So to be clear, I'm not trying to model spread. I'm taking a pretty different approach which is to look at metrics I can derive from an entire network, like centrality and modularity, and use those to predict the overall probability of survival. I'm not trying to say where or how a fire might progress through a network, but rather looking at the overall structure of a network at, for example the parcel resolution, to estimate the likely hood that a given structure might survive a wildfire.

So in the above figure, (it was literally a screen cap of what I had on at that moment, so no effort into graphic design etc.), the diameter of the circle corresponds to the exposure, which is weighted by the total facing. The units on the edges are kilojoules per m^2 per 300 seconds. The circles are on the 'receiving' side of the network (this is a directed kpartite network, and we're only looking at structure:structure edges).

So you can imagine that if you stand with your face to a campfire, you receive more radiation than if you stand edgeways. Likewise if you take a step back. Same principal. I'm not adjusting the edge weights for structural composition or construction (although I'd like to. in the metaphore, all the campfires are the same size and intensity). This is just assuming that each structure will put out about the same amount of energy when burning. However, because of the physical arrangement of things in space, they do not necessarily all experience the same exposure. We can use those differences to create a set of weights, and then by looking at how 'modular' the system is at a given exposure rating (IE, how fully connected is the graph at a given kJ/m2), we might find that the network breaks into some interesting or predictive components.

So, very long answer, but trying to make it shorter: I'm not trying to model spread or predict how fire would move through this system. I'm trying to come up with an overall probabilistic assessment or risk based on how 'connected' features are in space.