Dan is a licensed electrician and has been a homeowner for 40 years. He has nearly always done his own repair and improvement tasks.
Building a Covered Deck With a Connected Roof
Building a covered deck next to your home can add a great deal to both its value and to your enjoyment of it. The deck shown above is just such a project, and while this article cannot give you specific plans, it can help with planning and building your own deck, complete with roof for those rainy days.
Every deck plan must operate under some limitations. The location is generally pretty well set by other factors, and often the size is as well. In the case to be described here most of the deck itself was already in place, being used to support an old hot tub that had died a couple of years ago, and a new plan was needed for the existing deck. It was a little small and built right next to a garage in order to have power for the hot tub, but within those limitations, almost anything was possible.
As the deck is against another building, the roof is of major importance, and it was there that the actual planning began. Before we look at that, however, let's take a look at the actual deck itself, and what was done to improve it into something more suitable.
Step 1: Build and Add to the Original Deck
Our original deck was 10' X 8', just large enough to hold the hot tub, but that is a little small for a deck to relax on. It was decided to extend the deck out to a 10' X 12' area, using the same construction methods as the original
The deck was constructed entirely of 2X6 lumber, both treated and untreated. It was set on pre-formed concrete pillars (shown in the photos below) that had been dug into the ground and carefully leveled. A pillar was placed at every corner, with an additional pillar in the center of the 10' direction, giving a maximum spacing of 8' between pillars.
An additional three pillars were placed then, one at each of the new corners and one in the center of that run, again digging down until the resting surface for the lumber was exactly level with the rest of the pillars. Care was taken not to over dig the holes; doing so will result in soft, refilled dirt to support the decking, and it will inevitably sink.
Undisturbed soil, with perhaps ¼" of leveling sand, is needed at the bottom of the hole to support the concrete pillars. This method worked well for the 8 years, or so the hot tub sat there, and hot tubs are heavy when filled with water, there is no expectation of further settling. The original pillars were set at such a depth that the bottom of the 2X6 lumber was just above ground level to help prevent rotting, but treated lumber was used for all joists even though not in contact with soil.
The original rim joists and headers were all treated lumber, and the same thing was used for the new rim joist and headers as well as all joists. The original deck had joists on 16" spacing in order to support the massive weight of the hot tub, but the new section was built on 24" spacing and is more than adequate for ordinary foot traffic. The actual flooring material on both original and added sections is untreated 2X6 lumber, sealed with two coats of water sealer.
With the deck surface completed, it was time to take a look at the roof, and just what was to be done with it, as there are always options.
Step 2: Design the Deck Roof
This is where the real planning began, as the design of the roof would drastically effect the appearance of the finished deck.
Freestanding vs. Connected Roofs
Covered decks can be made with either stand-alone roofs or, when the deck is adjacent to a building, with a roof connected to the building. A stand-alone roof could have been constructed but would have looked decidedly odd next to the garage but not a part of it. Some kind of roof line attached to the garage would be needed.
Why Not Use a Lean-To Roof?
The simplest method, and one that would work well against a two-story house, is a lean-to type of roof. Simply put a couple of posts in the corners of the deck farthest from the building, with a header between them, and add rafters up to the roof of the building or attached to a ledger fastened to the wall of the building.
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In our case, however, the roof of the garage was only 8' above the deck; to continue the same 4/12 slope of the roof would have resulted in a roof that was only 5' above the deck at the far side. Not acceptable, particularly as that was the side of the deck where it would normally be entered from. At the same time, the garage roof pitch of 4/12 needed to be maintained as asphalt shingles require that as a minimum pitch. The decking rafters could be extended up the roof, but would have had to be 3' higher than the peak of the garage roof! Again, not acceptable.
Another option was to make a lean-to roof, covered in roll roofing. This would allow a lower pitch and keep the lowest point of the deck roof at least 7' high. The appearance, though, would not be good; the garage was to be redone with new shingles at the same time, and the difference between the two would have been striking.
How We Settled on a Regular Roof With a Ridge Extension
The final answer was to build a regular roof, with a ridge extending onto the garage roof. With a width of 12' and a pitch of 4/12 that meant the ridge would have to be 2' higher than the eaves of the garage: half the 12' deck width is 6', which means a 2' rise. It also meant that the ridge of the deck roof would extend onto the garage some 6', which was fine. Exact measurements were taken (the deck was a couple of inches off of 12' wide), giving an exact height for the ridge, and construction was finally able to begin.
Step 3: Build the Deck Roof
Before any rafters could be made, a supporting structure had to be constructed for them to sit on. 4X4 posts were to be used at all four "corners" (the rear corners of the deck were under the garage soffit and were moved out and nailed to the edge of the soffit) but what kind of 4X4? Everything in the store was chewed to pieces and would hardly make a good surface for little hands to spin around as kids will do. Beautiful redwood posts were finally chosen, at twice the price, but have turned out very nice and are well worth the extra $30 paid for them.
Posts were attached to the decking right at the corner and over the concrete pillars in the front with metal plates. These are readily available and are nailed to the deck and then to the posts. The posts were carefully plumbed to be perfectly vertical, and temporary bracing nailed to the deck to hold them during construction.
2X6 lumber was again used to go from the post and through the garage soffit, enabling attachment to the garage rafters inside the garage. One of the posts turned out to be exactly on the rafter, requiring that it be moved 1½" to the side. Rather than move the post off of the header of the deck on that side, the top of the post was notched to move just the 2X6 rather than the post, see the pictures below for this detail.
The garage roof sheathing needed to be cut to permit these "wall plates" to be inserted as they were higher than the garage roof, but that was alright as it would allow the deck rafters to extend past them, providing an eave, while still matching the garage roof. See details in the photos.
A double 2X6 header was built across the two front posts to support the roof ridge, one 2X6 on each side of the post. Double 2X6's were set onto and through the header to actually hold the ridge, with one on each side of the ridge. At this point, the ridge can be set and extended onto the garage roof, but the far end must be cut at the 4/12 pitch the garage roof is to sit flat. Ours did not sit over a garage rafter, and additional 2X4's were scabbed between rafters inside the garage to offer additional support.
Two short pieces of 4X4 were added at an angle, one from each front post to the double header to add both strength and better appearance. The 4X4's were attached to the posts with bolts and nuts, with the nuts on the inside, sloped side.
Holes were drilled with a forstner bit just large enough for washers to fit into, and that produced a flat surface inside the angled wood for the nut. This keeps the nut end of the bolt out of sight, and away from little hands that might get cut on it. The bolt head on the other side was left outside the wood as reasonably flat, unobtrusive and safe.
With the roof framework up, it was time to cut and install the rafters, and this required some special cutting.
Step 4: Cut and Install Rafters
Cutting lumber and nailing it together is straightforward, but things change when constructing rafters. All the deck lumber, and the boards used to make the ridge and other framework for the roof, are cut at 90º angles, but the cuts on the rafters need to be made at the slope of the roof; in this case a 4/12 pitch or about 18º. The use of a speed square, a special square for roof work, will make the task much easier and they are not expensive.
The upper end of each rafter needed to be cut at 18º then so that it will fit square against the ridge. The lower end, sitting on what would be the top plate of a normal wall, needs to have a birds mouth cut into it to fit properly. The video below gives a good demonstration of cutting a birds mouth into the lower end of a rafter, and the photos show how it is fit and nailed into place.
Rafters were made out of 2X4 lumber; the span is only about 7,' and a 2X4 will carry the wind and snow loads fine at that length. Rafters were fastened on 2' centers, with one extra on each side of the roof located exactly above the front header as a nailing surface for sheathing to cover the front. Rafters were left long, in order that they could be matched exactly with the existing garage roof and cut to length after being installed (and this cut, too, needs to be at 18º). A 2X4 fascia was nailed across the ends of the rafters for a finished look on the eave of the new roof.
The rafters on the existing garage roof present another challenge. After removing all the old shingles on the roof, a chalk line was snapped between the point where the new roof and the old would meet, at the bottom edge of both and up to the very peak of the new roof. A 2X6 was laid flat on the garage roof, 4½" back from that line, and nailed through the sheathing and into the garage rafters. In that matter, the roofing sheathing, at a 4/12 pitch, will just meet the chalk line.
This rafter needs to cut the same way at the top, but the bottom side is different. There is no birds mouth, as it has the entire width of a flat 2X6 to sit on, but it still needs cut at the proper angle of 18º. In addition, this cut is a compound miter in that the wood is not only cut at an angle, but the saw blade is at an angle as well. The lumber is mitered in two directions at once; along the angle to match the new roof as well as the angle to match the existing roof.
Cutting a Birds Mouth Into a Rafter
Step 5: Finish the Roof
With the rafters all in place, it is time to lay the roof sheathing. OSB board, 7/16" thick, is normally used for roofs and works well for smaller roofs such as this. Lay the OSB so that the bottom edge matches the 2X4 soffit board and the upper edge just touches the piece from the other side. The sheathing should be fastened with 8d nails, spaced every 18" or so. The sheathing is preferably laid with the 8' direction along the bottom edge of the roof, not perpendicular to it.
Attach any drip edge to be used, cover the sheathing with roofing felt and the roof is ready to be shingled. With both a ridge and two valleys to receive roofing, it is beyond the scope of this article to give instruction; instead you are referred to this article where installing shingles on the same deck roof illustrated here is explained in detail.
Step 6: Seal or Paint the Wood
With the basic deck completed, it was time to add some value to it and to protect what was done from weather and water damage. The entire deck was cleaned thoroughly, and two coats of Thompsons wood sealer applied as protectant. The posts were also coated with the same thing, and all other wood outside the roof was painted. Beams, rafters, sheathing; all wood inside was left natural for the appearance, and being under cover will not suffer the same weather damage that the outside will.
Step 7: Add Electrical
Next was some lighting. The garage wall had an outlet on it; it was a simple task to add an outlet to the exterior of the wall, surface mounted rather than being set into the wall. A 2 gang weatherproof box was used, with electrical conduit being bent from that point, up the wall to a second box mounted under the eave. The second box was used to add a string of LED rope lighting around the deck, just under the roof. That single string supplies enough light at night to read by, and is the perfect solution to lighting the deck for night use.
Conduit was also run from the second box up to the ridge at the peak of the roof and out to the center of the deck where an exterior rated ceiling fan was installed for those hot summer days. If you like the idea of a fan, make sure it is rated for use outdoors; although the fan here was completely under the roof, and up into the peak as well, condensation from cooling nights will still destroy a fan that is not sealed against the weather.
The first, two gang, electrical box was used for both an outlet and to install a light switch. The single switch is used to turn on both the fan and the rope lighting under the theory that a quick glance out of a house window will verify that they are both off at night; the fan, high in the "attic" of the roof, cannot be seen from the house and could be left on for days otherwise. If lighting is desired, but not the fan breeze, the pull chain on the fan will still turn it off.
Step 8: Add a Fire Pit
Finally, a fire pit was added to the deck. An all-metal, propane-based fire pit with ceramic logs was purchased and set onto the deck. Considerable thought was given to the burning of wood or gas, but gas finally won out.
While a gas fire pit won't put out the heat that a wood one will, a fire pit producing anything over 20,000 BTU's will warm the area enough for any but the coldest temperatures. In addition, gas is much cleaner burning and the area where this was built often prohibits outside fires as a pollution control effort.
A gas fire pit is quick to light and doesn't need time to get going, which can be important if the deck is to be used for only an hour or so. There is no ash clean-up, and ashes don't get ground into the deck surface as a result. Either way, though, the fire pit has been a very nice addition to our new covered deck.
Materials Used for the Covered Deck
2X6X10' treated lumber
4X4X8' redwood posts
4X4X8' treated post
1 1/2 square
250 sq feet
4, 10' pices
2" decking screws