Ruling on using donated money to finish preparing the charity organization office
Question

                We established a charitable organisation to sponsor orphans in the province in which we live, but we were not able to establish the office for financial reasons. Our question is: is it permissible to use some of the donations to complete the building of the office?.
Praise be to Allah.
    Firstly: 

    The money that the charity has received must be one of two 
    things: 

    1.Obligatory charity (zakaah)

    2.General charity (sadaqah)

    It is not permissible to spend zakaah on anything other than 
    the eight categories defined by Allah, may He be exalted, in the verse on 
    how zakaah is to be spent; they do not include building mosques or Qur’aan 
    schools. We have discussed this previously in the answer to question no.
    21805 

    With regard to general charity, there is no reason why it 
    should not be spent on any charitable cause, which includes building a 
    charitable institution to take care of orphans, unless the one who donated 
    the money stipulated a specific way in which it was to be spent, such as 
    sponsoring orphans, for example. In that case it is not permissible to spend 
    it on anything else. 

    Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was 
    asked: 

    A man gave someone some money to spend it on a school for 
    memorisation of the Holy Qur’aan, but this person collected some of this 
    money and bought a big car and said it is for the school, but he registered 
    it in his own name. What is the ruling on this action? 

    He replied: 

    Firstly:… 

    Secondly: this has to do with the way in which the money he 
    was given is spent. If it was for the general interests of the school, there 
    is nothing wrong with buying a car if it serves the school’s interests. But 
    if the money is specifically for the teachers and students, then it is not 
    permissible to spend it on anything else.

    End quote from Majmoo‘ Fataawa Ibn ‘Uthaymeen, 4/330 

    He was also asked (may Allah have mercy on him) 

    There is something called “winter blankets”, which some 
    charities collect and distribute to some Muslims who live in cold regions. 
    These charities collected the blankets to keep the Muslims warm; is it 
    possible to expand this work because the aim is still to keep Muslims warm, 
    and in some places the poor need winter clothing, for example, or they need 
    stoves and the like to keep warm, so that would be bought with the money 
    that was collected to buy blankets, because the aim is the same, which is to 
    keep Muslims warm? 

    He replied:

    It is better to call this charity “Winter aid”. If it is said 
    that winter aid could apply to blankets, clothing, stoves and other things, 
    then it is better to change the slogan under which collections are being 
    made, and call it “winter aid” or “winter protection”. 

    With regard to that which was collected for a specific 
    purpose, it should not be spent on anything except this specific purpose, so 
    long as it has not become redundant. If we have bought winter blankets for a 
    particular village, and that used up only half of the money collected, but 
    they need clothing or means of warming themselves, then there is nothing 
    wrong with spending the remaining funds on that. But if all the money is 
    required to cover the need for blankets, then it is not permissible to spend 
    it on anything else. 

    Questioner: But some people need clothing to keep warm, and 
    they do not need blankets. 

    Shaykh: Yes, but the slogan or name of the campaign specified 
    blankets, and the people need them. 

    Questioner: But the aim is the same, if blankets are replaced 
    with something else. 

    Shaykh: But that is not right at all. 

    But if it is well known among the people that what is meant 
    by “winter blankets” is winter aid, then that may be acceptable. Therefore 
    it is better to change the slogan from now, and call it winter aid or 
    something similar. 

    End quote from Liqa’ al-Baab al-Maftooh, no. 43 

    And Allah knows best.