Retrofit sun roof lantern

Hi. In order to introduce a decent size lantern to an existing roof will almost certainly require strengthening of the existing structure. This would involve augmenting or substituting the full span members forming the edge of the new light well, and fixing in two trimmers to pick up the existing trimmed joists. This would almost certainly need the entire ceiling to be removed and replaced. A kerb would then be formed above the deck line. The new external structures would then need to be covered using an appropriate technique. If the existing roof covering is any more than 10yrs old, the entire roof should really be treated to a new surface, felt, rubber, GRP, PVC, kemper etc. I would only consider keeping the existing roof in place if you’re proposing a very small lantern in a very big roof, with a fairly new covering, otherwise it would be more cost effective just to install a whole new roof and lantern.

Hi A roof lantern would certainly introduce light into the area. Adding weight to the existing roof would require the existing timbers to be doubled up around the opening to add strength to the roof to make it structurally safe. This would usually involve building regs, if the flatroof is old then I would advise to replace the flatroof with a newer product. GRP, Rubber or Armourplan. There are other profucts. If the property is situated within a conservation area then the outside would usually need to be dark in colour instead of white. We have fitted several lanterns over the past few years and I always advise the customer to have the conversation with planning and to have an email confirmation that Planning is not required, just in case something should flag up when selling or in the future. The building control may ask for added ventilation and insulation to bring the existing extension upto current standards. This does not have to be an expensive upgrade and always worth having the conversation before the works starts.