When properly installed, asphalt shingles are extremely durable, but even the highest quality shingles need to be replaced eventually. If you’re like most people, a myriad of questions are bouncing around in your head.
- Should I tear off the old shingles or just roof over them?
- How do I select the right type of shingle for my home?
- What important details of the replacement and installation do I need to know?
If you feel a little unsure of yourself, you’re not alone. Roofing repairs and roof replacements can be confusing and sometimes very complicated. There are a lot of elements that come in to play during a roofing project.
Our DIY guide is designed to reduce confusion. We make it easy for you to first decide whether or not DIY roof replacement is for you, and if so, how to get it done safely and efficiently.
First and foremost, you’ll want to familiarize yourself with a few basic roofing terms and concepts. Roofs come in all shapes and sizes. Some are more difficult to replace than others, whether due to slope or complexity, so understanding every aspect of your roof is the first step in deciding whether or not you’re up to the task of replacing it on your own.
As you know, there are all kinds of roofs out there. The most common types are:
But there’s much more to a roof than just the type. There are various elements that make up a roof, and these elements can pose as minor obstacles when it comes time to re-roof, so it’s important to have an understanding of what goes into a proper one.
Anatomy of a Roof
- Roof over — Applying a new, additional layer of shingles on top of an already existing shingle roof. Typically, the maximum number of layers allowed is two.
- Roof replacement — Removing an existing shingle roof before installing a new one
- Square — Amount of roofing material needed to cover 100 sq. ft. (Ex. A 1,500 sq. ft. roof would require 15 square of roofing material)
- Slope — (also referred to as pitch) The angle of a roof; a roof with a 4/12 slope drops 4 feet in a 12 foot run, while a 12/12 roof is at a 45-degree angle
- Deck — Wooden board used to support the roof, spans the framing joists/trusses
- Flashing — Roofing material or metal used to cover intersections of the roof with vents, skylights, chimneys, valleys, all vertical surfaces, and any change in the roof’s direction
- Valley — The internal angle where two roof planes meet
- Ridge — A roof’s peak; the top intersection of two roof planes
- Eave — Overhanging lower edge of a roof
- Rake — Overhanging pitched edge of a roof; also refers to the board/molding placed along the side of a gable roof end
- Drip edge — (also referred to as a gutter apron) A metal strip installed along the edges of a roof to direct water away from trim and gutters
Roof-Over vs. Replacement
Chances are if you’re reading this, it’s because you’re well aware of the fact that your roof is in need of more than just a few simple repairs.
However, many people don’t realize that replacing their entire roof isn't the only choice they have. Installing new shingles, metal or other lightweight roofing option over the existing roof is typically an option as well.
Most building codes permit two layers of asphalt shingles on roofs with a 4/12 slope or less, while some allow three layers on steeper roofs.
If all of the following are true—and your building codes permit it—then consider roofing-over instead of replacing.
- There is only a single layer of shingles already on your roof.
- The sheathing has no damage; if the damage is minimal, it can be repaired/reinforced.
- Your roof’s structure can support the weight of another layer of shingles.
Consider the Costs
In addition to the time and effort you’ll save by not having to tear off your existing shingles, there are several ways roof-overs can save you quite a bit of money, too.
- Not having to lay down a new layer of underlayment can save anywhere from $20 - $100 per square.
- Roof-overs require less tools/equipment than complete replacement, eliminating the need to rent/buy them.
- Because your roof's structure won't be exposed, there's no need for extensive weather protection.
- With no shingles to dispose of, there is no need for a dumpster, and there are no disposal fees.
- There is less risk of property damage.
Average costs for a typical 2,200 - 2,600 sq. ft. roof (would require 22 - 26 squares):
Replacement (tear off)
- DIY: $3,000 - $6,000
- Pro: $6,000 - $12,000
- DIY: $1,000 - $4,000
- Pro: $3,000 - $7,000
The Importance of Inspection
Because there’s more to a roof than the eye can see, it’s important to have a certified roofing expert inspect your roof, even if you don't plan on having a pro do the work.
The last thing you want is to be up on your roof when the sheathing underneath is water damaged and failing. A certified roof inspector will be able to tell you if the roof is structurally sound, whether your home can withstand the weight of an additional layer of shingles, and how many layers currently exist on your roof.
They’ll also be more than willing to give you their expert opinion on whether or not a re-roof is the wiser decision.
Choose the Right Shingle
As the most common roofing material, shingles come in all different varieties, but the two most common types are:
Also referred to as a strip shingle, these are the most commonly used asphalt shingle.
They are made up of three segments, called 'tabs,' with a small slot on its lower edge used to connect to other shingles.
Also referred to as a 3-dimensional shingle, architectural shingles are made of several layers of material, giving it a texturized appearance.
Depending on your budget and desired outcome, you may want to go with a standard, 3-tab shingle, or you may be interested in a more eye-catching architectural shingle. Whatever style or price point you’re looking for, it’s out there.
Do not install new shingles over existing architectural shingles. Because of their texture, and how they don't lay flat, it's best to tear off old architectural shingles before installing the new shingles (or other roofing option).
Here are a few of the most common brands to help get you started:
Assemble Your Team
Rome wasn’t built in a day, and the same can be said for roof replacement, too. Whether you’re simply roofing over your existing one or replacing it entirely, you’re going to want to ask a couple of buddies to help out.
First of all, when it comes to tearing off your roof and replacing it completely, the longer it takes you to do so, the more your home is at risk of being damaged by inclement weather. Even with a team of 3 - 4 people, you’re looking at a minimum of 2 - 3 full days of work for a full replacement.
Not only that, but roofing is dangerous work, and having additional help is always advised for safety reasons.
Before discussing necessary safety precautions, you first need to honestly ask yourself: Am I certain that I can safely handle this roofing project?
If you’re confident in your abilities to walk on a slope, lift heavy materials, and do manual labor at an elevated height for at least a couple of days, then keep reading...
Even if you’re DIY'ing your roofing project, you’re still going to need to get a permit (whether you’re roofing over or replacing it completely) to ensure your roof meets the minimum building code standards.
Getting the necessary permit(s) will help minimize risks, like structural collapse, fire, and issues that could result in expensive repairs, injury, or even death.
In areas that experience hurricanes or high winds, permit requirements may be stricter, so be sure to check with your local government agency. For most, this agency is the Building Services Department.
When inquiring about a permit, have the following on-hand:
- Proof of property ownership
- Permit application (provided by local agency)
- Statement of repair — states that you will replace the roof you remove to ensure the building remains up to code
- Any construction or elevation drawings
Preparation doesn’t stop at permitting, though. Once you’ve ensured your roof and home are structurally sound, you’ll want to start setting up a safe environment so you can get to work, and that means having the right equipment.
People often underestimate the importance of a comfortable and supportive pair of rubber-soled shoes. If you don't have any, get some so that you don’t slip and slide off those sloped shingles.
You’ll also want a sturdy ladder set up at a safe angle (think a 4:1 ratio), firmly footed on the ground. Not only that, but make sure you secure the ladder to your home if you don’t have someone at the bottom to prevent it from slipping out. It’s never fun getting stuck up on your roof.
If your roof is sloped, you’re going to need an adjustable roof bracket or two, or at the very least a handful of 2 x 4s to use as makeshift steps. These allow roofers to reach the higher parts of a roof, while also giving them a flat surface to stand on.
WARNING: Never attempt to do roofing work in sub-par conditions. Wind, rain, and cold weather are not a roofer’s friend. However, even in good weather, roofs can be dangerous. Using a roofing safety system, like a harness, is always recommended on sloped roofs.
Rent a Dumpster
If you’re simply roofing over your existing roof, renting a dumpster may not be necessary. But if you’re planning on tearing off the current shingles before tacking on another, you’re going to want to rent a dumpster.
Not only is it a cost and time effective alternative to hauling the shingles out to the dump yourself, but renting a dumpster also minimizes mess.
A professional dumpster company will be able to position a 10 yard dumpster conveniently close to your house, allowing you to land a majority of the debris—like sharp nails and flashing—in the dumpster rather than your yard.
Become a dumpster rental expert with our user-friendly resources:
Option #1: Replacement (tear off)
1. Remove existing shingles.
Use a shingle scraper, pitchfork, or flat shovel to get under the shingles, prying them up from the roof.
A majority of the nails should come up with the shingles, but if they don’t, go back and pry them out with the split end of a claw hammer or prybar.
Sweep off any pieces of shingle still on the roof.
2. Secure loose boards and cover large holes.
Hammer down any boards or nails that have come loose, ensuring the sheathing is secure.
If there are any holes large enough to fit your finger through, cover them using aluminum flashing.
Smaller holes can be sealed using roof caulk.
3. Install underlayment.
Starting at the bottom corner of the roof, lay a strip of roofing felt horizontally across the bottom edge of the roof. Using a staple gun or hammer tacker, staple 6 to 8 inches apart, making sure there are no ripples or bubbles in the felt as you go.
Continue this pattern, moving towards the top of the roof, slightly overlapping each strip so there are no gaps.
TIP: If you’re roofing a structure that has heat in an area that snows or freezes, consider attaching a rubber membrane rather than felt. This adds more extensive waterproofing, which is important when melting snow or ice is a concern.
4. Mount standard drip edge flashing.
Line up a piece of drip edge flashing horizontally along the edge of the roof. The edge that curves out should be hanging over the edge, with the flat edge resting on top.
Mark where the drip edge lines up on the felt on both sides of the roof, then set the drip edge aside.
Using a tape measure, measure 3/8 in. (~1 cm) down from your initial marks, and make a new mark. Then, using a chalk line, snap a line along your newest marks. This is where your drip edge will go.
Take your piece of drip edge, line it up with your newly marked line, and nail it down using galvanized roofing nails. Repeat this until the entire edge is covered in flashing, making sure to overlap the joints slightly so that water running downhill will pass over the joint rather than under it.
You’ll likely have to trim the last piece of drip edge so that it fits your roof properly. After carefully measuring out the length needed, cut the drip edge using tin snips, but make sure you angle your cut to match the corner edge of your roof.
NOTE: Jutting the drip edge out slightly prevents water from coming into contact with the fascia board, which can lead to water damage. You also will want to install drip edges along eaves and rakes. (See Anatomy of a Roof)
To be sure your shingles don’t end up uneven and crooked, you’ll want to find the centerline of your roof.
Using a tape measure, measure equal parts on either side of the roof and then split the remaining length to find the middle.
Measure 10 ft. from the left edge of your roof, and make a mark. Measure 10 ft. from the right edge of your roof, and make a mark. Then, measure the distance between the two marks and split it down the middle. This is your roof's center point.
Once you’ve found your center point, hammer a nail into the roof to mark it, leaving the head slightly exposed. Then, using what’s known as the “3-4-5 method,” place the end of your measuring tape on the nail and measure 4 ft. straight to the right of your centerline mark. Hammer a nail into that spot to mark it, leaving the head slightly exposed.
Then, place the end of your measuring tape on the 4 ft. nail and measure 5 ft. up and to the left, using chalk to mark a small angle straight above your center point nail.
Next, place the end of your measuring tape on the center point nail again, and extend your measuring tape straight up 3 ft., marking where it intersects with the 5 ft. arch.
The line made between these two points (mark this with a chalk line) is perpendicular with your drip edge and is going to be your reference point for each row of shingles.
The first row of “starter” shingles will go over top of the drip edge, so for 3-tab shingles, you’ll want to remove the tabs on these using a utility knife.
Once the tabs are removed, find the slot located in the center of the shingle and line it up with your centerline, extending the bottom edge of the shingle (the edge with the line of adhesive) about ¼ in. past the drip edge. This will offer added water protection.
Once you’ve tacked the shingle in place, remove the tabs from the next shingle and align it directly next to the first, lining the new shingle flush against the edge of the last. Repeat this process until the entire drip edge is covered.
Just like the drip edge, you’ll likely have to trim the shingles to fit the edge of your roof properly, so do this only after measuring carefully.
The next row of shingles (with tabs attached) goes on top of the line of tab-less shingles you just tacked over the drip edge.
Just like the first line of shingles, you’re going to extend this row ¼ in. beyond the edge below to offer even more water protection.
To make sure you continue to install these shingles in a straight line, you’ll want to measure and mark the line of the intended installation.
- Figure out the dimensions of your shingle (commonly 36 in. L x 12 in. H)
- Using your measuring tape, extend up from the starter shingle (accounting for the height of your next shingle and the ¼ in. extension), and mark where the upper edge of the shingle should be attached.
- Make these marks on both ends, and snap a chalk line.
Then, take your first shingle and line it up with both the centerline and your newly snapped horizontal line, tacking it into place along its adhesive line. By tacking/nailing the shingle close to the tab slots, the likelihood of the shingle lifting away from the roof is minimized.
Follow the same pattern you did for the first line of starter shingles, lining up the shingles so the edges are flush and going all the way across, trimming the final edge pieces as needed.
From here on out, you’re going to want to leave 5 in. of shingle visible when tacking on the next layer. For shingles with a height of 12 in., if you leave 5 in. of the shingle underneath showing, that leaves 5 in. of overlap on the top shingle.
Because of this, you can measure up from the line of shingles you just installed in increments of 5 in., making marks as you go. Make these marks on either side of the roof, and snap a chalk line at each 5 in. point so that you have horizontal lines extending up your roof every 5 inches.
Because you want the roof to be as watertight as possible, avoid allowing the slots/joints of the shingles to line up from row-to-row.
An easy way to do this is: From the top portion of your roof, measure out horizontally from the centerline, marking each 6 in. increment.
From there, extend a chalk line from the top, innermost 6 in. increment mark to the bottom line of shingles. The chalk line should be centered in the middle of the innermost shingle tab. Snap a line there, then move over another 6 inches, lining it up so that the chalk line is centered within the slot. Do this across the entire roof, making vertical chalk lines every 6 inches.
This will set you up for smoother project completion. From here, you can simply line up the shingles in an offset pattern, tack them on, and crank out the rest.
NOTE: If your roof is sloped, you’ll likely need to adjust your roof bracket at some point in order to reach the top of your roof. Be cautious when doing this, taking care when placing the brackets so that any nails go into a rafter. (You can verify this by sound, just like checking for a stud in a wall.)
Once you’ve reached the top of your roof, the final shingle layer will likely extend past the top of the roof. Tack it along the adhesive line near the tab slots as you normally would, but also allow the remainder of the shingle to fold over the top of the roof, and tack it down on the other side, too.
9. Install the ridge cap.
Ridge caps are just pieces of shingle trimmed to form a 12 in. x 12 in. square. These squares are then layered along the edges of the roof, protecting the exposed crease from water damage.
Snapping a chalk line along your ridge’s edge as a reference point is a good idea. You want to be sure the ridge cap is perfectly centered, so start at the bottom, making sure each ridge cap shingle is evenly attached at the adhesive line on both sides of the ridge. Work your way up, slightly overlapping them as you did with the other shingles.
Option #2: Roof-over (install new roofing over existing roof)
1. Clean up the roof.
You don’t have to put in a ton of elbow grease here. The goal is to sweep the roof clear of any discernable debris so that you have a smooth surface to work with.
2. Attach new underlayment.
Once you’ve established that there are no leaks or major repairs needed, you want to decide whether or not you think you could benefit from another layer of underlayment.
This is not always needed, especially if a roof is still in good shape. However, an additional sheet of underlayment is a good idea in roof valleys, near eaves, and where water might collect.
Tack down the underlayment so that it’s smooth and doesn’t have any bubbles.
3. Remove ridge caps.
Okay, so you’re not leaving all the shingles on. Removing all ridge cap shingles before laying down a new layer will help the re-roof look its best and last its longest.
Use a flat pry bar or roofing shovel to remove just the ridge shingles, including all nails.
4. Replace damaged flashing.
Flashing around air vents, pipes, and valleys may need to be replaced, so double-check their condition. Unless they look like new, it’s best you replace them.
If replacing valley flashing, avoid driving nails within 6 inches of the valley’s center.
5. Mount new drip edge flashing.
Re-roof jobs call for new, U-shape flashing. Install the eave piece first; then install the rake piece, overlapping the eave flashing slightly.
Installing this new flashing—and nailing them down at high points—will further protect your roof from leaks.
6. - 9. See Above
For steps 6. through 9., see the instructions above for how to:
- Find your roof's center
- Attach the first line of shingles
- Install the second line of shingles
- Attach the rest of the shingles
10. Safeguard all flashing.
As you go, make sure all flashing is adequately protecting any plumbing vents, roof vents, skylights, chimneys, etc. before laying new shingles down over them.
Apply roofing cement under the flashing to help keep water out, and cut shingles to fit where they’re needed.
When you hit a chimney or sidewall, use step flashing—apply a shingle, then a piece of flashing—repeating as necessary so that water runs over top of the shingles rather than under them.
11. Install the ridge cap.
Ridge caps are trimmed pieces of shingles that form a 12 in. x 12 in. square. These squares are layered along the edges of the roof, protecting the exposed crease from water damage.
Snapping a chalk line along the ridge as a reference point is a good idea. You want to be sure the ridge cap is perfectly centered, so start at the bottom, making sure each ridge cap shingle is evenly attached at the adhesive line on both sides of the ridge. Work your way up, slightly overlapping them as you did with the other shingles.
Dispose of the Debris
If you thought ahead and rented your dumpster before starting the roofing job, all you’ve got to do now is check the area for straggling bits of debris (a magnetic nail sweep works efficiently), toss them in the dumpster, and call the rental company for pick-up.
But if you decided to go full on DIY and haul the shingles to the dump yourself using a trailer (or you waited until now to rent a dumpster), then you’ll have to clean up your yard—carefully.
Pay particularly close attention to driveways and areas that children play.
Watch out for nails, staples, and other roofing shrapnel. If you were haphazardly tossing shingles to the ground during the tear-off process, you could end up finding debris as far as 20 – 30 ft. from the site.
Once cleanup is completed, enjoy your new roof!