The plumber and electrician opened up the walls. How are they closed so nothing shows?

When the plumbing or wiring is changed, the new pipes and cables usually go inside the wall, in chasesWall chaseA groove cut into a wall so pipes or cables can run inside it. Afterwards it is closed with mortar or render and, once finished, cannot be seen.. Once they are fixed firmly, the chases are filled with mortar or plasterRender (plaster)A layer of mortar (sand, cement or lime, and water) spread over brick or concrete to give a wall a straight, sound surface ready for paint or tiles., in more than one coat if they are deep, until they are level with the rest of the wall. Where new plaster meets old, or the chase is long, meshReinforcement meshA mesh or fabric, usually glass fibre or polyester, set into render, a coating or liquid waterproofing to hold it together and stop cracks from opening. helps stop a crackCrackA split or gap in render, concrete, a wall, a coating or wood. Fine cracks are usually only on the surface; ones that grow, keep reopening or run diagonally need attention. opening later.

In one kitchen, after the old tiles and units came out, the new water and electrical points went where the new kitchen needed them. The openings were closed up and the walls were plastered, straightened and painted. All that was left showing of the pipes and cables were the outlets, exactly where the appliances would be connected.

The finish is the same as for any other wall repair: fillerFillerA fine paste or powder that fills holes, fine cracks and dents so a wall, ceiling or piece of wood is smooth before it is painted., sandingSandingSmoothing a surface with sandpaper or a power sander to remove bumps, loose old paint or gloss, so the new paint or varnish grips well and comes out smooth., primerPrimerThe thin first coat that goes on before the main material. It binds dust, seals the pores and helps paint or waterproofing stick firmly. on the patched areas and paint, preferably over the whole wall, because a patch painted on its own usually stands out.

Keep in mind: before the chases are closed, check that the pipes don't leak and photograph where they run. Agree beforehand who closes the walls and who paints. And if the wall was opened for a leak, let it dry before it is painted.