Construction material is one important need for long-term habitation on the moon. Solar radiation, when concentrated for high heat flux, can heat lunar soil, or regolith, until it sinters at temperatures above 900°C. The solid, sintered regolith can be used for construction material. This work explores the conditions which lead to effective sintering of lunar soil for both directly irradiated sintering and indirect sintering. Lunar soil simulants were sintered using concentrated light from a xenon-arc lamp with varying heat flux intensity. The resulting depth of sintering, amount of material sintered, and the compressive strength of the sintered material were recorded. A sintering range of 860°C–1140°C was identified. Limited compressive strength data showed higher strength for indirect sintering.