During the ministry of Jesus at Capernaum four men brought a paralyzed man to see Jesus, likely seeking healing, but there were so many people in the house that it was not possible to get in to see Jesus.
And when they could not get near him because of the crowd, they removed the roof above him, and when they had made an opening, they let down the bed on which the paralytic lay. (Mark 2:4 ESV)
Craig S. Keener describes the way the roofs of these houses were constructed.
The roof was approached by an outside staircase, so they could reach it unimpeded. The roof of single-story homes was sturdy enough for walking but was normally made of branches and rushes laid over the roof’s beams and covered with dried mud; thus one could dig through it. (The IVP Bible Background Commentary: New Testament)
M. J. Selman says,
Roofs were constructed from beams covered with branches and a thick layer of mud plaster, though the rafters were sometimes supported by a row of pillars along the middle of the room. Cylindrical stone rollers about 60 cm. [23.6 inches] long were used to keep the roofs flat and waterproof, though roofs needed to be re-plastered annually prior to the rainy season to seal cracks which had developed during the summer heat. (New Bible Dictionary, 3rd ed.)
The picture below shows a reconstructed house at Nazareth Village with a roof like the one mentioned above. Notice the beams made from small trees, the mud on the top, and some grass and weeds growing in it.
The next photo shows a portion of a roof made from wood and mud. You will also notice a roof roller on the roof. After the winter rains it was necessary to pack the roof with a roof roller. Roof rollers are commonly discovered during archaeological excavations.
But since they found no way to carry him in because of the crowd, they went up on the roof and let him down on the stretcher through the roof tiles right in front of Jesus. (Luke 5:19 NET)
Did you notice the reference to roof tiles? One of the Translator’s Notes in the NET Bible discusses this problem.
There is a translational problem at this point in the text. The term Luke uses is keramos. It can in certain contexts mean “clay,” but usually this is in reference to pottery (see BDAG 540 s.v. 1). The most natural definition in this instance is “roof tile” (used in the translation above). However, tiles were generally not found in Galilee. Recent archaeological research has suggested that this house, which would have probably been typical for the area, could not have supported “a second story, nor could the original roof have been masonry; no doubt it was made from beams and branches of trees covered with a mixture of earth and straw” (J. F. Strange and H. Shanks, “Has the House Where Jesus Stayed in Capernaum Been Found?” BAR 8, no. 6 [Nov/Dec 1982]: 34). Luke may simply have spoken of building materials that would be familiar to his readers.
There are other possible interpretations, but I hope this information with the photos will help you better understand the biblical text.