Hi, I’m Matt Woodyatt, the Training Manager for Redland and I’m here today at JJ Roofing Supplies Trading Centre at Cricklewood.
We’re looking at valley detail today. We’re really spoilt for choice when looking at ways to fill in a valley. We have got our traditional lead. We have got GRP open valleys now, dry valley and also what we’re looking at today is lead replacement, Rapid Flashing.
Today we’ll be installing Wakaflex Rapid Flashing on a 100mm open valley. So we’re going to have tiles overhanging either side, 50mm to give us a 100mm space in the centre where we will dress this butyl rubber material in as a lead replacement.

Rapid Flashing is made of butyl rubber with a wire mesh through the centre to give it strength as well as flexibility. We have perforated sheets on the back so you can take the back cover off in pieces to lay with ease of application and as you will see, on either side underneath we have a butyl strip to adhere to the roof material while you’re putting it in place.
We’re going to be installing Wakaflex Rapid Flashing into this open valley here. We’ve got the boards already in place, tile battens in place and also a batten here to welt up the edges of the valley detail to prevent the water from spilling out over the top. We’ll protect this further by welting up the material itself on the edges, as you will see shortly. Rapid Flashing, Wakaflex Rapid Flashing can be laid in lengths of 2.5m as opposed to with lead which is 1.5m. So we are using fewer laps and less wastage on the roof.

The first thing we do is lay the Wakaflex Rapid Flashing into a valley detail. It’s a nice, light material so compared with lead, easier to handle, easier to move on the roof. We can measure it in detail, bring it down to the bottom of the valley and mark where we want it to be trimmed off at the bottom to feed into our gutters. We can cut it with a simple pair of scissors or a pair of snips like I have here. It’s easy to cut but difficult to tear.

We have the Rapid Flashing piece places into the valley detail here, positioned over the boards, levelled off with the bottom which we can trim to the shape of our gutters later on. What we need to be doing now is tacking the material into the battens beneath and then forming the material into the boards of the valley so we’ve got a nice, slick surface for the water to be carried down the roof.

So we have our material in place now, over the board and over the battens to the left and right. We can trim that off later to suit the gutters beneath but for now, we’re going to keep it in place and tack it into the battens that are preinstalled either side and start to form the material into the valley. It’s got that stretchability controlled by the wire mesh inside which will allow it to move and form to the shape of the valley beneath. At this point, we can remove the backing strip on one side, then the other to allow us to tack the material into place over the battens beneath, like so.

This means we can work with the material with the sides sticking down while we’re doing that. We don’t want the butyl to stick to the batten as we’ll be curling that back up in a moment and welting it upwards. Popped on a glove now, and just starting to play with hammer and nails. We’ve got our first fixing into the top of the batten here.
We just want enough fixings now to hold the material in place at the side of the batten.
And then when we’re ready, we can remove the seal from this side and tack it in exactly the same way. Remember to remove the central piece as well. You don’t want to leave that in place because you want the tackiness beneath the material to help it stick to the roof detail.
So we’re just tacking the material in place as we move up, again, making sure the butyl strip doesn’t stick down the underlay beneath so we can welt that up shortly and we’ll have another series of tacks holding those in place.

So remember as we’re tacking the material down initially, we want to leave enough overlay here so we can welt the material back. We’re then going to place another series of tacks up either side of the valley detail to hold that welt in place and then the tiles will then sit over the top.
You might want to take your gloves off to do the welt, as you will lose them as they stick to the butyl.

Don’t worry about it looking pretty. It’s there for a function, to carry water back into the valley and at the end of the day, the tiles will be overhanging this by 50mm so you’re not going to see the detail. Rapid Flashing material, if there is any slack on the sides, should fold in quite neatly into the valley as it stretches in either side. If you want to use a roller to support you doing that then feel free, but at the end of the day, all you want is a nice, smooth run of the material down your valley, resting either side.
We’ve now completed the installation of our Wakaflex Rapid Flashing material and our lead replacement material. We’ve got a single piece. We can have pieces up to 2.5m so for a small valley such as this, you don’t need to have 150 laps wasted material where the material is overlapping each other. Remember with lead, you can only have a piece of 1.5m before you need a second piece cut and a 150 lap, whereas with Rapid Flashing Wakaflex, you’ve only got one lap after 2.5m.

We’ve got the system installed here, the Rapid Flashing Wakaflex in place, stretched into the detail, tacked in along the battens either side. We’ve got that backing seal removed to allow the material to tack to the valley boards beneath and then welted up either sides, the butyl is actually facing upwards and tacked in up either side of the valley.
What we’ll be doing now is actually putting the tiles either side of the valley with a 150 overhang to finish the detail off. As we’ve mentioned, you don’t need to have a lap with a small valley such as this but where you do, Rapid Flashing really comes into its own. You don’t need any tapes or glues with Wakaflex Rapid Flashing. It sticks to itself. In fact, it chemically bonds to itself. If you put two pieces of material together, they actually become a single piece so where after 2.5m we do have a 150 lap, you simply put two pieces over each other and securely wedge them together. You’ll find once that material has been put together, after a few moments of it being placed there, it actually chemically bonds and you are physically destroying the material to get it apart. It actually becomes one piece so there is no need for clips or glues when you are sealing laps with the Wakaflex Rapid Flashing.
So the detail is almost complete now. We have got the lead replacement material in the valley, tacks on either side and welted up on the sides. We’ve now cut the tiles following the line of the valley up and down the roof. They are overhanging into the valley by 50mm which should when complete give adequate space for the rain to flow into there and allow liquids to flow down the roof and into the guttering beneath.

Remembering the BS5534, each of these perimeter tiles, each of these are a perimeter tile either side of the valley, needs to be fixed twice. So two mechanical fixings per tile either side of the valley. If you have lost the nail hole, as we have on the top tile up there, you’re using clips such as C-clips, Kro-clips or tile clips which we’ll look at elsewhere.
So we’ve completed the valley detail now. We’ve got the material in place, the lead replacement material in place on the valley board, tacked in either side and welted up to really weatherproof that valley detail. We have done half the tiling now, tiled in, 50mm overhang into the valley which when we mirror that, the other side will give us a nice 100mm gap in the centre for a 100mm open valley allowing liquids to flow down the roof and into the guttering beneath.

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