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Installing the underfelt collar and transverse drainage gutter

In this five-part guide, we take you through the full installation of a Velux GGU Centre Pivot Integra Roof Window onto an interlocking tile roof using a Velux EDW Flashing Kit and a BDX Insulation Collar.
In Part 3, Mark demonstrates how to fit the frame of the window to the roof structure, refit the sash to the frame and check that everything is square and level. We then continue the installation of the Velux BDX Insulation, fitting the collar around the outside of the window frame and installing the Transverse Drainage Gutter above the window.

Take a look at the other parts here:
Part 1: Unboxing the window and preparing it for installation
Part 2: Installing the Brackets and preparing the Roof Opening
Part 4: Installing the Flashing Kit and finishing the installation
Part 5: Setting up the Bluetooth Controls

Video Transcription

Securing the window frame to the battens

So now we have the frame already inside, so we just simply lift the frame up and it’s important to take this through sideways on, so it takes up as little space as possible, so we can then safely take the whole window through the opening and then as before, rest the base of the window against the insulation. Once that’s in place, just lower the window down, making sure that you keep the cable for the mains power inside so it doesn’t get trapped. We have a little section here notched out to incorporate the cable actually sitting into the insulation. So once this drops into place, if needs be, again, just manipulate the insulation to allow the window to just sit tightly inside because after all, it’s all about having a nice sort of snug fit to the insulation. With that in, we’re now ready to start securing the window to the roof itself. So firstly, we’re going to secure the base of the window. To do that, we’ll be using the 80mm screws as well as the 30mm. The 80mm screws go into the corner. Now, it can be either of these two, depending on whether a screw or a nail head may be in the way but it’s important that they go in the corner because these screws are going to be going into the structural timber immediately below.

So this is what is securing the window to the roof itself. So with these in place, we also then just insert a 30mm screw, into the baton itself. So by inserting these smaller screws, it’s also helping to secure the insulation collar to the actual batons as well. What we now need to do is partially fix the screws into the top of the bracket themselves. So for the next step, we just take the smaller 30mm screw and we’re going to insert them into the elongated slot here. The reason for that is our next step after this is to check that everything is squared and level. So if you permanently fix and something’s not quite right, you’re going to have to remove screws. So just pop the screw into the middle of that slot, so that way we can move either side if necessary but just leave the screw sitting about 10mm proud so again, if we need to, we can pack up one side or the other to suit the level. Once we’re happy everything is squared and levelled, then we can secure it and add in the 80mm screws.

Installing the frame to check it is square and level

The importance of lifting the sash is something as simple as just getting the hand positions correct because if we get them wrong, that’s where everything becomes imbalanced or top heavy. So ideally, you should always aim to have your left hand just around that rivet point because that’s pretty much central. If you grip up here, your arm is going to be locked before you have actually got the sash completely out of the roof and if you grip down here on the longer windows, they become even more top heavy and you are in danger of dropping the window completely out of the frame. So by keeping it around that rivet point, it’s nice and secure. The right hand is key because the right hand should be going under here and the right hand is basically going to take most of the weight. But it’s also what is going to help secure the sash into the frame. So if I swing this around, so by having your right hand underneath here, you can just simply slip the barrel bolt through while still taking the weight of the window. If I lift the sash up, you’ll see a little more clearly where you just try to have the catch in between two fingers. You can also see now the polystyrene blocks which were protecting the window previously should be removed at this stage, otherwise these will actually hit off the bottom of the frame and will actually make life more difficult. So it’s handy to have a spare pair of hands just to remove these. As we come to fit the sash in a minute, the barrel bolt that we’ve just referred to is going to secure into this bushing in the right hand corner. Predominantly, it’s there for the home owner and the end user to be able to flip the window around and secure it for cleaning the outside of the window, but this is what’s going to give us that little bit of peace of mind for freeing up your right hand to guide the hinges in, as you’re just about to see. As we feed the sash through the frame, just be mindful of keeping the mains cable free of the window so you don’t get tangled up and then feed this through sideways on to take up less space. Then rotate; just make sure you keep everything upright so it’s much easier to lower the sash in and then secure that barrel bolt in. Now that’s in place, my hand is free to take the sash hinge, guide that into the frame hinge and as it’s resting there, give it a little lift and that drops in securely.

That’s not going anywhere so this side is secure and the barrel bolt is secure in this corner and I have two hands free to just push this sash out slightly, take my other free hand and just let that rest in the mouth of the hinge, then a little lift and it drops in. With the hinges now in position, we just simply undo the barrel bolt and start to allow the sash to come back around. Now, what’s going to happen is there are two small barrels on either side of the hinge here. As they enter the main frame hinge, they will meet resistance and the window comes to a rest. As you push slightly beyond that, you will hear two clicks. And those are the two small buttons that we popped in at the beginning to allow the sash to come back out and they have now popped back out and have secured the sash to the frame. We now simply close everything up and then check visibly inside as to whether everything is square and whether it’s level.

Checking the window sits level and square

To check the window is square, rather than actually trying to measure the diagonals of the opening, the easiest way with the sash in place is to just check the gap that runs from the opening sash to the fixed frame. If everything is square, you’ll find that the gap as you can see in this instance, is even all the way down. And it doesn’t matter which side you check. Either/or will tell you whether the frame is square to the sash. If it isn’t, you would find the gap either at the top or the bottom is tighter. Whichever is the tight corner, whether it would be top right or bottom left, if you like, you would have to lever the frame along a little just to even up that space. And once the gap is even then you can go on to check the level. So that is another advantage of having that 20-30mm tolerance on either side. Once you’re happy everything is square, we then open the sash up just enough until you can see a little bit of daylight through the bottom of the sash. And again, rather than trying to put a spirit level across the base, if this gap is even from end to end, we know everything is level. If you had a gap that was higher on one end, so if I just push this section up a little now, you can now see how we have closed the gap off here and it’s much larger here.

So whichever would be the tighter corner, you would push that corner up and then you would secure it using the spacer that we provide, the little packer which has 1mm, 2mm or 3mm thickness. So pop that under the corner bracket until we get everything level. Once we’re happy it’s all square and level, we are then ready to remove this sash again to give us all of this space to work through to fit the under felt collar and the flashings. So the method used to remove the sash is basically the installation but in reverse. So open the sash up and we’re going to use the barrel bolt here, again, to secure the sash into the corner. We then have to pop the little buttons in as we did at the beginning, and we’re now ready to bring the sash back towards us and keeping it upright, this will enable us to just slide the sash out from the frame as I’m about to demonstrate. With the buttons popped in, we then release the barrel bolt and start to let the sash come back towards us.

It’s important that we get the angle correct before we try to remove. If we allow the window to come too far back, it becomes top heavy and again, harder to hang onto. If we tried at this angle, the hinges have come further into the frame hinge and will actually provide more resistance. So by keeping it upright, we can pop our hands in the same positions that we had to install and then you can just walk the window forwards. Then as before, turn it sideways and just gradually just bring the sash inside the room and then store it for inserting later.

Preparing the roof opening for the transverse drainage gutter

With the sash removed, we now have all of this space to allow us to carry on working from inside. So I can now pop my head out through the frame and secure the rest of the top brackets with our longer 80mm screws. So with our two remaining 80mm screws, we’ll pop those into the corner as we did at the base. So once that’s secured in, fix the smaller screws as you go, and what we then have is a fully secured window, completely tied into the roof structure. One of the main features of the under felt collar is the fact that we have a drainage channel included which situates above the window and the whole purpose of that is to catch any water that may run down the membrane through a broken slate or a broken tile, thereby stopping it from getting into the roof structure itself.

So for this gutter to be effective, we need to cut a small flap in the existing membrane which will then tuck into the gutter itself. So if you had counter batons running along the roof, at this stage you would need to remove a section of the counter baton to ensure the gutter rested directly on the membrane. But for most standard roofs, it will simply be a case of take the gutter, rest that onto the membrane and treat it as you would any other form of gutter. So you want a slight fall on the gutter itself. Then using the base as a straight edge, just cut along the bottom between the rafters. Move the gutter away and then just extend the cut into the middle of the rafter itself and then do a small return on either side.

Now you can see once the installation is complete, this is basically going to pop inside here along with the rest of the felt collar. By doing this, we have created a weakness in the sense that water now may be able to penetrate underneath here, which is why included as part of the kit, you have these two strips of butyl putty. And what we’re going to do with the butile is peel off a strip for each side and stick that to the felt. Just use the whole length. There is no harm in being generous. And just run that down the outside edge into the membrane, and do the same on the opposite side. Once we secure the gutter to the roof with the screws that are provided, with this peeled back, this is going to seal to the underside of the gutter and therefore, create a little waterproof barrier so nothing can penetrate through the side and in through the cut that we’ve made in the felt itself.

Installing the underfelt collar

The under felt collar is the next part that we’re going to fit now. So you’ll see when we start to open this up, it’s basically just a breathable membrane that can be attached around the window to enable the roof still to breathe and allow moisture to evaporate but also to ensure that water can’t penetrate through and into the roof structure.
So you see as we open this up, there are pleated sections which will become more apparent as we fit it around but it’s to give you flexibility for going up and over the batons. As we completely open this up, you’ll see there are two different sizes of the flat membrane. There is quite a large section here and as we bring the rest of it up towards you, you’ll see a shorter section at this stage. This shorter section is the part that’s going to go at the base of the window. So we take the larger section initially and feed it up to the top of the window and then initially just hook that in place. The weld seems here to actually help the felt collar to sit quite snugly to the frame before we actually attach it using this butyl putty. And that’s the next stage to secure this to the window itself. Here, we just push the felt down until it’s level to the top of the window and then we’re going to peel back this protective cover, similar as to what we did earlier at the top of the window, and once we’ve peeled this back, we’re going to stick this so it’s level to the top of the frame.
So to begin with, we start at the corner, peel back this cover and then initially just fold this section around so it can just stick to the side of the window. Then as we just carry on peeling and sticking this to the window frame itself, so the benefit of this means it doesn’t matter what type of window you have, whether it’s pine, white painted, polyurethane; this will stick to all variations. When you get to the end, we then just fold this section around and then attach that as well. Whilst we’re at the bottom, because we have to have this in close contact with the membrane, we need to just slip this underneath the baton…

So now anything that were to run off here will be able to carry on down the roof structure. Obviously, now we’re just going to secure the baton as we would have prior to fitting the felt collar. So with the side, it’s important not to try and make this flush to the top as we did at the bottom. It’s just about continuing that height profile. So with your hand, you’re going to push into the corner section where the window comes into the roof and keep it at a nice, tight 90 degree section. So as we did at the bottom, peel the corner away; initially just apply that to the corner and then as we work our way up, just stick this to the frame as we go. And then when we get to the top, that section will wrap around it as it did at the base. The next part of the installation is to try and get the membrane to sit as close as we can to the existing roofing membrane. That’s why we have all of these pleats here. So as you bridge a baton, we just break the pleats away and that enables the membrane to dress neatly around the baton. And then to secure it, we can just hold that in place with a staple. And then we just carry that on as we work our way up. Each time we meet the baton, break the pleats and staple in.

Installing the transverse drainage gutter

Having secured both sides and then secured the adhesive around the top of the window itself, it’s now time to secure the drainage channel to the roof. The drainage channel is extendable so it can extend either way to suit your preference and you will see as you extend, you are left with the option of a single hole on one side and multiples on the other. You will generally find it easier to start with a single hole at the high end because that’s going to be the first point you want to fix into the roof. So at this stage, just lay the gutter against the baton because we need to fold our membrane over, lift up the existing cut that we made in the felt earlier and we just need to now slide the drainage channel up until it makes contact with our cut. That’s our fixed position. So we now know this is where we have to fix the gutter. To do so, you have the remainder of the kit that was supplied where we have a bag of screws contained within. So open the bag up, and we’ll just need two of these screws to do the job.

So just double checking our position again. We’ll pop that screw in. So this screw has now driven into the butyl underneath, as you can see, and created that little seal to stop any water creeping underneath. So we just repeat the process on this side. So fold the membrane up, extend that back until one of these holes lines up with the structure beneath, get it into the correct position and secure the screw. Now just simply fold the membrane over, take the section that we cut earlier and just with your fingers, we just want to push this into the gulley and you’re basically creating a membrane gutter section. To secure that in place, we’re going to use the clips that are provided. So these clips are wedge shaped so the thin edge of the wedge will pop into the gutter, therefore allowing any water that comes inside to still run through. So the easiest way I’ve found to secure these into the gutter is just to pop your fingers inside, slide that into the gutter and then put your thumb underneath so you can anchor it and then just pull that down. And that clips into place. Keep going along and doing the same with the other clips. And depending on the size of the window, you may only need three; you may need to use all six. A lot will depend on whether you’re going to be able to put the flashings over the top of this tonight. If you want peace of mind, pop all six in in case the wind gets up over night and therefore, you know nothing’s suddenly going to come loose again.

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