cutting through the middle.
  8. If the pergola is larger, opt for placing separate roofing pieces on two sides and covering the roof edge with similar material.

For proper implementation of this method, it is better to hire a professional if you are not that skilled with timber work.

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Factors To Consider For Adding Slope To Pergola Roof

There are a few important factors that you should be concerned about while adding a slope to the pergola roof. The outcome of the added slope is largely influenced by these factors:

  • Weather Pattern: Not all the geolocations have similar weather patterns and intensities. Understand your area’s weather pattern to determine how well the sloped rope should be integrated and the material that will be used. Go for sturdier methods if it is very windy.
  • Slope Angle and Direction: The slope angle is important to run off the rainwater properly. In general, ¼ of an inch per foot is ideal as a slope angle. But if it is a snow-prone area, then keep the angle more upright to run off the snow as well. The slope angle is usually kept in or back of the pergola.
  • Pergola Integrity: Remember that additional customization on the pergola to set the slope can easily weaken its overall integrity. So before jumping into anything, try to have a consultation with professionals or similar users for the better safety of the pergola.
  • Quality Roofing Material: When adding a slope to a pergola roof, using quality material is a must. Downgraded, cheap materials can weaken your pergola’s overall integrity and even raise the maintenance cost by falling apart soon. Timber and roofing materials should be weather-resistant and durable.
  • Easy to Install: When you are DIY adding a slope to your pergola, following the easy slope-adding method is convenient for you. That’s why, upon observing your pergola’s size and existing roofing structure, choose the method that’s easy to install.

Tips To Maintain A Sloped Pergola Roof

It’s not all done yet, even after a successful slope addition to the pergola roof. If you want to keep your sloped pergola roof durable and working, then you have to take some maintenance steps:

  1. Routine Inspect: You have to inspect the pergola’s overall integrity routinely. Look for any displacement, cracks, etc. understand the reason, and take measures to sort that issue out. Inspection can help you identify and prevent disasters early.
  2. Clean the Roof and Gutters: Roofs are subject to dust and sand materials that flow with air. These can create an obstacle to the smooth flow of rainwater, ultimately damaging the roof. That’s why the roof and gutters should be cleaned regularly.
  3. Sort Out Any Leakage Issue: Leakage can be a common issue due to weak structural integrity and a lack of quality material. But these leakages shouldn’t be allowed to get bigger. Even the smallest hole can cause the roof to totally disintegrate.
  4. Add Occasional Retouch: As part of your maintenance effort to keep the pergola roof working, you should retouch it with paint to endure its durability. Anti-rust-coated paints are very effective against harsh weather effects.
  5. Remove Leafy Trees and Branches: Fallen leaves are one of the biggest enemies of pergolas. It creates a mess in both roofed and unroofed pergolas. To ensure pergolas have better drainage capability, surrounding trees and branches should be trimmed off.

Final Thoughts

A pergola is usually a semi-open-roofed patio installation that allows its user to enjoy their backyard moments in touch with nature. But they can be further modified with a proper roof to save you from excessive sun, heat, rain, or snow. To get a better result from these roofs, adding slopes is necessary. There are various ways to configure a slightly tilted pergola roof. You can add height to certain pillars to make other portions lower, add adjustable sloping kits, and do some other things. But in every method you use, beware to keep the structural integrity intact. Immature slope addition can weaken your pergola structure, leading to high maintenance costs and reduced durability.

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I am Donald M. Beyer and I am backyard enthusiasts. I am a homeowner who has been doing DIY projects in and out of my house for many years. From simple backyard lunches to making an old-school pizza oven in my own backyard, I have a lot of experience in turning my backyard into my and my family’s personal playground.

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