I’ve seen enough leaky roofs to last a lifetime, and most of the time, the culprit is something small but absolutely vital: the flashing. Specifically, I’m talking about the metal or plastic pieces that direct water away from vulnerable spots like chimneys, vents, and valleys. It’s a question that pops up more often than you’d think, especially when you’re staring at a pile of new tiles and a roll of flashing material wondering, ‘Okay, what goes first?’ The answer to whether are flashings installed before the tile is a resounding, no-nonsense yes.
You can’t just slap tiles on and hope for the best. That’s a recipe for disaster, and frankly, a good way to become very familiar with your local roofer’s billable hours. Getting this sequence right is a must for a dry house.
The Absolute a Must Order: Flashing First, Tiles Second
Look, I’m not trying to scare you, but I’ve been there. On a project a few years back, a buddy swore he could get ahead of schedule by laying some tiles around a vent pipe before fully installing the vent flashing.
He was so focused on getting those beautiful new terracotta tiles in place, he figured he’d tuck the flashing in later. Big mistake. Huge.
Within the first heavy rain, we had a tell-tale damp spot blooming on the ceiling below. It wasn’t a torrent, just a persistent drip, drip, drip that drove everyone nuts. Trying to pull up perfectly set tiles to properly integrate the flashing underneath was a nightmare. We ended up having to remove a whole section, re-do the flashing correctly, and then re-tile.
Cost us double the time and a good chunk of change. So, when you ask are flashings installed before the tile, the answer is an unequivocal, ‘YES, it’s the only way to do it right.’
The purpose of flashing is to create a waterproof barrier at specific points where the roof covering meets another element or changes direction. Think of it like a raincoat for your house’s vulnerable points. Water naturally wants to flow downwards. When it hits a seam, a joint, or an object protruding from the roof, it can seep into the underlying structure if not properly directed. Flashing is designed to catch that water and channel it away, typically onto the main roof surface where it can continue its journey down to the gutters.
Installing tiles first means you’re basically trying to build a dam after the water has already found a way around it. The flashing needs to sit underneath the roofing material at the important overlap points, creating a continuous, impermeable layer. This is especially true for ‘step flashing’ used along walls or chimneys. Each piece of step flashing is designed to overlap the one below it and lie directly on the roof deck, with the tiles then laid over it, creating a series of steps that water has to navigate. If the tiles are down first, you can’t get that proper overlap. You’re left with a gap, a vulnerability, and a future water problem.
Some builders might try to get clever and argue they can ‘integrate’ flashing later, perhaps by sliding it under existing tiles. This is a hack. It rarely creates a seal as effective as a properly installed flashing, and it’s a surefire way to invite leaks down the line. The integrity of your roof depends on this layering. It’s like building a sandwich; you wouldn’t put the top slice of bread on before the filling, would you? Same principle applies here. Flashing is the foundation of your watertight seal at these important junctures.
What to Look for: The Anatomy of Proper Flashing Installation
When we talk about ‘flashing,’ it’s not just one generic piece of metal. Different areas of the roof require different types of flashing, and understanding these is key to knowing when and how they should be installed. The most common areas are penetrations (chimneys, vent pipes, skylights) and transitions (roof valleys, hips, and where the roof meets a wall).
For vent pipes, you’ll typically see a ‘pipe boot’ or a ‘flashing collar.’ This consists of a rubber gasket that seals around the pipe and a metal or plastic flange that sits underneath the shingles or tiles. The process is straightforward: slide the flange under the shingles that are directly above the pipe, making sure it extends down the slope. Then, the shingles or tiles are laid over the flange.
The rubber boot then seals the gap around the pipe itself. If you install the tiles first, you’re likely going to have to cut a hole in them to get the flashing in, which is messy and compromises the tile’s integrity. (See Also: Can I Install A Transition Channel On Tile )
The flange needs to be integrated into the roof’s water-shedding system from the get-go.
Valleys are another important area. Roof valleys are the internal angles where two roof planes meet. They collect a lot of water and ice, so they need solid protection.
There are two main methods: open valleys and closed valleys. In an open valley, a metal channel (the valley flashing) is laid first, extending from the ridge down to the eave, and the two roof planes are cut to meet at its edges.
The tiles are then laid around this channel. In a closed valley, the tiles from both sides are woven together, with a layer of underlayment and flashing material installed underneath this woven section.
In both scenarios, the flashing is the base layer that the tiles are then installed against or around. You absolutely cannot lay tiles and then try to slide a valley liner underneath.
Step flashing is used where a sloped roof meets a vertical wall, like a chimney or a dormer. This is a series of L-shaped pieces. The bottom leg of the ‘L’ sits on the roof, and the vertical leg runs up the wall. Each piece of step flashing is installed under the shingle or tile directly above it, and the next piece overlaps the one below. Then, a continuous flashing piece, often called a ‘counterflashing,’ is typically installed over the top edge of the step flashing and attached to the wall, often embedded into the mortar. This is the most visually obvious example of why flashing must go down first: the tiles are laid over the step flashing.
My rule of thumb is to look for continuity. The flashing system should create a complete, unbroken path for water to travel away from the roof deck. If you can see any gaps or if the flashing appears to be sitting on top of the roofing material rather than under it at important junctures, it’s likely installed incorrectly. A good roofer will make sure the flashing integrates smoothly with the underlayment and the primary roofing material, providing that important first line of defense.
Common Mistakes That Lead to Leaks (and How to Avoid Them)
Mistakes in flashing installation aren’t usually subtle; they’re loud, leaky calls for attention. The biggest one, as we’ve hammered home, is the timing: installing roofing material before the flashing is properly seated. This leads to gaps where water can sneak under your tiles and into your attic or ceiling.
I remember a job where the crew was rushing to finish before a storm hit. They laid the shingles right up to the chimney base and then tried to tuck the flashing underneath. It looked okay from a distance, but the bottom edge of the shingles wasn’t properly turned up over the flashing flange. The first gust of wind and rain basically forced water right under the shingles and down the wall.
Took us a whole weekend to fix that mess.
Another common pitfall is using the wrong type of flashing or using it incorrectly. For example, using plain galvanized steel flashing in an area prone to salt spray or harsh chemicals is a recipe for rust and failure. Stainless steel or copper would be a better choice, though more expensive. Similarly, not extending the flashing far enough down the slope, or not having enough overlap between successive pieces of step flashing, creates pathways for water. The goal is always to direct water onto the next layer of roofing or flashing, not into a void. (See Also: Can I Install A Transition Channel On Tile Reducer )
Improper fastening is also a big deal. Flashing needs to be secured to prevent wind uplift and to maintain its position. However, you don’t want to over-fasten or place fasteners in a way that creates holes where water can easily enter. For instance, screwing directly through the main body of a valley flashing without sealing the fastener holes is a surefire way to get a leak. Usually, fasteners are placed in areas that will be covered by the next layer of roofing or flashing, and any exposed fastener heads should be sealed with roofing cement or a compatible sealant. But again, the goal is to avoid any unnecessary penetrations.
I’ve also seen builders skimp on the underlayment beneath the flashing. While the flashing itself is the primary barrier, a good quality roofing underlayment provides a secondary layer of protection. This is especially important in valleys and around penetrations. If the flashing were to somehow fail, the underlayment can often buy you time and prevent immediate damage. Skipping it or using a cheap, flimsy underlayment is false economy. It’s like putting on a bulletproof vest but forgetting the Kevlar lining – it’s better than nothing, but not as good as it should be.
Here’s a quick rundown of common errors and how to dodge them:
| Mistake | Why It Happens | How to Avoid It | My Verdict |
|---|---|---|---|
| Roofing Material Before Flashing | Rushing, poor planning | Always install flashing components first, making sure proper overlap and integration with underlayment. | Catastrophic. Avoid at all costs. |
| Incorrect Flashing Type/Size | Lack of knowledge, using stock parts inappropriately | Research specific flashing needs for your roof type and climate. Use manufacturer-recommended components. | Leads to premature failure. Don’t guess. |
| Inadequate Overlap or Sealing | Cutting corners, poor workmanship | Make sure sufficient overlap between flashing pieces and that all exposed fasteners or seams are properly sealed. | A magnet for leaks. Double-check everything. |
| Skipping or Skimping on Underlayment | Saving a few bucks | Use a high-quality underlayment specifically designed for roofing, especially in high-risk areas. | A vital secondary defense. Never omit. |
My Real-World Experience: The Tile and Vent Pipe Saga
I’ve always been a bit of a DIYer, sometimes to my detriment. About ten years ago, I decided to tackle replacing a few old roof vents on my garage. Seemed simple enough – cut out the old ones, put in new ones, slap some sealant around. I bought these nice, sturdy metal vent caps with flanges, thinking I was all set. The problem was, I got them home and realized the existing roof tiles were laid right up to where the old vents sat. My brain, bless its optimistic but often misguided heart, thought, ‘I’ll just lift these tiles a bit, slide the new flange under, and then seal it all up tight.’
So, I started gingerly prying up the tiles. They were old and brittle, and about three of them cracked before I even got the flange fully seated. I managed to get the flange under the ones that didn’t break, shoved a generous bead of roofing cement around the base of the new vent, and screwed it down. I figured the cement would handle any minor gaps. For a week, I felt pretty proud of myself, staring up at the shiny new vents. Then, the first real rain came. Not a downpour, just a steady, insistent shower. Within an hour, I noticed a dark patch appearing on the plywood sheathing inside the garage, directly below one of the vents.
Panic set in. I scrambled up into the attic space (which is cramped and dusty, by the way) and saw water trickling down the underside of the roof deck, right where the new vent flange met the tiles. The problem was exactly what I suspected but chose to ignore: the flange wasn’t properly integrated under the tiles. The tiles were acting like little channels, directing water onto the flange, and because it wasn’t seated correctly, the water found its way around the edges where I had slathered on that inadequate roofing cement. The cement sealed the top, but not the important underlying overlap.
Pulling up those tiles again was even worse than putting them down. More broke. I ended up having to remove a whole row of tiles, pry out the poorly installed flange, and then install new, proper flashing that extended under the overlying tiles. I also made sure the new flashing had a raised lip to prevent water from sitting there.
Then, I re-installed the tiles correctly, making sure they overlapped the flashing as designed. It took me an entire Saturday, and by the end of it, I was covered in dust, scratched, and thoroughly humbled.
That experience cemented in my brain the absolute necessity of proper flashing installation order. It taught me that ‘good enough’ when it comes to waterproofing is simply not good enough.
Contrarian Opinion: Can You Ever Really Get Away with ‘later’ Installation?
Now, here’s where I might ruffle some feathers. Everyone and their dog will tell you, unequivocally, that are flashings installed before the tile. And for the vast majority of situations, they are absolutely correct. It’s the industry standard, the building code requirement, and the only way to guarantee long-term watertightness.
However, I’ve seen a few instances, usually on very low-slope or flat roof sections where water doesn’t have much gravity to work with, where a skilled roofer might use a different approach for certain types of flashing. For instance, on some very flat roof systems, particularly those with a continuous membrane, a specialized flashing might be integrated into the membrane after the primary membrane is laid, and then a cap flashing is applied over it. This isn’t about sliding it under tiles, though. It’s more about sealing a membrane edge or a penetration in a system designed for low slopes. (See Also: Can I Install Tile Over Subfloor )
But here’s the important distinction: this is NOT what happens with standard sloped roofs and tile or shingle installations. Trying to ‘integrate’ flashing after tiles are down on a pitched roof is almost always a hack job, a shortcut that will fail eventually. The reason it’s so often stated as a hard rule is that for pitched roofs with overlapping materials like tiles or shingles, the flashing must be the underlayer. It needs to be there to direct water down and away from the joints and seams of the primary roofing material.
My contrarian take is this: while the rule is almost universally true for pitched roofs with tiles, understanding why it’s true is more important than just blindly following it. The ‘why’ is about creating a continuous, overlapping water-shedding barrier. If you can achieve that through a slightly different sequence on a system designed for it, then maybe, just maybe, you’re okay. But for 99.9% of tile roofs, the flashing goes down first. Don’t get cute. Don’t try to be a genius. Follow the established best practice. It’s established for a reason – to keep your house dry.
Faq: Your Burning Questions About Flashing and Tile
Do I Need Flashing Everywhere?
No, you don’t need flashing everywhere. Flashing is specifically used at points where the roof covering is interrupted or changes direction, creating potential weak spots for water intrusion. These important areas include where the roof meets walls (like chimneys or dormers), around any pipes or vents that penetrate the roof, in roof valleys, and sometimes along roof edges (drip edge flashing). The main expanse of the roof covered by tiles or shingles relies on the tiles themselves and the underlayment for waterproofing.
How Long Does Roof Flashing Typically Last?
The lifespan of roof flashing varies significantly depending on the material used, the quality of installation, and environmental conditions. Basic galvanized steel might last 10-15 years, especially in harsh climates, before rusting or corroding. Copper and stainless steel can last much longer, often 50 years or more, but they come at a higher cost. Properly installed flashing, regardless of material, will generally last as long as the roofing material it supports, or longer, if it’s not subjected to excessive damage or corrosion.
Can I Use Roofing Cement Instead of Proper Flashing?
Absolutely not. Roofing cement (or sealant) is a supplementary material used to seal small gaps, fastener heads, or to adhere edges of flashing or underlayment. It is NOT a substitute for flashing itself. Flashing is a structural component designed to channel water away. Relying solely on sealant would be like trying to patch a leaky boat with duct tape – it might hold for a little while, but it’s not a permanent or reliable solution for directing water flow and preventing ingress.
What Is the Difference Between Underlayment and Flashing?
Underlayment is a protective layer installed over the roof deck, typically a felt or synthetic material, that acts as a secondary barrier against moisture. It sits under the primary roofing material (like tiles or shingles) and also under the flashing in important areas. Flashing, on the other hand, is a more solid, usually metal component specifically shaped to direct water away from vulnerable joints and penetrations. Think of underlayment as the waterproof liner of a jacket, and flashing as the durable, shaped cuffs and zippers that keep water from getting into the most exposed areas.
Is It Okay If My Flashing Is Visible After the Tiles Are Installed?
Generally, no. In most standard installations, the goal is for the flashing to be completely concealed by the roofing material (tiles or shingles) or by a counterflashing. Visible flashing can be a sign of improper installation, where the roofing material hasn’t been laid over it correctly. Exposed flashing is more susceptible to damage from weather, UV rays, and physical impact, and it can also be a direct entry point for water if it’s not sealed properly. The only exception might be some decorative metalwork or very specific valley flashing designs, but for the functional flashing around penetrations and edges, it should ideally be hidden.
Verdict
So, to settle the score once and for all: yes, are flashings installed before the tile? A thousand times, yes. It’s not a suggestion; it’s a fundamental building principle for keeping water out. Trying to cut corners or get ahead by doing it the other way around is a gamble you’ll almost certainly lose, and the cost of fixing it later will dwarf any perceived savings.
My advice? If you’re doing it yourself, take your time and do it right. Watch videos, read instructions, and if you’re unsure, call a professional. If you’re hiring someone, ask them how they do it. A good contractor will have no problem explaining the process and will confirm that the flashing goes down first. Don’t be afraid to ask these questions; it’s your house, and your peace of mind depends on it.
Ultimately, a properly installed flashing system is an unsung hero. You won’t see it, but you’ll sure as heck notice when it’s not there. So, next time you’re looking at a roof project, remember the order: flashing first, then the tiles.
