{"id":20297,"date":"2022-11-17T09:44:42","date_gmt":"2022-11-17T07:44:42","guid":{"rendered":"https:\/\/www.klicarquitectos.com\/how-to-insulate-an-existing-roof\/"},"modified":"2026-09-06T02:55:08","modified_gmt":"2026-09-06T00:55:08","slug":"how-to-insulate-an-existing-roof","status":"publish","type":"post","link":"https:\/\/www.klicarquitectos.com\/en\/how-to-insulate-an-existing-roof\/","title":{"rendered":"How to Insulate an Existing Roof on the Costa del Sol"},"content":{"rendered":"

The roof is the most exposed part of any house, and usually the first to complain. Sun, salt in the air and the odd autumn downpour wear the structure down, and a tired roof stops doing the one job you actually notice: keeping the house comfortable.<\/p>\n

On older Costa del Sol properties the problem is rarely a dramatic leak. It is a roof with little or no insulation, so heat escapes in winter and pours in all summer, and the air conditioning runs hard just to stand still. Done properly, the roof is the best piece of thermal insulation a house can have, because it works for you at both ends of the year.<\/p>\n

Which is why clients keep asking us the same thing: how to insulate an existing roof<\/strong> without pulling the house apart. There are two ways to go about it, and they are genuinely different pieces of work:<\/p>\n

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  1. Insulating the roof from the outside.<\/li>\n
  2. Insulating the roof from the inside.<\/li>\n<\/ol>\n

    Here is what each one involves, and when it makes sense to choose one over the other.<\/p>\n

    Insulating a roof from the outside<\/h2>\n

    Working from above is the better option if the building is lived in. The trades never have to come through the flats, and daily life carries on more or less as normal. Three solutions come up most often:<\/p>\n

    Expanded polystyrene (EPS)<\/u>: normally used when there is no access to the void beneath the roof, or when the tiles need replacing anyway. The polystyrene boards are grooved on top so the tiles sit properly and do not slip over time. It is worth leaving a vent in the roof so that water pressure equalises inside and out, which is what stops condensation forming.<\/p>\n

    Spray polyurethane foam<\/u>: very useful where water is already getting in. It goes on quickly and it is one of the cheaper routes, but it lives or dies on the skill of the people applying it. The method is a 5 to 7 cm layer sprayed over the existing tiles, followed by a protective coat of waterproof or elastomeric paint.<\/p>\n

    Spray-applied rubber<\/u>: highly insulating, waterproof, and it resists mould. It can be used on any type of roof and bonds well to the surface, so the work is clean and there is next to no waste to take away.<\/p>\n

    Why insulate from the outside<\/h3>\n

    Going in from above is more work, and it comes with paperwork. It normally needs a works licence from the town hall (licencia de obras<\/em>), plus a separate permit if the scaffolding stands on the pavement \u2014 worth knowing if you are new to the Spanish system. Our note on what kind of home improvements require permits<\/a> covers where that line tends to fall. What you get in return is worth the trouble:<\/p>\n