Iâ€™m not sure if by â€œrental houseâ€ you mean the home you are renting or the home you own that you rent out â€¦
Answers will be different for each. First all, the explanation:
The issue with mold is determining its cause. Itâ€™s not enough to simply clean it and hope for the best. Mold originates with moisture â€“ find the source of the moisture and you will usually locate the source of the mold. To eradicate mold, you have to treat locally, replace any infected materials that have been damaged AND remove the ongoing source of moisture.
In some cases, itâ€™s a very simple fix. In other cases, it can be a huge issue and youâ€™ll need to call in professional help.
In the case of mold under carpets, it could be from constant spills, pets and moisture from above. Itâ€™s why you should NEVER install carpeting in a bathroom or kitchen. Surface moisture will more than likely result in the need to replace the carpet â€“ Iâ€™m guessing you were doing just that when you found the mold. In addition to replacing the carpet, you need to make sure you are not getting any moisture from below. Standing water in a crawlspace or leaky pipes in a concrete slab will frequently translate to mold in the floor above.
After you are SURE the moisture source has been dealt with, allow the area to completely dry, treat the area for mold (ensuring you use a fungal inhibitor on the surface) and replace any damaged surface materials as required.
Which then brings up the answer to your question:
If you rent â€“ contact your landlord and ask that the area be properly dealt with and certified free of mold.
If you own and there are currently renters in the property, they may ask you for a certificate. If the property is vacant, then as long as you can guarantee that the mold has been completely and properly dealt with, then you should not need a mold certificate.
If you have any other questions, check the following link from the City of San Jose â€“ go down to the section entitled â€œWatch Out For Mold and Mildew.â€