Lime or chaux in building
Lime comes in various categories and types. Not all are commonly used in the DIY environment.
The lime used by ‘amateurs’ is the lime called (in France) ‘chaux aérienne eteinte pour le batiment’ (CAEB). It is prepared from very pure limestone, and is an extremely fine powder. It is sometimes also known as ‘fleur de chaux’.
‘Chaux hydraulique naturelle’ is also sometimes used, but is less pure and has a slight grey tint.
Stand well back after emptying lime into a cement mixer. It tends to come back out in a fine cloud, coating you head to foot ‘Laurel and Hardy’ style, and making you choke at the same time.
Uses
Visit the walls page for a list of the diferences between cement and lime when used for pointing and stonework. Suffice to say here, lime has numerous advantages during the renovation of an old building, and few disadvantages. The only general disadvantage of lime is that its ultimate strength is less than that od cement, so would not usually be used for bricklaying, for example, and would never be used in lintels or in other work with a ’structural’ factor.
It can (and should) be used in place of cement for rendering walls and pointing walls, although a small amount of white cement can be added to give extra strength.
April 28th, 2007 at 8:30 am
i have tried to crepi a large wall but you can see all the joins where i stopped and started how do i get rid of these lines after it has dried. there is also a large patch which looks a very different colour why is this? please help if you know how i can fix this on my house.
many thanks
April 28th, 2007 at 9:36 am
Hi Lisa,
Sorry to say but I think there is no way to correct it! Applying large areas of lime based crepi is quite a tricky job, because the moisture and air temperature are critical and it is these that cause the problems.
A professional will apply a rough undercoat first, allow it to dry, and then apply the final coat. (sometimes three coats are used). The different layers are often applied by a machine so that large areas can be done quickly.
The role of the first coat is, in part, to ensure that the second coat is an even thickness and hence dries at a constant rate.
The warmer the air when the crepi is applied, the faster it dries, and the faster it dries the more the lime is carried to the surface. So crepi applied on a warm day will be lighter than crepi applied on a cool day. Similarly, the moisture content of each batch of crepi applied must be identical.
Joins being visible is, I think, for the same reason - the edges dry at a different rate. Although in any case it is very hard to hide the joins - so really a whole wall needs to be completed in one ’sitting’.
On walls I have done (never especially large, and only on outbuildings, not important walls) I have also managed to reduce the problem by gently brushing the wall as it dries, including the join. This works reasonably well, but again depends on doing the whole wall in one day.
Another option is to use a ‘wire stippling brush’ (like the macons use)on the wall as it dries - these are available in DIY shops and make the surface evenly ‘rough’, and would reduce the visibility of the joins.
But as for correcting an existing dry crepi wall? I’m afraid I don’t have any great suggestions, sorry!