Paul:
Sorry don't have time to look it up as this is a grey area for me - the HUD4150 as originally writ had little local options according to your local HUD office, since centralization, the rules have changed, and this is not one of the items I am currently 'up on' nor have I time to research it today, I offer you the following advice set:
You may want to post this query on the HUD FHA forum, however you may get conflicting and inaccurate advice....
1 call your local building code enfrocement agency (assuming you live in an area where such exists, and ask them what is the current firewall requirement or if it is grandfathered. If no agency has jurisdiction, forgett it - no longer important.
2 The HUD tech Support line # in Denver (only area I know-and your area may have a differnt ruling on this matter: as who to cal first~!) +1 (800) 543-9378 ext. 5217 Ask there with full explanation of what situation is: liveing area above garage, what is required... I beleive that there is no longer a specific HUD requirement but do not want to steer you wrong.
3 oh this IS nasty: ask the appraiser to provide you with the documentation or source for his request.
It is not at all uncommon to have individuals doing HUD/FHA confused as to what the current set of rules are for FHA! Even the experts at HUD can give you three different rulings on some matters.... DO write down who you spoke with, the time, and exactly what they said, treat it as you would a call to the IRS in terms of documenting...
again, good luck.