Bee hive removal is a specialist area. Looking on YouTube may give you some ideas but it’s the experience you need in safely removing bees. Bees can become very aggressive and dangerous if not handled properly. Get a professional. They carry insurance.
When a bee swarm enters a wall cavity or some other structure they set about making wax and gathering food as soon as possible. Within a few days there will be a supply of nectar and pollen and the queen bee will have started laying eggs. The bees have a new home and, just like you, they will defend it.
The number of bees will build up quickly and the amount of honey and stored pollen will also increase quickly after a few months.Once a bee colony has been in a wall for a year there may be as much as 40 -60 kg of honey in the wall. We regularly remove 60 -80 kg of honey from wall cavities and have removed over 200kg from a particularly big hive in one building.
When jobs are done by amateur beekeepers or pest companies they may make a short term fix surface level but often long term issues behind the wall arise such as mould, slime seeping from walls and floors, and repeated re-colonization by bees are some of the common issues we see when we are called to fix problems others have left.
If the hive is left in the wall insect pests like wax moth or small hive beetle will invade the hive and destroy the honey combs and the honey will run. Sometimes it goes down into the foundations but often it bleeds through the wall and occasionally it ruins floor coverings. Small hive beetle can be a serious pest. It ferments the honey with a yeast (Kodamaea ohmeri ) which can be dangerous to people if they are immune compromised or have respiratory issues. It is this yeast that causes the honey to turn to repulsive slime.