Guide for installing insulation in a basement extension

Tips for insulating a new basement

• Kingspan GreenGuard boards can either be laid above or below the damp proof membrane (min 1200 gauge polyethene) above the compacted hardcore. If fitting the insulation above the DPM then a polythene sheet (min 500 gauge) should be overlaid on the insulation to prevent the wet concrete penetrating the insulation during pouring.
• The DPM should be laid under the basement walls and a triangular shaped piece of Kingspan GreenGuard placed between the slab and the exterior of the basement wall to create a slope and the platform for the basement wall.
• A 30 mm min strip of Kingspan GreenGuard should also be laid vertically as an upstand around the perimeter of the floor slab internally, running from the bottom of the floor insulation to the top of the floor screed.
• The wall insulation should be fitted externally of the tanking membrane which is applied to the external walls. 
• All insulation boards should be fitted break bonded with no gaps. If more than one layer is installed then joints should be offset. 
• A cavity drainage membrane or layer of no fines gravel should also be fitted outside the insulation board and should be covered with a geotextile membrane to prevent fines from blocking the drain. Additional ground drainage may also be needed depending on the ground conditions.

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