We are extending our existing house and due to the slope at the back of the house and the height of our upstairs, we need to keep the pitch of the roof on the extension shallow. Our Architect has suggest a zinc roof but I wondered what other options we might have other than a flat roof.

  • Nigel Lewis

    Hello Yvonne,

    You didn’t clarify it but I think you are talking about a single storey extension where the height of the upstairs windows dictates the shape of the roof on the extension below. This is a common problem faced by everyone wanting to add a rear extension who does not want a flat roof.

    You don’t mention the angle of the roof or the size of the extension, but usually extensions can be built projecting out from the rear of the main two storey wall of the house by 2.7 – 3.0m with a shallow pitched roof with tiles. The deciding factor on the distance of the extension is either the use of material to weather proof the roof or the angle that Velux type windows can be used if these are required. Whilst some tiles can go down as low as 12.5 degrees, it is more often the desire to have roof windows that decide the angle of the roof. If the roof is to have Velux type windows the angle of the roof must be 15 degrees or more.

    Below the 12.5 degrees for tiles or 15 degrees for Velux roof windows, it would be necessary to consider a sheet material covering which I guess why your Architect has suggested Zinc. Copper could also be used, this would be more expensive than Zinc (which is already an expensive choice) but has a lovely colour tone and ageing patina. Copper would look more expensive than Zinc and less industrial, but it would not suit all properties or designs and is probably best suited to a traditional style. Zinc which can be used with a modern or traditional design can be used down to 3 degrees which would allow a much deeper extension to be added.

    Whilst the Zinc will take on a nice patina after a few years, it is unlikely with a very shallow roof that you would see the benefit of this from your garden unless you could stand a long way back. In my experience very shallow pitched roofs tend to have large areas of eaves whilst their low angle means that you do not get to see much of the beauty of the roof from ground level.

    If the roof is very low which means that the beauty may only be evident from the upstairs windows and not the garden, you might want to reconsider a flat roof or alternatively compromising on the distance that the extension projects in order to improve the aesthetics (angle) of the roof. In any case, you need to be comfortable that use of a different material on the extension is going to be appropriate for your house which probably has a different roof covering than is being proposed.

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