There are several ways in which to encourage house martins to nest in your home. The easiest way is to allow a small area of your garden or your local community to be bare mud so that house martins have their nesting material ready to use.
It is possible to attract house martins to nesting on your property by attaching an artificial nest in a suitable location on your property. For most people, this would be under the eaves or the gables of a house. One can buy ready-made house martin nest cups made from suppliers such as Schwegler.
You could get creative and make your own house martin cob home!
This is how to do it: Take a handful of mud (the best kind is a loamy or clay mud), a handful of sawdust or hay, and a cup of pollyfilla powder. Mix the mud, sawdust/hay, and pollyfilla together with water until you get a thick paste – your cob.
You will then require a cardboard bowl that is about 13cm deep and has a 24cm diameter. It helps if the bowl has a lip. We found that standard issue sick-bowls are brilliant, but any cardboard bowl will do. Cut the bowl in half, and then cut a small entrance hole into the top edge. Spread the cob onto the inside of the bowl, to a depth of about 1cm thick, including the lip of the bowl, taking care to leave the entrance hole free.
Place your cup to a piece of plywood, pre-cut to 20cm high and 30cm wide, with four pre-drilled holes in each corner. You can attach the cup either by gluing it to the wood using wood-glue, or you can staple the cup to the wood with a staple gun.
Paint the outside of your cup with some diluted mud to make it brown. Let the whole mixture dry and then attach to your desired location.