Fortress of solitude

This plan works very well in short outbreaks but will get harder the larger the outbreak becomes.

Fortress:

My fortress will be a old prison that is now used as a hostel. It is small but it is pretty much build like a castle. It has small windows with bars and a narrow entrance with sturdy doors that can be barred from the inside.

It has a yard that is shaped like a U that is surrounded with a old school prison wall with barbed wire
on top. The yard is rather small and you will need to make the best you can by making hanging gardens.

The layout within the building have 3 floors where the second floor open up towards the first in a way that makes it a perfect defense position in case of a breach.
the top floors have 28 cells with the original doors and windows. I plan on using some of them as quarantine cells for newcomers(if any). The yard have 7 houses erected for living that also reinforce the walls. depending on the internal layout this will either be used for living or storage. These will be scrapped for part as its needed.

Being a hostel with catering there will be a limited supply of food and drink (most important for variant A)

You can also temporarily clean the area from zombies by tricking them to fall into the water. (sketches and stuff to follow)

The execution of this plan have 2 scenarios depending on how much warning you get.

(Variant A) Ground zero version:

if it turns out that its a local breakout which also means it is a class 1-2 outbreak I will just run down there with basic survival gear. Food would not be a problem until a week and if the outbreak continues longer than that a scavenge plan needs to be made fast. (this scenario have a low probability compared Variant B since Patient zero will need to be right there. and there is no indication that this would be the case.)

(Variant B) Refugee version:

In this version you will get warning by news flow. you will have a short preparation period before the refugees starts to arrive.

I would use my savings to check into the hostel and start to hoard things in my room as well as briefing the residents and encourage them to do the same (people checking in to this place will have the same mindset). once the **** hits the fan you will be stocked with enough stuff to be covered for a while. once the first real outbreak occurs you will shut the door and trust the defenses. most people gathering at the harbor will ignore this place and aim for the many ships that is anchored there.

In both of these instances your "survival team" will be whoever happens to be checked in and present at the hostel at the time of "lock down". Variant B will be much more successful in this regard since you will be connected with people who obviously survived long enough to get there. Variant A is not as good but unless its summer it will be empty (not sure if its even open during the rest of the year). Friends and family will be encouraged to check in.

Fortress resources

water:

I am close to a limited amount of running water depending on season. being in a small city it will need proper filtration. there is also a small pond with stagnant water but fresh nonetheless. In a worst case scenario I will have to distill the ocean water. This will hopefully also provide me with salt for conservation of food.

Food:

space is limited (500m3) and constructions will be needed to maximize yield. There is some good land outside to grow low maintenance crops. Keeping animals will be difficult and gaining access to them will prove difficult in a urban environment.
My Prime source of protein will be in the form of fishing due to free access to the harbor. If I am lucky there will be abandoned ships in the harbor including fishing ships (being a island, it will be the destination of many refugees traveling by sea). If I am unlucky I will need to build a seaworthy ship. This is the least of my concerns tough since 5 years as a "sailor scout" have given me good understanding of buoyancy and sailing. The major problem with using fish as a primary source of food is the risk of contaminant in the oceans. Any disaster brings the risk of industrial accidents at the many chemical plants along the shores. That is why I will get a cat aka canary that will test the first catches. If the cat doesn't get spasms and dies the risk is acceptable. The yield of fish can only get better as the years passes due to the complete stop of commercial fishing.

shelter/storage:

the complex have 28 single cells with sturdy doors that will ensure privacy of all residents. there is also 8 smaller cottages that will be dismantled for building material in other projects.

Upkeep:

There will be no need for repair during its operation period (10-30 years). Heating will only be needed in winter due to the thick walls.

Energy:
I Plan on using a number of electronic devices and will need a power source.
My prime source will be wind power and I am fairly confident that I will be able to constructs most of the vital components. I have no formal education in electrical stuff and further research is needed.
My secondary source will be solar panels transplanted from other roofs (I am mapping them as I find houses close to the fortress). Hopefully I will be able to salvage at least a small number of panels but due to weather conditions the power output will be much smaller than the wind.
I will use a basic battery bank taken from abandoned cars. There is a car rental storage across the road. It is a gold mine if it is left intact. it also contains untoward 150 bicycles for summer tourists.