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Timber Frame Construction



Platform floors

Platform floors are the most common type of intermediate floor construction used in timber frame construction. Platform flooring involves the floor joists resting on the ground floor wall frames, creating a platform of the first floor where the upper storey timber frame structure can be erected.

A range of joist may be used when constructing a platform floor; these include:

  • Conventional floor joists

  • Proprietary timber l-joists

  • Proprietary open steel web joists

Typically, the platform floor, regardless of joist type, is constructed at factory level to be installed on-site.


Floor decking is normally fitted at factory level before being brought to site. The floor decking is installed on top of joists and noggins that provide the support base; an expansion gap must be left around the perimeter for any movement that may occur (as determined at factory). Typical materials for floor decking include plywood, chipboard, floor boards, etc.

It is important that during transport and storage the floor decking is protected against damage and the weather in case distortion occurs to the material.


Panel construction, fixing, and packing

Platform floor panels are normally constructed off-site. Once on-site they can be installed by hoisting the panels into place. The panels are fixed to the top of ground floor timber frame panels below and any internal load-bearing walls. It is critical that the lower timber frame panels are level before installation of the floor panels. Differences in level will create an uneven floor level and may cause knock-on issues further into construction. If it is found that the lower timber frame panels are not level they may be packed to eliminate any differences in level.

Consideration must be taken when packing to ensure no gaps are created around external walls, breather membranes, party walls, fire barriers, etc. to ensure the seal and effectiveness is not compromised by the inclusion of packing material. Packing should not be vulnerable to shrinkage and should be of continuous installation in areas where required.

Installation, inspection, and fixing

Once the floor panel is installed, it is again inspected to ensure that the panel is level and that contact is distributed equally amongst the supporting members that support the load. Once installed, the floor panels become the base platform for which the next storey is constructed on. The wall panels from the next story are installed directly onto the floor panel.

Once the initial inspection of the floor panels is complete and once it is in place, the lower floor timber frame structures and load-bearing walls that support the upper floor panel are then to be inspected to ensure they have not moved or been damaged during the hoisting in of the floor panels above.

Once the floor panel is level and the load-bearing frame beneath is as before, the fixing can begin. The floor panels should be fixed to each of the external walls and each of the internal load-bearing walls that support the panel. It is also important to remember that the floor panels must be attached to each other adjoining panel also to increase rigidity.

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