There is a significant difference between brickwork that gets wet and then dries off, and brickwork that stays saturated for hours, or that is allowing moisture through to the internal face. This page explains how to tell the difference, what causes excessive absorption, and what - if anything - needs to be done about it.
When wet brickwork is normal
Fresh or light rain will wet brick surfaces and make them look darker. On a reasonable day, most brick walls will dry back to their original colour within a few hours of rain stopping. This is normal behaviour and is not cause for concern.
When brickwork is absorbing too much water
There are three clear indicators that absorption has become a problem:
- The wall stays dark for many hours after rain stops. If a wall that faced rain at 9am is still visibly wet at 3pm on a dry afternoon, the brick is retaining water rather than shedding it.
- Internal damp appears after or during heavy rain. Damp patches on internal walls that correlate with rainfall - particularly on exposed elevations - indicate that water is travelling through the wall.
- Efflorescence appears repeatedly. White powdery deposits on the brick face are salts drawn out by moisture cycling through the masonry. Occasional efflorescence on new brickwork is normal. Persistent efflorescence on an older property indicates repeated, heavy saturation.
What causes excessive water absorption
Porous or weathered brick
Not all brick is equally resistant to water absorption. Older soft-fired brick, common in Victorian and Edwardian properties across Bradford and Leeds, can be quite porous. Prolonged weather exposure, acid rain, and freeze-thaw cycling all increase surface porosity over time. Some brick simply absorbs more than modern engineering brick would.
Failed mortar joints
When mortar joints have eroded or cracked, water doesn't just soak into the brick - it enters directly through the joints and travels laterally within the wall. This is often misidentified as a brick porosity problem when the joints are actually the primary route of entry. Repointing should always be addressed before any surface treatment is applied.
No original damp-proof course or cavity tray
On older properties - particularly solid-wall construction - there may be no cavity to interrupt water transfer from the outer to inner leaf. On some properties with cavities but older construction, cavity trays above lintels may be absent or failed. These are structural considerations that affect what remediation is possible.
Exposed elevation and elevation height
West and south-facing elevations on elevated properties receive far more wind-driven rain than sheltered aspects. Properties in areas like Ilkley, upper Harrogate, and the hills around Skipton can experience horizontal rain that places far more water on the wall than a sheltered urban property would see. This doesn't mean something is wrong - but it does mean the masonry needs to be in good condition to cope.
What a breathable water-repellent treatment does - and what it doesn't do
A breathable masonry water-repellent (sometimes called a silane or siloxane treatment) penetrates into the surface of the brick and reduces water absorption without sealing the surface. Critically, it remains vapour-permeable - moisture within the wall can still escape as vapour, so the wall continues to breathe. Non-breathable waterproof coatings or masonry paints trap moisture and are not appropriate for most brick walls.
What it does : Reduces surface water absorption significantly. Helps prevent frost damage to the masonry surface. Reduces the rate at which water enters during rain.
What it doesn't do : It will not fix failed mortar joints. It will not stop water entering through open or cracked pointing. It will not resolve existing internal damp - it can only limit future ingress after the wall is dry.
The correct sequence is : repair any failed pointing first, allow the wall to dry, then apply a breathable treatment if continued protection is required. Applying a water-repellent to a wall with open joints simply coats the brick around the gaps - the joints themselves will continue to let water in.
See our breathable water-repellent treatment service and cement and lime repointing services for more detail on both approaches.
What we assess before recommending treatment
Before recommending any surface treatment, we look at: the condition of the pointing, the age and type of brick, which elevations are most affected, whether there is evidence of existing internal damp, and what has been applied to the wall previously. Treatment applied over old coatings can delaminate, and some older coatings need to be removed before any new treatment will bond.
If water saturation is significant and there's existing internal damp, a Building Leak & Damp Inspection is the right starting point.