Tips and tricks for cleaning old French brickwork

Brickwork goes in fashions. One generation treats it as purely structural and wants to hide it behind paint or plaster; the next to show it off as a feature. 

I am firmly in the latter-day camp. Exposed brickwork, even if it was never intended by the original builders to be seen, can be a thing of wonder in an old property if it is treated properly. 

Only occasionally, if it has degenerated into a very bad condition, should it be covered up. What is certain is that you have to decide one thing or the other: if you are going to restore it to eminence you are going to have to invest time and effort. 

Read more: 'How we are reviving our Belle Epoque property on the edge of Lyon'

Before we go any further, I want to make two distinctions. 

One is between industrial bricks which were manufactured from the end of the 19th Century onwards, and their handmade equivalents which are generally much older. 

Mass-manufactured bricks are uniform in size, shape and colour; and they tend to be more resistant to the elements and therefore need less attention. 

Artisanal bricks (briques foraines), in contrast, are irregular and quirky in both dimension and tone of baked clay. Most of what I have to say is about the care of these charming pre-industrial bricks.

The other distinction is between exterior brickwork, exposed to uncountable winters of bad weather, and its interior counterpart, which will have suffered much less damage. 

I will deal with heavy-duty work on outside walls this time and get on to the finer points of cleaning up all brickwork – inside and out – in a follow-up article.

There is no point in cleaning bricks if they are not in a sound state. The first task therefore is a close inspection to see if structural repair is needed. This is for both aesthetic and practical reasons. There must be no cracks in brickwork where moisture can creep in and eat away at the wall from within. 

This means checking not only the bricks themselves but also the joints between them (vertical and horizontal). 

If any of the mortar is loose or crumbly it must be scraped out and replaced: a process known as repointing (rejointoyer in French), or tuckpointing if it is just in the odd place. 

Be sure to remove all loose particles, however deep they lie, before you start to refill. 

Ideally, you will match the new mortar to the old using either lime or a suitable sand – as I discussed a while ago. 

Repointing is not something to do in cold or freezing weather or the fresh infills may crack and let in moisture.

Next, the bricks themselves should be examined. It is not uncommon for the damp and cold to creep into individual bricks making them porous and soft. 

A repeated process of freezing and thawing causes the bricks to shatter or “spall”. Such bricks are unrepairable. You will need to remove them entirely with a hammer, chisel and drill if necessary, along with the old mortar that held them in place. 

The replacement of a spalled industrial brick is straightforward: one size fits all. For a handmade brick, you may have to fashion your own to fit, cutting a larger brick to shape with an angle grinder and masonry disk: as long as the outward face looks good, the roughness of the other three sides does not matter. 

Do the cutting as far away from civilisation as you can manage: red brick dust goes everywhere.

Once the brickwork and mortar joints are sound, the heaviest and messiest work is done and you can get on with the cleaning.