Nest Site Provision for (mainly) Sparrows - Questions

Hi -

We're having loft conversion work on our house.  Currently we have some sparrow families nesting in the roof space.  When the work is done this nest site will be gone.  We'd like to provide an alternative.

The two most obvious options - given the planned architecture -  are: 

  1. Place external Sparrow Terrace boxes on the back of the house at about the same height as the current eaves.
  2. Build in more permanent Sparrow Terrace structures (e.g. brick fronted boxes made of concrete/woodcrete) into the external wall brick skin at the same height.

Is there a eason why we should choose one over the other (other than aesthetic)?

Does anyone have experience with the built-in boxes and can you recommend a make or type of box?  Are there any drawbacks to this choice?

Thanks for your help with this.