Construction in the category of simhah should be suspended during the Nine Days.

1. a. Construction, not for living but enjoyment (like a swimming pool, greenhouse, or deck), and painting, redecorating, should not be done during the Nine Days.

b. Only necessary construction for living purposes (i.e. kitchen, bedroom) is permitted. However, construction for a groom who has fulfilled the mitzvah of having children is not permitted since it brings excessive joy

c. If a great loss is involved in postponing construction until after Tishah B’Av it is permitted to proceed. For example if the home improvements cannot be postponed until after Tishah B’Av because there will be even greater damage if not repaired immediately and then will cost more to repair — such work may be done during the Nine Days

d. A non-Jewish contractor (paid by the job) working on his own schedule and who is not under contract to complete the work during this period it is permitted to proceed. It is preferable however, if the work can be postponed until after Tishah B’Av.

e. If workers were hired to complete the job before Rosh Hodesh Av and they did not, and now (during the Nine Days) if they do not work they will still have to be paid, the work may continue

2. Building, painting and redecorating a building used for a mitzvah i.e. a synagogue, yeshivah, mikvah is permitted. 

3. Planting bushes, flowers etc. should not be done during the Nine Days

4. The Nine Days are not an opportune time to move into a residence.