No mortar was used. The blocks and slabs simply rest against one another, as they have for centuries, which makes the survival of even this much of the structure quietly remarkable.

The building is of two-period construction, meaning it was not raised all at once but grew in stages. What appears to have come first is a small oratory, a compact space used for prayer, measuring internally around 5.3 metres by 3 metres, which now forms the chancel, the eastern, liturgical end of the church. At some later point, a larger nave was added to the west, extending the interior to nearly ten metres in length. The join between the two phases was evidently not seamless: at the south-east angle, an internal buttress appears to have been inserted specifically to address a gap that opened up between the nave and chancel walls at that point, a small piece of medieval problem-solving made visible in the stonework. The original entrance was at the west end, and a second doorway, marked by a gap of about a metre, sits towards the south-west angle of the nave. No trace of windows has been identified anywhere in the surviving fabric.