Garage wall weather resistance and DPC

150 mm

Every figure for this topic is on one page: Cavity trays and DPC: where are they needed and how high?

Garage walls must effectively resist the penetration of rain and groundwater. A damp-proof course (DPC) must be installed at least 150mm above adjacent ground level to prevent rising damp. Single-leaf masonry walls, especially in exposed locations, may require additional measures such as surface treatment or a cavity construction to ensure adequate weatherproofing.

Basis in regulation

Part C
Approved Document C
Read the source

How to check it on site

Verify the DPC is at least 150mm above ground and that external walls provide sufficient resistance to rain penetration appropriate to the exposure conditions.

Common failure

Inadequate DPC height or lack of appropriate weather protection for single-leaf walls can lead to dampness within the garage.

Last updated 2 September 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.

Related dimensions at this stage

Maximum

Wall tie spacing at reveals and movement joints

Additional ties at 300 mm vertical centres within 225 mm of the opening

Within 225 mm of an unbonded vertical edge — reveals, movement joints, wall ends

Maximum

Cavity wall tie vertical spacing

450 mm

vertical spacing of cavity wall ties does not exceed 450mm.

Maximum

Cavity wall tie horizontal spacing (partial-fill insulation)

600 mm

horizontal tie spacing for partial-fill insulated cavities does not exceed 600mm.

Maximum

Cavity wall tie horizontal spacing (full-fill insulation)

900 mm

For cavity walls incorporating full-fill insulation, wall ties must be placed at maximum 900mm horizontal centres

Maximum

Lowest fixing position for straps

150 mm

For any structural strap, the lowest fixing into the masonry or supporting structure must be positioned no more than 150mm from the bottom of the strap

Minimum

Chimney wall thickness and construction

100 mm

The minimum wall thickness for block, brick, or stone chimneys, excluding flue lining, is typically 100mm