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How to Install a Velux Top Hung Roof Window on a Profile Tile Roof - Part 2

Installing the BDX Insulation Collar and the window frame

Top Hung Part 2:

In this 4 part guide, Mark - A Velux Technician takes you through the full installation of a Velux GGU Centre Pivot Roof Window with a White Polyurethane finish. This window is being installed onto a plain tile roof so we’re installing an EDP Flashing Kit and BDX Insulation Collar.

In Part 2, we demonstrate how to install the Velux BDX Insulation Collar and how to fit the frame to the roof structure before checking that the sash sits square and level in the frame.

View the other parts here:

Part 1: Unboxing and preparing the window for installation
Part 3: Underfelt collar and Transverse Drainage Gutter Installation
Part 4: Installing the EDW Flashing Kit and Finishing Installation

Video Transcription

Measurements and Tolerance

So prior to installing the window and the insulation products, we've prepared our window opening as per the installation instructions. You can see here, as it's a standard red line installation, we've allowed on the width an extra 40-60mm over and above the width of the window. We have a 780mm window so our frame opening here should be anything from 820-840. Installation battens are then positioned, ideally always from a full row of tiles below the window. Try to avoid cut tiles because they are very awkward to weather incorrectly and you're always leaving yourself open to water ingress. So our first installation baton should always be 80mm from the top of the tile to the top face of our first batten. Slide the tile across and just double check that everything is as we would hope and should be nice and level. We then want to make the height of the opening the height of the window plus an additional 45mm.

So with our window being 980mm, our opening should be 1025mm. This tolerance that we have factored in allows for adequate insulation. It also allows for expansion of the roof on a warmer day but also gives you invaluable wiggle room so you can square up the window if things aren't quite as you had hoped when you first fit the window into the opening.

Assembling the BDX Insulation Collar

So the next stage of the installation is for us to form the insulated frame ready for the window to sit inside. So the idea of having that tolerance around the window as we mentioned earlier, is to make sure we can adequately insulate around it. Here, we have a purpose made product that was quick and easy to insulate. You’ll see the code on the first line here, 'BDX', just refers to the fact that what you have inside the box is an insulation and an under felt collar which we'll come more to as we go through the installation itself. The second line again refers to the window size this is designed to fit. So again, you want to make sure that this code matches the code on your window carton, otherwise it won't fit. As before, we show weights, etc, and also we have our no knife symbol because on this design of box, we have two small tabs located about three quarters of the way down the box, just by this symbol, advising how you're actually going to open the box up.

So you just pop the first tab up, grab hold and just pull that towards the top. Take the next tab, pop that up and then just pull that towards the bottom. Then just simply peel that section apart, same at the top and then open this little side piece up so you can get clear and easy access to the contents of the box. As you can see, we have a set of installation instructions contained inside here that are specific to the next following steps to install the insulation collar and the under felt collar, but I’m going to take you through those steps just now. With the box open, it's only these sections here that we initially require. These are the parts that make up the insulation collar. Everything else inside the box, we'll come back to later on because this is our under felt collar drainage channel, etc. So this box can now go safely to one side for future reference. Here, we have the four parts that make up our insulation collar. The two longer sections here will go on either side of the window with the two short sections for the top and bottom.

When we look at the side sections, you'll see an additional layer of slightly more soft foam than on the inside. This is to give you a little bit of play, depending on whether you have allowed 20mm or 30mm tolerance on either side. If you've gone for the full 30mm, we retain all of the insulation. If you've only left 20mm, this soft foam layer here can be peeled off. If you've only left 25mm or so, the foam is soft enough that it will compress once you actually fit that into the opening. To fit the top and bottom sections, you peel back the corner of the soft foam to reveal the bracket into which the opposite bracket from the top section is actually going to engage into. So as we can see on this top section here, we have a little L-shaped return on this bracket which is going to slot into this channel. So as I bring this around and start to run that through, you can see how the foam is actually cut to shape so you know you've got these the right way around. As we push this down in, this square section here is going to pop out through that small little window and that will be the parts locked together. Pop the soft foam back and then we're ready to put the second side on. The same concept as before, we just flip this around, keeping this ledge on the outside edge because this is what's going to rest on your batons. Peel that back, drop that little bracket in there and clip that together. And then for the final section, we just need to take the whole lot, flip it around and then just clip the bottom section in as we go. Now it's fully assembled, we're ready to take it inside and carry out the rest of the installation process from within the roof.

Placing the Collar and Frame in the roof opening, ready for fixing

Taking the insulation collar, we feed it up through the opening in the roof, resting it against the bottom installation batons so again, it doesn't slide off the roof and then gently lower it back towards you. The insulation is tapered at the top so it is designed to be a snug fit so you just need to ease the insulation past your top installation baton and everything should sit nice and snugly. And we're now ready for the window frame to sit inside this rebate

Take the window and do exactly as we just have with our insulation collar. Feed everything out through the roof, lower the bottom section in first. So again, it's got a nice, solid anchor and then lower the window towards you. As we get towards the top, it should meet a little bit of resistance so you just have to move the insulation away from the window until everything falls into place, like so. Don't be tempted to pull down on the window, because at the top, we have this insulation and there is a danger you're just going to break this off. So everything should just be easy insulation away rather than force the window in. Now with this in place, we're ready to start fixing the window in.

Securing the frame to the roof opening

So for fixing our lower installation brackets, we're going to use one of each screw: the longer and the shorter screw. The key fixing point is positioning the 80mm screw into our corner fixing point here, because just below here is the roof structure. If you couldn’t get a fixing into here because possibly the nail head for the baton is in the way, go for the nearest one to it. As long as you're fixing into the structure, that's key. With the 80mm in position, we then take the 30mm and just secure that into one of these other fixing holes across the middle and these smaller ones are also now helping to join the insulation collar to the window itself. Take another pair of screws and just repeat the process on the opposite corner. Into the furthest away hole, and another one into the middle. So with the base secured, we now go to the top brackets but only partially install the screws up here which you'll see just next. Now, at the top of the window, we only want to partially secure the brackets because our next stage is going to be to check the frame is square and level. So we need to give ourselves a little bit of movement.

So at this stage, we're only going to be popping the 30mm screw into this elongated slot on each bracket and it's also important not just to aim for the middle of this slot but to leave the screw sitting approximately 10mm proud in case we have to elevate a corner. And the same on the other side. So with those partially secured, it's now time to install the sash and check visually if everything is square and level

Best practice for handling the window

The key thing to know about installing the sash is to have an understanding of the hand position to get the correct technique. Otherwise, it can become a very complicated process. So the one thing that will work in your favour and give you that little bit of security is the barrel bolt that's located on the sash. Primarily used for allowing the home owner to secure the window to clean the outer pane but also for the installer, something that allows you to lock the window in during installation. As this is a top hung window, there is actually a barrel bolt on either side. So if you're left or right handed, you can take your preference. But whatever hand is your strongest is the one that you're going to have underneath, taking the weight of the window. As I’m right handed, I’m naturally now going to position my left hand around about the central point of the window. This hand doesn't take a lot of weight, but getting the hand position right is key for balance. If we grip to high, your arm will be locked before the sash is fully extended out of the roof and if we grip too low, the window becomes top heavy. So keeping it central gives it a good balance.

On this side, I’m going to slide my hand underneath until I can feel that barrel bolt. So as that's extended, you'll be able to incorporate that into the bushing and secure this corner. So strong hand underneath; left hand will be for balance. And then as you lift, the one thing you will need is ideally a spare pair of hands to be able to remove these polystyrene packaging, otherwise they can actually hit off the bottom of the frame and again, slightly complicate the installation. One thing to bear in mind before we insert the sash is the importance of protecting the base of the frame. After all, this is pine which is a soft wood, so whether it's white painted or the varnished pine version of our windows, what you don't really want to do is rest the sash quite heavily on the bottom of this frame during installation.

There is a chance you're going to dent or possibly even scratch the internal finish. So either find a little cover, whether it's a jumper, a jacket, even a thin piece of card so that you don't accidentally catch this but be aware of the fact that if accidents happen, you can buy a touch-up kit which will cover up any scratches, repairs or dents and you will be able to buy the VELUX touch-up kit through JJ Roofing Supplies

Attaching the window to the frame

So bring the sash through sideways on so we take up less space and we're less likely to catch the window itself. Bring the whole window outside and then lower it down upright to avoid impact again, until we lock that bolt in. Now the bolt is locked in, I have a free hand which will allow me to guide the first hinge into place. So using my free hand, I’ll just rest it against the mouth of the hinge, a little lift and that drops into place. I now have two free hands so I can come over to this side, push the window out slightly, line the hinge up with my spare hand, a little lift again and it's in. We now undo the barrel bolt and as the window comes back around, we have two little barrels on either side.

Once they make contact with the hinge, there will be a point of resistance and as we go past this point, you'll hear two clicks which are the buttons we popped in at the beginning now popping back out to secure the sash to the frame. And everything is now secure, ready to check that it's square and level.

Checking the roof window is square and level

So now to check whether the sash and the frame are square to each other, we simply pick a side. It can be either side; it doesn't really matter. And you're just looking at the gap between the sash and the frame and you're just checking that that gap from top to bottom remains equidistant. If it were tighter at the top here, we would simply move the frame along a little bit, either by hand or possibly using a small crowbar behind the insulation at the opposite corner to just bring it along. Once that gap is even, it's square. Then to check it's level, we open up the sash and look across the bottom.

So to check whether the frame and the sash are square to each other, we follow this gap between the sash and the frame and you want the gap at the top to be the same as the gap at the bottom. If it is, it's square. If the gap were a little tighter at the top than it is at the bottom, it would be telling us the frame would need to move this way to open the gap. So you may be able to do it just by pushing with your hand or a small crowbar on the opposite corner but behind the insulation would allow you to jimmy that along. So for the level, we follow the same principle as we did for the square, but this time, we open up the sash until we can just see a little gap of daylight. And again, we're just looking to make sure that the gap on the left is equal to the gap on the right. If the gaps are different, so if I were to push this corner up where you could then see where we have less gap here than we do here, it shows it's not level and whichever is the tighter corner, you would need to push up and then use the packing piece that we provide with the brackets to help level that off.

Once you're happy it's level then we're ready to take the sash out and secure the window to the roof.

Removing the sash and fully securing the frame

Now, the removal of the sash is basically the same as the installation principle but in reverse. So we're going to take the sash out to give us all of this space to work through, to secure the upper brackets and carry out the rest of the installation. So rotate the sash and as we did previously, secure with the barrel bolt. Pop the two buttons in and then before we remove, you want to make sure you have the angle right. If we try to take it out at this angle, leaning back to us, the hinges are going to meet resistance with each other and it's going to become very difficult to remove. If we over-rotate, it becomes top heavy and we're in danger of dropping it. By keeping it upright, it will be a lot more straightforward to remove. But also bear in mind, because this is a top hung window, these arms are going to move slightly as you try to release the window so it may not come out as smoothly as a centre pivot window. So it may require a couple of extra pushes here and there, gently of course. Once out, rotate the sash around and then carefully bring that back through the frame and then rest it on a piece of card somewhere to keep the top clean as we said before.

So the final part of the installation here is now to secure the top brackets using the remaining 80mm screws and to tighten the 30mm. So as before, position the 80mm screw in towards the corner. Once that's secure, tighten up the 30mm. And move over to the other side and repeat.

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