Tuesday, July 24, 2012

Is your loft suitable for conversion?

Conversion Assessment: The features that will decide the suitability of the roof space for conversion are the available head height, the pitch and the type of structure, as well as any obstacles such as water tanks or chimney stacks. An inspection of the roof space will reveal its structure and physical dimensions.
  

Head Height:
Take a measurement from the bottom of the ridge timber to the top of the ceiling joist; the useable part of the roof should be greater than 2.2m.

Pitch Angle: The higher the pitch angle, the higher the central head height is likely to be, and if dormers are used or the roof is redesigned, then the floor area can be increased.

Type of Structure: Two main structures are used for roof construction — namely traditional framed type and truss section type. The traditional framed type is typically found in pre-1960s houses where the rafters and ceiling joists, together with supporting timbers, are cut to size on site and assembled.

This type of structure has more structural input, so is often the most suitable type for conversion. The space can be easily, and relatively inexpensively, opened up by strengthening the rafters and adding supports as specified by a structural engineer. Post 1960s, the most popular form of construction used factory-made truss roof sections. These utilise thinner – and therefore cheaper timbers – but have structural integrity by the addition of braced diagonal timbers.   It is advisable to seek advice from a structural specialist in coordination with your architectural designer in this instance.

Low head height?
If the initial roof space inspection reveals a head height of less than 2.2m, there are two available – but costly – solutions that will require professional input.

Solution 1: Raise the Roof: Involves removing part or whole of the existing roof, and rebuilding to give the required height and structure. This is structurally feasible, but often costly. If the whole roof area needs removing, a covered scaffold structure, to protect the house from the weather during the works, would also be required.
Solution 2: Lower the Ceiling in the Room Below: The ceiling height in some rooms in older properties may be 3m or more, so if the roof space height is limited there is the option of lowering the ceilings below, providing it still allows at least 2.4m. This will require all the existing ceilings in question to be removed.  This is a mess undertaking indeed. With this method a plate will need to be bolted to the wall using shield anchors or rawl bolts, for the new floor joists to hang from. There is also a need for a suitable tie between the roof structure and the dwarf wall formed, to prevent the roof spreading.

1 comment:

  1. Good quality loft conversions can be actually great for house improvement in the UK. It is also an option to moving house if you are searching for an extra space.

    Loft Conversion Ideas

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