[If] one rented a house to another, and it collapsed, he is required to provide him with a house. [If] it was small, he may not make it large; [if it was] large, he may not make it small; [if it was] one, he may not make it two; [if it was] two, he may not make it one; [and] he may not decrease the [number of] windows, nor may he add to them —- except by common agreement.