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how to attach a patio roof to an existing house

The patio roof is an excellent addition to any home. It can be a great place to relax, enjoy the outdoors and stay cool during the summer months.

A good-looking, durable patio roof can add real value to your property.

However, it may not be as simple as you think to install one on top of an existing house or building.

This article will outline some of the things that you need to consider before installing one yourself and help guide you through what parts are needed for this type of project.

Different Ways To Join A Patio Roof to an Existing House

Attaching a patio roof to the house is an important decision that requires careful consideration. There are many different ways and positions you can choose from, each with its own pros and cons.

Knowing which position suits your needs best will make attaching the roof easier in the future once you learn how.


how to attach a patio roof to an existing house

For one-story houses, it’s important not only where you put a patio roof but how we attach it as well – there are many different ways that allow more flexibility than just including rafters inside the house itself (which has its advantages too!)

The most common way is below eaves level because these roofs usually have two rafters already embedded within them

High Patio Roof

how to attach a patio roof to an existing house

Instead of installing your patio roof at eaves level, you can go higher than your current house roof and then just remove the house’s gutters.

The backchannel will be placed much higher than in the case of a typical above-eaves level installation and it affects a high patio roof instead.

To make for this difference, you’ll need to install transfer flashing or some other type of water sealant onto that channel as well which gives an extra couple centimeters worth of height so long as there is enough space below to accommodate another floor with band joists installed between them (which would normally run parallel).

Cement Colum Patio

how to attach a patio roof to an existing house

This is a brilliant way to attach your patio roof, and it may be the easiest thing you’ve ever done.

This technique of direct attachment to masonry walls gives an excellent look while providing protection from the rain!

Steps on How to Attach a Patio Roof to an Existing House

Tools You Will Need

Nail gunBlack roofing felt
Wooden beamsLag bolts
Wooden planksOriented strand board
Wooden rafterUtility knife
Roofing shinglesLedger

1. Installing First Rafter

how to attach a patio roof to an existing house

Attach the first horizontal rafter to the main beam. This is usually done by nailing or screwing it through the roof sheathing and into an upper support post on one end of the house, then using a crew-to-sole plate or another fastener at the opposite end.

If your home has no such posts, you will need to use joist hangers (for sliding beams) or bridging plates for fixed headers instead.

2. Second Rafter

how to attach a patio roof to an existing house

Nail another rafter in place next to it with its bottom edge even with that of the previous rafter’s top edge; this should create two small gaps between them where they meet at their tops.

Place additional horizontals every 16″ until you have enough spanning from side to side to cover the width of your patio roof.

3. Install Ridge Board

how to attach a patio roof to an existing house

Now you can install a ridge board, which is simply a flat piece of lumber that spans from one end to the other and provides support for rafters above it.

It should be installed with its bottom edge even with the tops of previously installed horizontals, but not resting on top of them; this will allow room for insulation underneath.

If there’s insufficient space between beams or posts for either hanging or bridging plates, skip this step (it won’t be necessary) and proceed to the next horizontal rafter installation steps below instead.

4. Install Horizontals

Nail in place additional horizontals every 16″ across the opening until they cover an area equal to your desired lengthwise dimension plus 12″. You’ll need to install enough of these for a length equal to the width plus 12″ and then cut them off.

Cut the horizontals at your desired length and nail in place, continuing with every 16″ spacing until they cover an area that is also wide enough (equal to your roof’s width plus 12″).

You’ll need to finish by attaching any needed end rafters as well as nailing down side-rafters on all four sides; this will provide additional support for sloped portions of the patio roof.

If you’re installing a gable overhang or other more complicated configuration, consult building code requirements before proceeding.

5. Seams

Measure twice, measure once again when cutting so there are no “kinks”. Nail securely together.

6. End rafters

how to attach a patio roof to an existing house

Measure the distance of your house from ground level where you want to attach the roof. Add 12″ as recommended by code officials, and cut two end rafter boards at this length each.

Attach these with a nail gun or screws (be sure not to hit electrical wiring) before installing ridge board if necessary; otherwise, proceed directly to attaching side-rafters below without an additional step for end rails.

7. Side Rafters

how to attach a patio roof to an existing house

These are usually spaced out evenly on all four sides, which helps keep the weight balanced while providing stable support for sloped portions of patio roofs made with either metal or wood materials that may be more likely to warp over time due to exposure to harsh weather conditions.

They’re also designed so there are no gaps in the center of the roof, which would allow precipitation to accumulate and eventually leak through.

8. Side Rafter Attachment

Measure from ground level to where you want your rafters attached on either side of your home (or as instructed by building code officials).

Cut two boards at this length each before nailing them into place with a nail gun or screws; be sure not to hit electrical wiring while doing so.

You may need additional support for sloped portions if using metal materials like aluminum, but that will depend upon what type is used as well as its thickness.

Proceeding directly from attaching side-raiders without an additional step for end rails should work just fine for most types and thicknesses of patio roofs made out of wood material.

9. Side Rafter Overhang

Measure the length of your roof’s overhang (from outer edge to outer edge) and cut two board lengths that correspond – one for each side.

Nail in place with a nail gun or screws before proceeding, as this will help provide additional support around sloped portions at top corners if using wood materials like cedar..

10. Attaching Gable Fascia/Overhangs

The spacing used for attaching gables varies depending on the type of house you have but is generally set to match rafters so there are no gaps between them.

This also makes it easier when installing asphalt shingles later because they won’t slide off due to the lack of “gaps” underneath where water can collect. Follow instructions for your particular house and then proceed with installing the gable fascia or overhang as well.

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Things To Consider Before You Join Your Patio Roof To Excising Roof

Building Codes

Make sure you don’t forget to get that building permit from your local government before starting any changes. Being caught without it can cost a lot of money in penalties!

Patio Roof Design

The weight of your roof will have a huge impact on how it is built. You’ll need to be sure that the materials you use can bear any type of addition, from snowfall and ice build-up to extensions like solar panels.

This includes dead loads (the actual weight) and live loads (anything else).

Patio Roof Slope

You’ll have to make sure your roof has enough pitch for the type of extension you are choosing, as well as all manufacturer restrictions.

When attaching a patio roof to an existing house, ask yourself if it complies with any limitations set by the company that manufactured it or other factors such as zoning regulations and building codes in the place where you live.

Patio Rafters

Building a roof for your home is an important task. It can be difficult to figure out how much lumber you need without help, but there are online calculators that will do all the work of figuring it out!

For example, The American Wood Council has created a SPAN CALCULATOR which makes calculations easy and fast


If you live in a colder area, the frost line needs to be taken into account when figuring out footings.

The International Building Code and local building codes are great resources for determining how big your footing should be depending on what level of protection against cold weather is required by code.

Support Columns

If you want to make your patio roof extra safe, then you add support columns. The easiest way to do this is by adding one in the two corners of the house furthest from the walls and then constructing a frame and attaching it with brackets and screws.

Covering up these frames with whatever material will work best suits your preferences should be easy enough!


Flashing will keep water away from the ledger board when attaching your new patio roofing material onto an existing house– this step often gets overlooked!

Don’t forget about bending down metal sheeting over the edge of where it meets up at the wall for protection against moisture and potential future leaks.


A patio roof installation is a great way to add space and enjoy the outdoors even more! When you’re ready for an expert opinion, we are here to help with your project. Let us know if there’s anything else we can do to help make this process easier or faster!


Meet Bob Vil, is a seasoned patio enthusiast and the author behind the informative and engaging content on our patio website. Bob Vil has a degree in Civil Engineering (BSCE). With over a decade of experience designing, building, and maintaining patios, fire pits, and porches, Bob Vil is an expert in all things outdoor living. Throughout his career, Bob Vil has worked on a wide range of projects, from small, intimate patios for residential clients to large-scale commercial installations. His knowledge and expertise have helped countless homeowners create beautiful and functional outdoor spaces that they can enjoy for years to come.

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