Obviously, accurate measurements of the existing building are important but attention must be paid to the construction of walls, floor and roof. If drawings and specifications do not exist for the property to be converted then the task of recreating these must be faced, including establishing foundation location, size and depth.
It is worthwhile examining what exactly is desired of the conversion; for instance, if it is intended to create storage only rather than habitable accommodation then the loading on the floor below and consequently on the structure below that, may well be significantly different.
The aspects to be carefully considered are as follows:
(1) The additional load of the new floors;
(2) The additional load of new walls;
(3) The additional load of ceilings;
(4) The additional live load of the occupants and the fittings;
(5) In the case of a third floor, the additional weight of fire protection to walls around stairwell;
(6) In the case of the creation of flats, the additional weight of the fire-resisting floor;
(7) If the conversion is to be used as a home-based office, the additional weight of office equipment and storage of files.
Any loft conversion which includes habitable accommodation is likely to add around 30% to the existing foundation loading, much of this being transferred to the foundations via lintels over windows and doors which will probably only have been calculated to carry a conventional load from the roof. Consequently, any conversion will have a significant effect on the structure below and as most bungalows have the same external load bearing wall construction as a two storey house, there is unlikely to be a problem with the wall itself; attention will have to be paid, however, to such items as the lintels, as explained above.
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