Foundation, Foundation Walls and Surface Bed
A competent person classifies the site in accordance with the site class designation set out in table 3 of the SAIEG publication.
Guidelines for urban engineering geological investigations.
Two types of foundations are used on non-problematic ground conditions:
cast in situ concrete strip footings may be plain or reinforced concrete (with a minimum compressive strength of 15MPa at 28 days).
Slab foundations with thickened edge beams and thickened surface bed under internal structural walls are cast integrally with a ground floor slab (typically 75 mm thick). They may be of plain concrete or reinforced concrete (with a minimum compressive strength of 15 MPa at 28 days).
The ground floor slabs are of cast in situ concrete, either power-floated to a smooth finish or with a sand/cement screed finish. The thickness of the slabs and the reinforcement, if any, depending on ground conditions, the building foundation with thickened edge beam to slab load and type of foundation used.
The floor slabs may be reinforced and thickened locally under loadbearing walls to bear the weight of internal walls, where no footing is provided for these. Foundation walls are built of 230 mm (nominal) thick brickwork.
Wall Anchorage and Damp-Proof Membrane
The figures illustrate the method of fixing Kwikframe panels to the 80 mm wide (depending on wall type) x50 mm deep recess formed in the perimeter of the concrete foundation/floor slab for external walls and thickened floor slab under internal structural walls (page 14 of the agrément certificate. An underfloor damp-proof membrane is provided in each case.
External wall panels are anchored to the perimeter beam with R8 mild steel l shaped anchor bars cast into the concrete at 600 mm centres (see page 13). The overall length of the bars is 900 mm, with the short leg of the L at least 150 mm long with the bar protruding at least 400 mm above the foundation/floor slab.
The R8 mild steel anchor bars can also be epoxied into holes drilled in the thickened perimeter beam at 600 mm centres. The anchor bars must be epoxied for at least 300mm into the perimeter beam and project at least 400 mm into the wall panel.
In both cases, the anchor bars must be coated with bituminous paint for 25 mm above and below where the bar projects through the concrete to prevent necking corrosion.
A thick bitumen layer (not less than 1 mm) is applied to the stepped concrete footing before the panels are placed and secured in position.
Internal walls serving a structural function (e.g. providing lateral stability to external walls) are anchored to the thickened surface bed with R8 mild steel L shaped anchor bars cast into the concrete. Two R8 bars are provided per panel, each bar having a minimum overall length of 600 mm, with the short leg being 150 mm long and the length of the bar above the surface bed at least 300 mm. The bars are epoxy coated 25 mm above and 25 mm into the concrete.
Non-structural internal wall panels are fixed to the concrete floor slab with a metal clip fixed to the slab with a Hilti nail. Galvanised steel wire ties run under this clip and are fixed to the wire mesh on either side of the KWIKFRAME panel. At least two clips are provided for each panel.