hello again in this set of short videos I will be showing you how to create a fiberglass roof from start to finish you can use the example shown here in the video and the back up on the website to complete your very own fiberglass roof project this video is part 1 and it covers basic roof decking and preparation for fiberglass roof trims here I've made a quick flat roof mock-up in Photoshop so that we can quickly run through some of the basics this is a fairly standard construction the sort that's found on many flat roofs throughout the UK this is the roof decking and it's clad with 18 millimeter OSB three timber and if I just x-ray the deck with the powers of Photoshop for a moment you can see the roof rafters underneath that the roof deck is fixed too there are three types of timber you could use for a fiberglass roof WBP plywood 8 by 4 OS b3 or 8 by 2 OS b tunnel and groove let's just have a quick look at these options first there let's talk about plywood and if you're considering using ply it has to be thoroughly sanded down first with 40 to 60 grade grits paper this is to create a rough surface for the fiberglass to a deer to and stop it delaminating at a later stage so unless you have some nice clean WBP ply lying around and lots of spare time to sand it personally I wouldn't bother here are really your two best choices and they're both OS b3 this is because OS b3 is designed to resist moisture and as a nice rough surface for fiberglass to grip onto so as long as you keep it clean and dry you will be okay let's look at probably your best option if you can source um and that's the 8 by 2 tongue and groove OS b3 the boards are laid in a brick bond fashion as seen here typically running at a 90 degree angle to the roof joists underneath and because the boards are tongue and groove this means that every edge of the board what's itself upon the other they also have a host of other benefits and amongst these things is that there will be easier to carry and will produce less waste in cutting so unless it's a small job I really would try to get hold of these after fixing the first board writing side up simply tap the subsequent boards firmly together with the writing and gap side up also and fix them into position just make sure you leave a 25 millimeter expansion gap wherever the roof deck meets and abutting wall like this your second best option is the 8 bar for OS b3 roof deck constructed for no surprise 8 bar for OS b3 otherwise known as 2.4 meters by 1.2 meters for the longer to say metric measurement purposes and this is how the exact same roof would look constructed from 8 bar fours again if I x-ray the roof decking for a moment you can see how this may work out on the rafters underneath but this time because we're using non tongue-and-groove 8 bar fours we have to allow an expansion gap of 3 millimeters between the face of each board before fixing like this and this would also be true if you were using plywood instead again the writing side should be facing upwards and a 25 millimeter gap near any abutting walls and because you're not using a tongue and groove profile you will need to tape and bandage all board joints and I'll show you how to do this a little later on and yet again this is also true of plywood if you're using it anyway enough of Photoshop let's have a quick look at a small roof mock-up that I've constructed at floor level and I'm going to show you in photos and video every stage through until final completion I've constructed the roof deck using standard square edge OS b3 rather than the tongue and groove profile and that's just because it's a very small roof and I can show you how to tape and bandage any boat edge joint should you have one if you're using 8 by fours if we just swing the camera around for a second you can see that have allowed a 25 millimeter or one each gap between the roof decking and the pretend up stand ward at the rear now back at the front this is the lowest part of the roof and here I have fixed a drip button to the front face of the fascia and its purpose is to position the fiberglass drip trim that we'll be using later into the guttering here is the drip button viewed from the side and if I superimpose the drip trim into place for a moment you can see how this might work the drip batten size can then be adjusted to get the correct amount of extension into the guttering below if the curve in the drip trim on the outside edge makes a small gap you can place some dots of PU adhesive or fix all if you like that will pack it out and stop trim rattle in windy conditions alternatively if you're using a larger drop profile drip trim you can lower the position of the drip button and use pure adhesive or fix oil again or on a very large drip trim you can use two buttons to fit the drip trim to if in doubt put a smaller section off and hold it in place on the roof to see how it fits this is the drip trim I'll be using in this demonstration and it's the a1 70 and it has roughly a 65 millimeter drop on the front face which as you can see sits nicely into the guttering if you did want to sit the drip trim flush against the front of the drip button you can also plane or route the top edge of the drip button to the same curve as the drip trim the next button trim we require is once and support the rear of our raised edge trims on this side of the roof I have sat the batten trim flush with the roof so let's see how this one works here we are looking at the side fascia and the button trim this is the B 238 raised edge trim it's the smallest raised edge trim with a solid profile of roughly 105 millimeters and this is how our plan for the trim to sit on the roof deck and against the button trend again PU adhesive can be dubbed onto the battle trim to stop trim rattle if you require it on the opposite side of the roof I'm using a slightly larger raised edge trim so I've decided to lower the trim button slightly from flush with the roof deck to just below of course I didn't really need to change trims all button positioning but it shows you can move the trim buttons up and down to help support the trim if you think it's necessary or indeed double them up again a few dabs of pu adhesive here will stop trim rattle in windy conditions especially with larger trims the larger trim you go the more potential rattle you could get here I will be using the b-26 deep raised edge trim for no other reason than it will show it being used so you can see what it looks like on the roof when it's done it has an approximate 125 millimeter front face and this is how I have planned for the trim to fit in this situation so finally you can see how the roof decking and battens are now completed and ready for the trims to be cut and fitted but there is just one more final option before you pack away your woodworking kit and that's the possibility of rebaiting your front drip trim if we just imagine for a second that the front drip trim is on the roof deck and then if we swing the camera around to look at the top flange of the drip trim you will see that it's proud of the roof surface by about two millimeters and by the time we apply bandage in the next video this could be as much as three millimeters this means that if your roof is totally flat and doesn't have the appropriate fall it may hold a little water if this is the case and you want to address the problem this is how you do it simply hold a length of trim on the roof in position next draw a line across the rear of the trim make sure any screws or nails are screwed or punched below the depth of three millimeters and then rout out to a three millimeter depth now you will have a nice flush fitting drip trim having said all that I hardly ever bother as the fall is normally sufficient and the ponding is usually minimal also a fiberglass roof is totally waterproof and jointless so it certainly won't affect the performance in any way but if you need to it is an option and it's relatively easy to do if you need information of available trims and trim sizes as well as applications these are all available on my websites in the links provided and in the description bar well that concludes this video on roof deck preparation and in the next video we'll be cutting and fixing the roof trims see you there you