Door opening detail on timber frame build...

[Carrerahill]

Just looking for some images or help regards the door opening detail for my timber kit extension - our build is a little odd as we already have a sun room in this part which will form part of the new extension, so I am reusing the door opening. At the moment it leaks down the outer skin into the cavity, but that is because the builders who built this have used a piece of ordinary concrete slab along the top of the block wall that the door sill sits on, however, they then laid slabs up to the same height as the door sill, so water must just pour down the gap between the slab and door sill, and flood in under the sill over the piece of concrete slab and into the extension! They were clearly cowboys or got their levels all wrong and didn't want to resolve it - the bead of silicone along the slab to and sill shows that someone did see this as an issue!

 

So, in my new extension the door will end up moving in slightly as it will sit flush on treated 50x50 around the opening in the timber kit then the block work will come up to the edge of the frame and get rendered in.

 

I am going to be modifying the suspended timber floor at the weekend and want to prepare the door opening at floor level during this time - can anyone show through images or details they may have how I do this. 

 

This is my plan, for now, based on best practise:

 

Install a concrete sill on top of the outer wall, assume no DPC under it so it can drain, I may possibly pour this in situ with a run to exterior and higher than the slabs obviously.

I will order a door with a stub sill and this will sit on the concrete sill and end up sealed in.

Around the door the render will come up close then get rendered or I will use a render strip and seal it all.

So externally there should be no route for water to get in, and any seepage under heavy rain or someone hosing the door or something daft would only result in some water possibly getting in behind the render, down the frame and into the cavity, even at ground level water should not not in as it will run off the sill.

 

Internally I will bring the floor up to the inside of the door frame, this will bring it to the edge of the inside of the cavity, where the door frame will then start. This means there is no bridging except for the door frame itself but sitting on it's own stub sill and then the concrete sill all water will run away from the door - I will also reset the slabs outside the door which are at the top of some stairs with a very slight run away from the house - at present they run in the way and thus under the sill!

 

Does that make sense and sound right? I know it is such a simple detail but only if you have seen/built one before do you know your install is deemed common practise and not just my best practise guess!