To start, I'd recommend the "5-" series Army Engineer Corps
manuals. You will find some great ideas there. There was also an anonymously
paperback book titled "Defending Your Retreat" (1978)
Press. I assume that
it is still in print. It includes good descriptions on placement of defensive
wire, (both concertina and tanglefoot) and one of the best discussions on the use of flares (trip flares and parachute flares) that I've seen in print anywhere. The second half of the book is a reprint from an Engineer Corps field manual. IMO, for a retreat house nothing beats living in a masonry, adobe, or rammed earth house with a fireproof roof. (metal or tile.) Ideally, if there are any exposed beams, they should be swathed in sheet metal to make them less vulnerable to Molotov cocktails. (You can paint the metal to make it look decorative.) The specifications for bulletproof steel window shutters and upgraded doors are described in my novel Patriots. The novel also mentions a handy formula for calculating the weight of plate steel. This can be important when considering what sort of hinges are needed, as well as the hoists and or jacks required for handling something that heavy. (I've found that a rolling engine hoist works well. The trick is to move very slowly and carefully, with lots of planning and communication/agreement on exactly what is planned by everyone involved before making the smallest move. A moving 200 pound piece of plate steel can be very unforgiving when fingers of toes get in the way--especially if it falling. Remember: 32 feet per second, per second!)
A few years back, I helped a friend design a slip-form concrete house with a native rock facade. The roof is metal, but it is there mainly there for show, since the house also has a 6" thick reinforced concrete roof, beneath. Since the house sits in a canyon, he only has to worry about one vehicular approach. There are abrupt four foot high terraces and "decorative" concrete planter boxes around the house that prevent vehicles from getting up close and personal. On a related note: A simple solution to the potential RPG/LAW rocket threat is also described in Patriots.