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Sectional garage doors are best fitted to the back of the structural opening but can be fitted inbetween the opening if required.
All sectional type garage doors were originally designed to be installed behind a structural opening with the running tracks at the side going up the inside of the piers and the spring mechanisms always behind the lintel or the back of the piers too. Over the last few years manufacturers have developed various brackets and finishing/cloaking accessories to enable the installation of a sectional door in between the structural opening if required. You have various considerations to make when doing this unless other factors determine that you have to fit in between, such as the absence of an internal face or any headroom at all.
For most manufacturers a sectional garage door has a steel L shaped frame leg either side of the main door opening and this is usually about 85-90mm wide either side. This frame is normally pre drilled for installation direct to the inside face of the brickwork opening and the ordering size is the width between these frame legs. The height required above a sectional door for installation depends on the width as different manufacturers put the springs in different places but generally you will have a minimum requirement of 115mm and a maximum of 225mm BUT a big factor will be where the lifting springs are situated. If, for example you order a double width Hormann or Garador then a 'torsion' spring will be supplied to fit above the top door panel with a minimum headroom requirement of 210mm but it will also need several secure fixing points for the spring support brackets and if you are installing inbetween an opening the chances are you are also underneath the RSJ/lintel and this could mean you only have fresh air to fit into! If the door is a single width then the springs are situated down the sides and the headroom requirement is only 115mm with no requirements for fixing apart from securing a 95mm fascia section supplied but this is relatively easy to do with some steel brackets.
Carteck sectional doors always have their springs situated in steel channels above the tracks and for most widths only require headroom of 120mm making the Carteck ideal for garage openings with limited headroom or where you have to fit inbetween the opening, especially if it is a larger double width door size.