Taking compass readings inside a unit

For some, it can be quite a nightmare taking compass readings as most built up areas have lots of embedded re-inforced steel bars - that will often cause the readings to differ greatly from various locations within a premises.
Nowadays, especially in Singapore, which is close to the equator, the True north and magnetic north is the closest; one may consider using a tool like electronic maps from sites like: onemap.sg which uses the official govt. survey maps.
Another useful tool is to purchase a good quality protractor.
As all street maps both paper version and electronic automatically shows a layout in relation to North-South, try to look for the sitemap of the building. Most good quality maps will have the outline of the building. Try to determine the facing direction and check out the compass degree from here.