In article , "Pete C." wrote:

I agree that the OP should check the back of the siding. I do not
however consider a lack of discoloration on the back side to be
conclusive proof of an external heat source

What *would* you consider to be conclusive proof that you're wrong? You don't
even consider a *photograph* to be conclusive proof that you were wrong about
the discoloration on the siding.

since one side is in free
air and the other in confined space which could affect discoloration.

Indeed it could -- the side in free air and away from your presumed heat
source would be much *cooler* and therefore much *less* likely to be
discolored.

Based on the lack of conclusiveness of the discoloration, the evidence
supporting an internal heat source such as the damage to the siding that
extends past the railing where any likely external heat source would not
reach,

That argues against an external heat source. It does *not* argue *for* an
internal heat source.

the more significant damage to the Tyvek,

???

The damage to the siding is *much* worse than the damage to the Tyvek.

and the positions of
electrical boxes and a suspect nail, an inspection of the interior of
the wall in that area is more than warranted.

The risk of inspecting inside that wall and finding nothing is at most
an hour of wasted time, the risk on not inspecting that wall and not
seeing fire damage that is there is the risk of a reoccurrence with more
devastating results.

I'll take your bet -- you said 95%, I think, that the OP will find evidence of
a fire interior to the wall. That's 19:1 odds -- I'll take that, and be happy.
What are the stakes?

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.