Welcome, and thank you for your question.
In property law terms your neighbour's actions are referred to as a "nuisance". If speaking to your neighbour about it does not work, the remedy for a nuisance is to approach the competent Court for an interdict. The requirements for an interdict are relatively straightforward: it is up to you, the applicant, to allege and prove
- that you have a clear right to the remedy (not to have to content with your neighbour's smoke; health; etc.),
- that your right in 1) is being infringed or is threatened by the respondent,
- that the infringement or threat is unlawful and
- that you have no alternative means of achieving the remedy other than to approach the Court for relief.
Giving a clear history of events will go a long way towards meeting the above requirements.
The law of nuisance is actually quite well developed here in SA, and there is a wealth of precedent upon which you will be able to rely. The Court will likely have to balance the respective rights that you and your neighbour rely on and make an order that is fair under the circumstances. The fact that raising the chimney is a relatively simple and cost-effective solution to the problem will weigh in your favour.
Ideally, you should instruct an attorney in your area to represent you in respect of the application for an interdict as the process may become somewhat technical. The cost, I'm afraid, is difficult to predict as it may vary from one attorney to another and also whether the neighbour opposes the application or not. A rough estimate would be somewhere between R20 000 and R50 000. There is of course the possibility that if the court grants the interdict, it will also order the neighbour to pay your legal costs (or a substantial portion thereof).