* Free DIY tips *- Polycarbonate to brick wall transition
So spring is on the horizon and those of you with (or thinking of) a polycarbonate conservatory/ lean-to roof will find this of interest.
KRS recent project was to fix a leaking wall flashing where a conservatory gasket flashing kit has failed.
There’s nothing wrong with the original installation it’s just old and worn. The rubber strip pinched down on to the polycarbonate sheet had become brittle and wind blown rain was penetrating through it.
Here’s how we remedied it using DIY products found locally. Remember to cover your polycarbonate with a dust sheet and always work from duck boards spanning the area you need to kneel on. Edge protection and a fall arrest system is a must for health and safety!
Step 1 – Inspect the lead cover flashing for any defects like cracking. Ensure the lead flashing lengths are in accordance with LCA (Lead Contractors Association) installation musts! They should be no longer than 1.5m long and overlap minimum 100mm. On this project I noticed that this was all fine except I replaced the old silicone with mortar as silicone is only guaranteed for 5 years generally and also I clipped each flashing to prevent wind uplift. See pictures
Step 2 – Clean the polycarbonate free from debris, dust or any silicones along your flashing line. You are now ready to brush on your adhesive primer for your flash band. Ensure the primer covers all areas you need to install your new flashing and that you check the drying time for your product. It is important to note that most DIY printers and flashing kits require the working area to be completely dry! See pictures
Step 3 – Cut to size your flash band sizes (using a sharp knife on a sacrificial piece of timber so as not to damage the surface below) ensuring side and end laps adhered up the up stand. Where an angle occurs it’s best to use a Single Ply Membrane detail where you envelope the flashing vertically.
Please note that when using a flashband product the substrate adhering to must be as smooth as possible because remember you are only using a product that’s a few mm thick. Also this product can be very sticky when warmed up by the sun so try to keep it in its white wrapping and in the shade when not using to avoid getting in a tangle.
Take your time!!!! Install flash and product methodically.
Step 4 – Glazing bar end caps are installed similar to that of a standing seam metal roof. This ensures that everything around this detail is overlapped the correct way right up under the cover flashing. Again take your time with these and probably best using scissors for these small flashings and save your fingers from possible mishaps!
Step 5 – install your lead clips with fixing points up the up stand. General flat roofing code always require a minimum of 150mm up stand with no penetrations however sometimes this is just never achieved. An example I always used to come across of this is a roofing product up stand under a door threshold where people walk out on to balcony or terrace. The threshold is always as low as possible to avoid a big step and thus the flashing can never achieve its 150mm height.
Step 6 – Tap your lead cover flashing back over your flash band adhered flashing with a lead beater preferably. If you don’t have one then I’d use a piece of timber batten with a hammer. Again take your time with this. Lead in all its thicknesses is mailable and forms angles nicely.
Step 7 – Rake our your old mastic and replace with a nice 3 & 1 mix of either builders sand or sharp sand and cement. Use a waterproofing plasticiser added to the mix for peace of mind. A small pointing trowel is needed to push the mortar all the way in your raked out joint. Smooth over and let dry then brush off with a soft brush.
Step 8 – Lastly finish off any mastic that is needed. You may have cut the mastic by the glazing bar along the flashing line to stick your flashband so this needs touching in. Also I like to silicone the lead flashing ends to be sure. A termination bar can be fixed to your flash band here as is a standard Single Ply Membrane detail.
So you’ve now installed your watertight transition from your polycarbonate roof to your wall!
Here’s a list of what you need for a 4m flashing :-
1- 6m flashband
2- 1 litre of primer
3- Exterior use clear silicone and mastic gun
4- Mortar (or a lead sealant)
5- Sharp flat blade knife
6- Paint brush
7- Scissors
8- Tin snips
9- Some lead for the clips and screws
So I hope this has helped and if you’re still not sure you can always call us to do it!

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