Classic Porch, Boxboro MA

You’re looking at your deck and wishing it had a roof.  Shade from the summer sun would be welcome.  And protection from rain, so you and your family wouldn’t have to grab their dinner plates and scurry inside when a surprise shower surprises you.  Or watch your daughter’s chocolate birthday cake being destroyed by that sudden downpour.  Yes, a roof would be good.

Oh, and screens to protect your family from those nasty flying invaders who buzz and bite and harass everyone.  A porch would be nice, very nice.

However, the best place for a porch — really, the ONLY place for a porch — is right there, where your deck sits.  So you ask: Can I convert my back deck to a screened porch?  Lose that hot bug magnet and gain a cool, sheltered outdoor room?

Yes, you can. Well, to be more accurate: probably you can.  Converting a deck to a porch is often possible; it depends on a number of factors.

Let’s assume your deck is sound; that it is properly framed, has solid footings, has no rot, and is properly attached to your house.  (For a guide to quickly evaluating your deck, see my blog post about deck safety.)  Is your deck structure OK? Good, then let’s start planning.

First, look up. Imagine a new porch on your house. Will its roof attach to a house wall or to a house roof? Are there any obstructions – like windows, vents in the wall or through the roof, power lines, or skylights? You may need to move these.

                                                                      Porch Wall Tie-ins

OLYMPUS DIGITAL CAMERA       Levetin Wall roof lines ed


                                                                  Porch Roof Tie-ins

Deck for conversion, Burlington MA


Backyard deck

Roof and sidewall problems









How high is your deck off the ground?  Your new porch will likely require new footings and additional framing underneath. Is there space under your deck to install these?  Six feet or more would be good; four feet or less could pose real problems for conventional sonotube footings.  Can a man or machine get under your deck and dig the four foot deep holes your building code requires?

Tall deck for conversion, Lexington, MA

This deck is high enough

Low Deck, Framingham, MA

Too low


The shape and size of the roof will dictate where new footings are needed.  If your new porch will cover the entire deck, you may be able to angle the new footings along the deck edges.  Maybe.

Next, look at your deck.   Is it well-located for a porch?  Is there an access door from the house?  Will traffic flow smoothly from that room into the porch?  A kitchen to porch path is appropriate for dining on the porch.   A bedroom to porch transition rarely works well.

Is your deck the right size and shape for a porch?   If your deck is too large, you could convert part into a porch and keep the remainder as a deck.

Then, look around.  What shape does your house roof have now?  Gables are very common; hip and shed roofs are less popular.  How steep are the roof slopes?  Matching the shape and pitch of existing roofs will help your new porch to blend in architecturally and not look “tacked-on.”

Before conversion


Gable Porch, converted

Gable Porch, converted

Your porch side walls will meet your house walls.  Is there anything blocking those intersections?   Existing windows, doors, vents, outlets, lights, etc. may affect where the porch walls can attach and will impact the porch.

No major problems?  Great.  Let’s do it!

But before you grab that sawzall and start chopping your siding, let’s take a breath and plan all this out.  The shape and size of your porch determine the shape of the roof.   A long, shallow porch wants a shed roof.

Shed Roof Porch

A shed roof can be the easiest roof to construct.

A gable roof will accommodate a wide range of porch sizes and styles….

Gable Porch, Lexington MA Gable Porch, Lincoln MA Gable rood porch in Beverly - edited

Attaching a porch roof and new walls to your house is more complicated — and riskier — than just attaching a deck.  You don’t want your new roof to leak water into your home and start rotting the walls. Are there any wires and pipes hidden in the walls?  Just as your house foundation supports the deck, your house walls or roof will support the new porch roof.  That would be a few hundred pounds in the South or several thousand pounds in snow country.  Or maybe no weight at all, depending on what ceiling shape you choose.  Really?  A porch ceiling can add thousands of pounds to my house wall? Technically, no, but having ceiling joists can re-direct thousands of pounds of snow load away from your house wall.  It depends on what….Wait, wait “Ceiling joists?”, you ask.  You thought joists were in the floor.  They are, but your new porch may have joists in its ceiling too, joists that support no weight, but merely prevent the walls from collapsing — unless your porch has no joists in its ceiling, and instead has a ridge beam.

If all this seems complicated, that’s good.  It is.  Properly structuring a porch roof is complicated.  And that complexity is magnified by the risk: “thousands of pounds” and “collapse” and “rot” are serious words.  And they are aimed directly at your house.  If you cannot distinguish a rafter from a ridge beam, if you cannot calculate the tributary load that a roof beam imposes on your house wall, hire a professional.  Find a porch builder with extensive experience both designing and building porches, a company that can evaluate the structure of your existing deck and solve the roof load problems.

Before you ask that structural expert about your porch’s structure, focus on your expertise: how you will use your new porch and what furniture you want.  Those functional needs will help determine your porch size, and will help your porch expert design your new outdoor room.

Now you’ve reached the end of this little article, so let’s look at the bottom line:  How much ca$h can you save by re-using your deck?

Less than you might think.  On a simple porch, with modest materials and features, reusing a solid deck might save you 25%.  On a more elegant porch, with upscale materials and features, the savings will diminish to less than 20%.  Still, those dollars are noticeable.  But be careful: problems hidden in your deck structure can quickly chew into your savings.  Have a professional analyze your structure thoroughly before you count your dollars.

For more photos and information about porches, see A Pictorial Essay of Front Porches and 6 Kinds of Porches for Your Home.

At Archadeck of Suburban Boston, we offer professional design and build services for clients west and north of Boston. Over the past 26 years we have designed and built over 950 projects, including over 240 porches. We have enhanced the depth of our expertise by limiting our work to decks, porches, sunrooms, and patios. To view some of these projects or see our design and service awards, visit our website. To learn how we treat our clients, check our ratings on Angie’s List or read about us in an article in Remodeling magazine. For a free design consultation and a relaxed and rewarding experience, contact us via e-mail, or by phone, 781-273-3500

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