Interior Painting: flat over semi-gloss

I've heard conflicting opinons on preparing to paint over semi-gloss. My apartment walls are plaster with a coat of white semi-gloss. I'd like to apply a new coat of flat brick - should I sand, use TSP, or degloss. In addition should I use primer? Thanks in advance.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Wash with TCP using 2-3 tablespoons in 2 gallons. It will slightly degloss the semi-gloss paint and provide a tooth for the new paint to stick. You need to do this no matter what kind of paint you put on top, and you don't need primer. I just use an old wash cloth. I use only semi-gloss on the walls in my house and have had no problems over a 27 year period of ownership. If the color change is great or you go from dark color to light, you probably will need two coats.
squeaky88th wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.