Building
The pitfalls of dealing with building, renovating and maintaining a property in Galle, while in many ways the same as anywhere, but in some ways it is very different.
The climate
The Sri Lankan climate is very hard on metals: anything that can rust, will do so far more rapidly than most places. This is all the more true if you are close to the sea. Avoid using metal window frames etc. Reinforcements buried in masonry are widely used and are fine.
Galle can be very hot. Avoid large glass windows (a mistake made by many Sri Lankans!) and ensure lots of ventilation. Houses in the Fort tend to be cool because of their thick walls, courtyards, and the absence of direct sunlight. You can learn from that.
Selecting a builder
First and foremost, find about their reputation. It is not difficult. It should be possible to see houses that they have previously built or renovated, preferably ones a few years old to ensure their work lasts.
You are likely to be faced with a sales pitch that suggests you cannot go directly to a Sri Lankan, because they will not work to "European standards". It is true that most Sri Lankan houses in Galle are not well finished, but this reflects the limited budgets of most people a city far less prosperous than, for example, Colombo.
In addition, most of the non-Sri Lankan builders sub-contract all the actual work to a Sri Lankan. You are adding an extra middleman to check up on things, at a high rate.
A more real problem is that you may be restricted to people who speak English, or you need to arrange to have someone who understands Sinhala ensure that your requirements are understood. We can help with that.