What Exactly is a Roof Valley, and Why Should You Care?
A roof valley is the ‘V’ shaped channel where two sloping roof sections meet. Think of it as the main artery for rainwater on your roof. It funnels a huge volume of water down into your gutters. When it’s built correctly, it works perfectly for decades. When it’s done wrong, or as it gets old, it’s one of the most common places for a serious leak to start. I spend a lot of my time in Brighton and Hove fixing valleys that other roofers have botched or that have simply failed with age.
What Are the Different Types of Roof Valley?
There are a few ways to construct a valley, but they generally fall into two categories. What you have often depends on the age of your property and the original builder’s preference.
Open Valleys
This is my preferred method for a long-lasting repair. An open valley has a visible metal or GRP (fibreglass) channel running down the ‘V’. The tiles or slates are cut and angled back from the centre line, leaving this channel exposed. The most common materials are:
- Lead: The traditional choice. It’s durable, flexible, and when installed correctly, can last over 50 years. It’s a specialist job, and my experience in expert lead work ensures it’s done right.
- GRP (Glass Reinforced Plastic): A modern alternative. These come as pre-formed troughs. They are very tough, smooth (so debris washes away easily), and quicker to install. A very reliable option.
- Zinc/Copper: Less common in residential properties around Worthing and Sussex, but still excellent, long-lasting materials.
Closed Valleys
With a closed valley, you don’t see a metal channel. The tiles or slates are laid to cover the valley entirely. A ‘woven’ valley has the slates interlaced across the join, which looks beautiful but is very difficult to get right. A ‘cut’ valley has one side of tiles running underneath, while the other side is cut neatly over the top. While they can look tidy, they are more prone to getting blocked with moss and leaves, which can cause water to back up and get under the tiles.
What Are the Most Common Roof Valley Problems I See?
When I get a call about a leak, the valley is one of the first places I check. Here are the usual suspects:
- Cracked Mortar: On older properties, the tiles in the valley were often bedded in sand and cement. Over the years, this mortar cracks and falls out, leaving gaps for water to pour in. This is a very common failure.
- Debris Blockages: Leaves, moss, and twigs build up in the valley, especially if it’s a closed one. This creates a dam, and rainwater has nowhere to go but sideways, under your tiles. Keeping your roof and having clear gutters and downpipes is essential to prevent this.
- Botched DIY Repairs: I see it all the time. Valleys covered in layers of bitumen paint, flashband, and mystery silicone sealants. These ‘repairs’ almost never work for more than a few weeks and just trap moisture, making the underlying problem worse.
- Poor Installation: Tiles cut too short, not enough underlay beneath the valley liner, or the wrong fixings used. This is just poor workmanship and is guaranteed to fail prematurely.
Can I Repair My Own Leaking Roof Valley?
My honest, blunt answer? No. A valley is a complex and critical part of your roof structure. Getting it wrong doesn’t just mean the leak continues; it can lead to serious rot in your roof timbers.
If you’re in an emergency and water is coming in, you could get on a ladder (safely!) and apply a bridging product like Acropol or a roofing-grade silicone directly to a visible crack. BUT, you must understand this is a temporary, emergency patch. It’s a plaster on a wound that needs stitches. It will not last.
If you see any of the problems I’ve described, don’t waste your money on temporary fixes. The only permanent solution is to have the valley stripped back and rebuilt properly. If water is actively getting in, you need my urgent roof leak repair service to get it sorted quickly and professionally.
The Right Way to Build a Roof Valley
When you hire me to fix your roof valley, I don’t patch it. I replace it. Here’s how I do it properly:
- I strip back the tiles or slates on both sides of the valley to expose the timber structure.
- I remove the old, failed valley liner and underlay.
- I install a new, high-performance breathable underlay, ensuring generous overlaps for complete protection.
- I fit new treated timber battens.
- I install your choice of new valley – either a pre-formed GRP valley or a custom-made lead valley.
- I then re-lay the tiles or slates, cutting them precisely to create the perfect channel for water flow and securing them with the correct clips and nails.
It’s a methodical process that requires experience. When I’m finished, you have a valley that’s built to last for decades, not just until the next storm. It’s a core part of any proper pitched roof replacement and repair project.
If you’re worried about the state of your roof valleys, don’t guess. I can give you a clear, honest assessment. I provide fixed-price quotes and you can even track the job’s progress through my client portal with daily photo updates. The first step is easy – book a free, no-obligation roof inspection and I’ll tell you exactly what’s going on up there.