I'd approach survival horror as a survival story first. There would be situations that arise naturally out of the survival genre that you could change to be more horror themed. For instance, scary noises at night = zombies! Or something like that, good luck!
I believe that one of the key aspects of writing survival horror is being realistic within your world. If your characters are human, then they have to eat and sleep. If there is a supernatural or technological aspect involved, try to address it early on so the reader is not wondering why the main character is still running at top speed even though they haven't eaten in two weeks. And do your research in terms of what is edible and for how long because even Twinkies have an expiration date.
Survival horror is neat, though I can't think of many lit examples of it (Stephen King's "The Mist" is good). I suggest to play video games that fall under that genre to get a feel for the tone. Play lots of them - the ones that are scary, and the ones that aren't. Why is a game like Amnesia more frightening than Resident Evil 4/5? Why is the original Silent Hill scarier than Silent Hill: Homecoming? Gore isn't enough to make something terrifying; that sense of isolation and desperation is huge.
The one thing that I've always found useful when writing survival horror is being able to visualize the scene and what is going around within that world. If you can imagine it clearly, and give yourself a good scare, than you're on the right track I believe.