FLINT WALL BLOG

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Brick re-pointing

Depending on the building's status, flint work will be framed in masonry of one kind or another.

Vernacular buildings commonly display brick piers & quoins whereas more monumental architecture such as St. Michaels in Lewes may feature lime or sandstone ashlar. Most buildings of any age will be constructed using lime mortar & the mix of this mortar will often blend with that of the flint work. An absence of grit or aggregate greater than 3-4mm in the joints of the brickwork is normally all that differs from the mortar of the brick & that of the flint. At the Flintwall company we are often employed to re-point flint walls & the condition of the brick work is invariably consistent with that of the flint.

We therefore have gained extensive experience in re-pointing bricks with lime mortar over the years. Where necessary we can analyse the existing mortar so that we can design our new mortar to match in colour & performance. We are also proficient in the removal of cement as the first step to re-pointing in lime, this is a task that requires patience & diligence. Through the use of hand tools we can carefully break out the cement with minimal disruption to the arises of the brickwork. We shy away from the use of power tools such as angle grinders as we believe they cannot be controlled to the same degree a hammer & chisel can.

Before Brick wall before re-pointing After Brick wall after re-pointing

Mortar trends

Despite a current trend back towards the use of lime many people are still wary of it & opt for what is perceived as the safe option of using a cementitious mortar. This is invariably a poor choice for any historic building for a number of reasons, which would take pages to explain in full but we will spare you & give a brief case against the practise.

The golden rule is that the mortar should never be harder than the masonry it encases. The mortar should be designed to be sacrificial. Once applied the cement will harden to surpass that of most historic bricks, & with time a rounding of the brick arises will occur. Cementitious mortars do not allow moisture to pass through them. The fact that the mortar will not allow moisture in is part of their attraction, however historic buildings were designed to breathe & to cope with water ingress.

Sealing the wall with cement traps the moisture in & leads to internal failure of the mortar & ultimately to the detriment of the masonry. As the moisture within the wall cannot be released through the cement it tries to make its way through the next most permeable substance which will be the brick, this can lead to spalded brickwork where the face completely deteriorates to leave a crumbly hollow. This can sometimes be rectified by carefully extracting the brick, turning it round & setting it in a fresh mortar.

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