Brick Cleaning Cardiff

Why sandblasting ruins brickwork

A brick is fired hardest at the surface. That outer few millimetres is denser than the core and it is what keeps water out of the wall. Sandblasting, and high pressure held close, cuts straight through it and exposes the soft body underneath. The wall looks clean for a season and then holds water, grows algae faster than it did before, and starts shedding face in frost.

It is not a reversible mistake. Once the skin is gone the only fixes are a breathable masonry coating or a re-face, and both cost many times what the clean did.

What is actually on your brickwork

Most Cardiff brickwork is carrying one of four things, and they need different answers:

• Green algae and mould, which is a biocide problem rather than a pressure problem. It comes off at very low pressure once it has been killed.
• Black soot and traffic film, common on older terraces near main roads. This is ingrained and needs a chemistry that lifts carbon, not more force.
• White efflorescence, the powdery salt bloom. Washing it makes it worse. See our efflorescence page.
• Mortar smears and cement splashes from building work, which need a controlled acid and a spot test first, because acid burns some brick colours.

The method we use on brick

We start at the lowest pressure that will do anything and only go up if we have to. In practice most brick cleaning is a soft wash: wet the wall, apply the right product, let it dwell, then rinse at a pressure closer to a garden hose than a lance. Where a job genuinely needs more, hot water at low pressure does more than cold water at high pressure and does it without cutting.

Mortar and cement removal is the one case that needs acid, and it always gets a test patch somewhere inconspicuous first. Some yellow and buff bricks stain permanently on contact with the wrong strength, and there is no way to tell from the surface which ones will.

New brickwork is a special case

If your brickwork is less than about a year old, leave it. New walls push construction salts out for months and cleaning them early just brings more through. If the builder has left mortar smears that have to come off, that is a different job from cleaning, and it is worth doing before the smears carbonate hard.

Pointing decides whether we can clean at all

Soft or missing mortar joints are the reason we sometimes say no. Water at any pressure goes where the mortar is not, and on an older Cardiff terrace with lime pointing that means straight into the cavity or the room behind. We check the joints before quoting, and if the pointing needs work first we will say so rather than wash it out and hand you a damp problem.

What changes the price of brick cleaning

A single elevation on a typical semi is usually a half day. A full house exterior is a day, sometimes two if there is heavy soot or the access is awkward. Mortar smear removal is priced separately because it is slower and needs the test work first. Every price is fixed before we start, and if we find soft pointing at the survey we tell you then, not halfway through.