To control a rat effectively you need an integrated plan. This planned approach should combine many things. Including prevention, proofing, good housekeeping, and legal control methods.
In residential settings, internal rat issues are often the result of a fault/weakness in a drainage system (note the video link below). The problem with this, that fault/weakness can be very elusive. The rat issue becomes very prolonged. We have a lot of experience tackling residential rat issues. We know where and what to look for. Sometimes though, your home is in a terrace - for example. Often it's not possible to find where the rodents are coming from, without a thorough drain survey. In a terrace you only own part of the building. You will need others in the terrace to join forces, so all areas can be checked. This means you may not be able to resolve issues in those areas you don't control, if others aren't interested.
In commercial and industrial settings, rat issues need a detailed, consistent and structured pest control approach. We are also very experienced at this. Don't take our word for that. Please ask and we can give you some references to call. Feel free to ask them what we did for them. So often in industrial and commercial settings we come across poor pest control. Often also being done illegally. This exposes the client to prosecution. Don't take a chance - give us a call. We will quickly help you understand the key things to be aware of. To control any rodent problem.