The warning has been issued by Sandwell Council which has concerns about the issue within the borough.
The local authority's consumer protection team fears there may be illegal activity; including false representations, unreasonable charges, unfinished poor-quality work and aggressive practices.
A spokesman for the council said: "With the weather improving, we tend to see an increase in rogue trader activity, particularly around works to roofs, driveways and gardens.
"A lot of these rogue traders use intimidating and aggressive behaviour to persuade residents to agree to work.
"We’re urging people to keep a particular eye on their elderly and vulnerable neighbours, who may be having work done.
"People can report suspicious activity to us or get advice by phoning 0808 223 1133."
The council has advised people not to have work carried out on the spur of the moment.
It is recommended to get several quotations from traders for building projects, with a minimum of three.
It is also advised to have the name, address and contact details of the traders involved; while people should not hand money out in advance.
An easy way to make sure traders are reputable is using the Buy with Confidence scheme.
Consumers looking for a gardener or home-improvement tradesperson can search the register themselves at www.buywithconfidence.gov.uk or call 01392 383430.
The scheme is not designed to approve particular traders, but all joining the scheme agree to abide by the scheme’s code of practice.