Hi - been there done that! Start again! OK I can see there is enough clearance below the door to allow a decent fall to be created if its not enough already. This can be done using pressure treated timber firings which are essentially lengths of timber cut and tapered to dimensions according to a plan such as my example below (I realise your balcony is much smaller but you should get the idea). My firrings plan and cutting list shows 3 drain points with the firrings mitred to created falls toward relevant drain. Your local timber supplier should be happy to cut these and pressure treat resulting tapered timbers which would be fixed at 300 centres max and would have 20mm min marine plywood screwed on to them at 150mm centres. OSB 3 roofing 'chipboard' which can come in tongue and groove form would also work, I just prefer ply. They need to be planned out so that the fall of the timber firrings sends any water toward the drainage channel (if there isn't one then create one) or to the edge of your balcony where the rainwater gutter will collect it. Then use RESITRIX - we used this supplier, but there are plenty out there.... http://www.rubber4roofs.co.uk/shop/epdm-rubber-roofing which is a much stro nger version of EDPM rubber and can withstand foot traffic as it is reinforced with fabric making it almost like a wet suit - its a fantastic quality product believe me!. You paint on a black primer on to the ply, then peel the backing off the RESITRIX and apply. Be warned - as experienced people (but not exactly specialist roofers) we managed to do this very effectively, but found that extreme care is needed before committing as once the RESITRIX makes contact its sticks forever!! this is especially difficult at internal corners. Only peel back the backing plastic off the RESITRIX rubber a little at a time as you need to hold it up off the deck to ensure it doesn't make contact in wrong place. two pairs of hands can help!!If you have planned the falls correctly so that the water is sent to the drain, you will now have that long awaited water tight balcony! Now Google 'tiles for decks and balconies' and you will find no end of options of special porcelain or ceramic tiles with plastic adjustable feet for each corner of tile which allow you to place the feet and tiles level on top of your RESITRIX flat roof with no risk of penetration pif the rubber. Water goes between the tiles as they are not grouted, just placed on the feet. Not sure if the tiles you have will work without cracking - you could test this by standing on one which is supported only at corners. by the way RESITRIX happens to be one of a range of flat roof solution I have used including Kemper liquid rubber system (which is reinforced by a fleece like fabric which is simply rolled out onto a bed of liquid rubber then soaked on top with more rubber) Messy but effective, a similar process to GRP. Have also used one piece EDPM rubber which a very competent DIY'er can fit. A very economical and speedy solution, but not good for foot traffic - although they are starting to introduce reinforced versions. We are actually going to use slate grey plastic/wood composite decking http://www.wpc-decking.co.uk To do this we will PLACE a new set of firrings on top of the completed rubber deck but also will stick strips of RESITRIX to underside of firings for protection. now we will have a deck that can be lifted for maintenance in future if required. These firrings are the opposite of the ones used to create the falls, which brings the deck back to level of course! In reality we will actually adjust to maintain a slight fall so that, and the gaps in the deck takes water away. A long answer - I hope that it helps! Best of luck! Nick Wall Design + Build 07745581167

Hi original poster! I know it’s 7 years since you asked this but would love to know what you did. We are not in a similar position with a similar looking house at the back but even steeper. I know that a full extension and lowering the internal floors would be ideal but we can’t afford that and need a 5-7 year fix. Please let us know what you decided and why ☺️

If you're leaning more towards a pitched roof, perhaps you could extend your glazing right up into the gable to maximize the light coming in. I've attached a couple of images of projects where we have done just that. The first was necessary due to it being a listed building so we suggested an additional tiled roof would be more in keeping than, for example, a flat roof with a roof lantern. The second was on a lovely Victorian terrace in Coggeshall and again, we suggested echoing the original architecture with a pitched roof and glazed gable. If you would prefer an orangery style extension, despite some previous comments it is definitely possible to have a space that is a nice even temperature all year round, doesn't collect lots of flies and doesn't leak. We have built these for 30 years. All of our roof lanterns are available with solar controlled glass and motorised vents, plus the combination of masonry and glass (as opposed to a traditional conservatory which is mostly glass) provides a a more consistent room temperature anyway. We offer a 10 year guarantee on our joinery, glass and paint coatings (parts and labour) - that's how confident we are that it won't leak. We also use Accoya wood in our products which is incredibly durable, stable, moisture resistant, fungus proof, inedible to insects and thus incredibly low maintenance. It's definitely worth googling Accoya if you're considering going for a structure that incorporates timber joinery.

@ Gabby - you were told wrong as it is not okay! I have been building everything from houses to retail centres and the problem with damp/water penetrating the void is that it takes a very long time to dry out especially if a rockwool type insulation has been installed. What is more you can also end up with mould growing in the void. It was sloppy workmanship and for the sake of a few minutes work the builders have an issue to deal with that should never have been. The amount of water showing on the face of the blockwork gives you an idea of the scale of the issue so do not be kind to them about this as it could come back to bite you in the behind in the future. If I was managing your project I would insist that they use the water resistant plasterboard (green in colour) to line all of the walls. This is a strong recommendation on my part.