Trained Eye

 
 
 

Peeling Paint

Question:

For today’s column we have two questions about peeling paint, in different situations. They will be answered together.

Dear Mr. Marantz:

Thank you for providing an opportunity for finding information for the homeowner.

I painted my steel door, some years ago, over the factory primer and this past summer the paint began to peel, right down to the shiny metal. The small panel adjacent to the door is also peeling. I used Tremclad paint and for some reason it has failed. I have now bought more of the same and also the primer and am wondering if that is the right paint. I also want to know how to go about applying it. Do I use paint remover to completely clear the door and panel and then wash it down with TSP before starting in with the new coats? It is a project I don’t look forward to and have successfully put it off until I have to tackle it this spring.

I would very much appreciate any advice you could give me.

Thank you very much.

Dear Mr. Ari Marantz

I live in a house plagued with peeling paint. The house was built in 1960 with walls of plaster over drywall lath. I believe the original paint was latex, but oil has been used over that. I would say my winter humidity is low. Peeling occurs all over the house, on any interior or exterior wall and some ceilings. In most cases, I can’t understand why the paint peels. In some cases there are attributable causes. I also have major trouble on my kitchen ceiling which was water damaged by a previous occupant. The kitchen ceiling plaster appears flawless, so I’m not sure what is going on there.

Peeling is always right down to the plaster, which is always smooth, normally coloured and appears sound. Some repairs are successful but some peel again in exactly the same places. Some peeling is in places previously exhibiting no problems. Peeling shows up anywhere from months to years after painting. It ranges from coin-sized patches to chunks the size of dinner plates.

My prep work is meticulous and I use good quality materials. I usually use latex primers, although I may have tried alkyd in desperation. I haven’t discovered a pattern to what works and what doesn’t. I need a solution before my paint roller becomes an extension of my arm. My question is; how do I paint bare plaster so that it will never peel again?

Answer:

To answer these questions, I have consulted journeyman painter Don Moulden, of Moulden Painting and Contracting Services for proper techniques to solve these problems.

For the first steel door, it appears that she is on the right track. The door should be stripped of all paint, down to the bare metal, before cleaning and priming. Once clear of all paint the door should be cleaned first with Tri-sodium phosphate (TSP) and then cleaned again with lacquer thinner. Once clean and dry, Moulden strongly suggest priming the metal door with a zinc-based primer or one with high zinc content, for proper adhesion. The Tremclad or other paint designed for metal surfaces should be fine for finish coats, once the primer has properly dried.

The solution to second question about peeling paint is a little more complex. The reasons for the failure of the paint to stick to the plaster may be difficult to pinpoint, but the main problem is that the original primer has lost its ability to adhere to the plaster. As successive layers of paint and patching are added and moisture is absorbed, over many years, the primer cannot hold on to the plaster, and may peel off in large or small chunks. Moulden states that the failure may be due to original preparation, poor priming, or other factors, but properly repairing the walls and ceilings for repainting should be the focus.

All loose paint should be peeled off the walls and ceilings with a putty knife, or other thin blade, to expose as much of the original plaster as possible before proceeding. Once all loose material has been chipped off, the edges of the sound, unpeeled areas should be sealed with an oil-based primer. Moulden stresses that this is critical to prevent the new patching material and paint from transferring moisture to the old paint. If this happens, the old paint may peel shortly after repainting. This is the likely cause of the repeated peeling experienced by the first homeowner.

Once the edges are well primed, they may be filled with drywall compound or other patching material and sanded smooth before repainting. These newly filled areas and all bare plaster should be further painted with oil-based primer to ensure proper adhesion of the new paint. Once this is complete and fully dry, the finish coats may be applied and should remain in good condition for a long time.