by Before any renovation work begins, checking the damp proof course is essential to protect the structure and interior finishes. A clear understanding of its condition helps avoid costly repairs later on. This guide explains what to look for and how to proceed safely.
Locate the Damp Proof Course
The damp proof course is usually found at the base of the walls, just above the foundation. It runs along the perimeter of the house and may be hidden behind plaster or timber framing. Finding it requires opening a section of wall or inspecting the base of a chimney or stairwell.
Look for a distinct change in material, often a metal or plastic strip. It may be marked by a different colour or a subtle seam in the wall surface. If the wall appears uneven or has a slight bulge, the course may be visible there.
Mark its position with a pencil or a small piece of tape for reference during inspection.
If the wall is finished, consider removing a small section to expose the underlying structure.
- Check for a visible strip of metal or plastic.
- Look for a change in wall material.
- Mark the location for future reference.
Inspect for Physical Damage
Examine the course for cracks, dents or missing sections. Cracks can allow moisture to seep through and cause mould growth inside the walls. Dents may indicate past impact or settling that could compromise its integrity.
Use a flashlight to spot any unevenness or gaps between the course and the surrounding wall material. If the course appears warped, it may have been exposed to prolonged dampness. Any loose or detached parts should be noted for repair or replacement.
Avoid touching the course with bare hands; use a glove to prevent contamination.
If you discover significant damage, consult a professional before proceeding with renovation.
- Check for cracks and dents.
- Spot gaps or unevenness.
- Note any loose sections.
Check for Moisture Signs
Moisture may appear as a damp patch on the wall surface or a faint sheen on the floor below. Look for any damp spots near the base of the wall or around windows and doors. A persistent damp smell can indicate hidden moisture behind the wall.
Use a moisture meter if available, or simply press a damp cloth against the wall; a wet feel may reveal hidden dampness.
If moisture is present, assess whether it is coming through the floor or the wall itself.
Dry the area thoroughly and allow it to air out before continuing with any work.
- Look for damp patches.
- Check for a damp smell.
- Use a cloth to test moisture.
Assess the Course’s Sealant
Many courses are sealed with a waterproof tape or paint to prevent water ingress. Inspect the sealant for cracks, peeling or missing sections. A broken seal can allow rainwater to penetrate the wall cavity.
If the sealant appears damaged, apply a fresh coat of waterproofing compound after cleaning the surface.
Ensure the compound is compatible with the existing material to avoid future peeling.
If you are unsure about the right product, seek advice from a qualified tradesperson.
- Check for cracks in the sealant.
- Look for peeling or missing areas.
- Apply fresh waterproofing if needed.
Verify the Course’s Height
The damp proof course should extend a sufficient distance above the ground to stay dry during rain. Measure the height from the ground to the top of the course using a tape measure.
If the course sits too close to the ground, it may be vulnerable to surface water.
Consider installing a small drainage strip or slope to divert rainwater away from the base.
Any modification to the height should be carried out by a professional to maintain structural integrity.
- Measure height from ground.
- Check for proximity to ground level.
- Add drainage if necessary.
Look for Structural Support Issues
The course often sits on a concrete slab or a timber footing; both need to be sound.
Inspect the slab for cracks, damp patches or shifting.
If the footing shows signs of rot or decay, it may compromise the course’s effectiveness.
Repair or replace any damaged structural elements before proceeding with renovation.
- Check the concrete slab for cracks.
- Inspect timber footing for rot.
- Repair any damaged supports.
Plan for Safe Removal
When cutting into the wall to access the course, use a saw with a fine blade to minimise damage.
Wear protective eyewear and a dust mask to avoid inhaling particles.
Keep the area well ventilated and clear of flammable materials.
If the wall contains electrical wiring, switch off the power at the nearest circuit before working.
- Use a fine-bladed saw.
- Wear protective gear.
- Ventilate the area.
- Switch off power if necessary.
Ensuring the damp proof course is intact and dry protects the house from future damp problems and mould growth. Follow these steps carefully and seek professional help if any part of the process feels beyond your comfort level.
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