Will the Isha and taraaweeh salaah be valid if Performed on the roof of a Masjid?

Q: Salaah-238: During the summer months, we perform the Isha and Taraaweeh salaah on the roof of the Masjid rather than inside. Is there any harm in this?

Answer: To perform the Isha and Taraaweeh salaah on the roof or in the courtyard of the Masjid rather then inside is Makrooh. It will, of course, not be Makrooh for those people to perform their salaah there who cannot find place inside the Masjid.

Nissabul Ihtisaab (pg.32) states that it is Makrooh to perform salaah on top of the Kabah or to climb on the roofs of Masaajid (because it is disrespectful) unless it be for repair work. Similarly, it is also Makrooh to perform salaah on the roof when it is too hot inside the Masjid. This will be permissible only when there is no space in the Masjid, in which case it will not be Makrooh out of necessity. Excessive heat is not considered as a necessity but is an inconvenience because of which the reward for the salaah will be greatly multiplied.

The same is stated in Fafaawaa Aalamgeeri (Vol.5 Pg.322), Kabeeri pg.392, shaami (Vol.1 Pg.614), Majma'ul Fataawaa (pg.140 and Naf'ul Mufti was Saa'il pg.121.
There is however no harm in performing salaah in the courtyard of the Masjid during summer. If any portion of the courtyard is not part of the Masjid, the person who built the Masjid or the people of the congregation may include it in the Masjid. The laws of the Masjid will then apply to it as well. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2