Thuja plants belong to the cypress family and are shallow rooted, i.e. the root system spreads relatively close to the surface. In Europe, thuja are often also called tree of life.
For a hedge directly at the house, you should keep a distance of at least two meters. However, you can reduce the distance with a so-called rhizome barrier. A very thick and root-proof plastic foil (thickness approx. 2 to 3 mm) is suitable as a rhizome barrier. You can buy these foils in pond supply stores or in larger garden departments of hardware stores. The root barriers should be buried about 70 to 80 cm deep into the soil. They thus protect against spreading towards the side of the house.
Certainly, the distance could then be reduced to one meter. Plan some space for a path behind it for maintenance. You also have to think about the proportions over the years: an annual growth of 10 to 30 cm (depending on the species) in height is normal. In width, the plant grows a little slower, only 5 to 10cm. More about care and pruning you can find here.
