How to Repoint a Wall
To the novice, the prospect of repointing a wall may seem a bit daunting. But it can be done by taking the following steps.
First of all rake out the mortar joints to a depth approximately equal to twice the width. So if you are working on an average 10mm wide brickwork joint, then you should be raking out to approximately 20mm. The use of specifically designed tools (joint raker) for raking out avoids damage. Brush any loose pieces away.
Damp down the brickwork and the mortar joints, it is important that the mortar joints are damp rather than the surface of the wall being wet (we use plant sprayers). That may mean spraying it and letting it soak in for a few hours. If your wall is very dry it may be wise to spray it the day before as well. By doing this you prevent the mortar from drying too quickly, helping it to bond better and avoid cracking.
Knocking up your mortar. If you have got premixed coarse stuff from us then it is probably advisable to remove the small amount of excess water which may be on the top of the mortar and then tip it out onto a wooden board, (this allows any excess water that in the mortar to soak away). If you are using a shovel to knock up the mortar then you should use the back of the shovel to squash the mortar to plasticise it and make it workable. Lime mortar is a thixatropic material, this means that the more you work it, the more workable it becomes (i.e. softer and wetter). So even if it feels fairly dry and stiff to begin with, persevere and only when you find yourself getting really tired should you add a small amount of extra water. Remember that too much water in the mortar increases natural shrinkage and can lead to cracking.
Put a small amount of mortar on your hawk and using your trowel or pointing iron, work it down into a pattie approximately as tall as your mortar joints, chop the edge off the pattie with your trowel or pointing iron. The mortar should be of a consistency that 1½" or so will stand off your trowel fairly easily. Always try to work towards your previous (or original) mortar, pushing the mortar firmly in place. Use a narrow pointing iron and try to keep the mortar off the face of the bricks. Keep the work tidy but avoid scraping wet mortar across the face of the bricks, any overspill (or feathers) are best left until leathery hard. Avoid over-working the face of the mortar once it is in the wall as this may make it whiter, and weaker, than it otherwise would be.
After three or four hours or so (depending on weather/temperature) you should find that the face of the mortar is sufficiently stiff that you can not mark it with your thumb, but can with your nail. At this point take a piece of wood that has been cut off to an angle of approximately 45º and is approximately the same width as the joint. Run this piece of wood along the joint applying constant pressure. You will find that most of the feathers, which appeared earlier, will drop off. If you are working during the colder months of the year, it may now be necessary to cover the mortar with hessian (and maybe polythene). This is to prevent the mortar being damaged by frost attack. It is also advisable to cover mortar (with damp hessian) on hotter or windier days as these elements can dry mortar too quickly - leading to cracking and weak mortar.
Use a stiff brush (scrubbing or churn brush) to brush off the remaining feathers and then stipple/tamp the surface of the mortar joints to reveal some of the larger aggregate and simulate some early weathering.
Choose the right lime
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