An established construction company specialising in the restoration and extension of period properties and listed buildings.

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Cement pointing

Can cement pointing be used on my older building?

Cement cannot and should not be used for pointing on an older building as it is non-permeable i.e. it seals up the pointing area making the bricks and/or stones the more permeable part of the outside of the building. This leads to a more accelerated rate of erosion than would occur naturally over a longer period of time.

Cement provides a seal that excludes moisture as opposed to lime mortar which is permeable and allows the building to breathe. Bricks and/or stones around an area of cement pointing are more vulnerable to decay such as salt action or frost penetration. Lime mortar also offers flexibility of movement within a building as opposed to a cement mortar which is rigid and can trap water. If the building is affected by shrinkage or minor movement, lime mortar will accommodate that movement whereas cement will tend to crack.

How can I differentiate between cement pointing and traditional lime pointing?

Lime mortar used for pointing, has distinct characteristics that can be identified as being very different from a cement mortar.

Lime mortar has an open texture and is light in colour as opposed to the hard, dull, grey mortar mixed with Portland cement, which is not compatible with bricks or stones and does not ‘blend’ into the building. A cement mortar will also decay differently from a lime mortar. It will crack, drop out in small sections or even stand proud of decayed brick or stone, whereas a lime mortar will gradually decay with the process of erosion.

The style of pointing finish is also a fair indicator as to the mortar that has been used. Cement mortar styles include concave or bucket handle, a protruding or ribbon finish or an angled or feathered finish.

My pre-1800 property has inappropriate cement pointing. Should I have it all removed?

Ideally, you should consider having the cement pointing removed but it is quite probable that this will cause further damage to the fabric of the building. We would recommend instead a more pragmatic approach such as the removal of a small section of decay as a trial area to be observed or even the patch pointing of localised areas of decay. Alternatively, you could wait for the cement mortar to fall out of the decaying areas.

A contractor suggested using power tools to remove the cement pointing. Is that the best method?

If not used correctly by a highly trained operative, power tools can cause a great deal of damage to the bricks and stones. It may be possible to cut out the mortar with hand tools such as a chisel, light club hammer or quirk. Bolsters or hammers are not recommended. It may also be possible to remove fine joints by using a handsaw.

I was told that a lime and cement modified mix could be used for re-pointing. Is that correct?

Recently cement has been added to modify some lime mortars, but this is not favourable as a greater variety of lime has now become available. Ideally a lime mortar that matches the colour, texture and profile of any existing lime mortar should be used, as it is sympathetic to the existing mortar and will blend into the fabric of the building.

If there is no existing lime mortar, a suitable lime mortar blend will need to be designed so that it is weaker than the existing bricks or stones. You should also consider the exposure to which the lime mortar will be subjected.

You should always use a skilled contractor who is familiar with lime-based materials, their mixture, usage and application.

At Heritage Restoration we can offer expert advice on all aspects of re-pointing and maintenance of period properties. Please contact us.

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