Roundtower Lime A Guide To Internal Lime Plastering | Page 3

which will result and a weak and powdery may need to be carried out the previous
interface which will lead to later failure and day or several times throughout the day
separation. Where there is little or no before rendering commences.
suction further action will be required to The objective of the suction control is to
help bond the coating to the substrate. In achieve a thoroughly damp surface, but
situations where suction needs to be not wet, i.e., the surface must not have
controlled, wetting down will be required, running or standing water remaining on
on dense blocks or near impervious the masonry or brick, this will form a
masonry, simply dampening the surface barrier between the coating and substrate,
with a mist spray may be all that is also lime mortars adhere and stiffen
required, but on very porous surfaces such through a certain amount of suction.On
as old brickwork considerable wetting will dense or near impervious background, it
be required. Wetting the wall by use of a may be necessary to apply a
hose, working from the top of the structure, sand/splatterdash coat to the background
downwards, to act as a mechanical key.
SALT CONTAMINATION
Where new lime coatings are to be applied Salt contaminates should never be washed
to masonry which is salt contaminated, the from the surface, as this will result in the
masonry should be allowed to dry fully crystallized salt returning to a soluble state
before applying new renders. This will and retreating back into the pores of the
allow salt to be detected on the masonry masonry or brick. Where detected on the
and mortar joint surfaces, if excessive salt is masonry surface, the salts should be
identified clay or lime mortar poulticing brushed from the surface and cleaned
may be required. Specialist advice should away from the structure.
be sought, if the technique is considered
where salt is detected on the mortar joints,
rake out the joints to a depth of 50mm, as
this is likely to be heavily contaminated
and in a weakened condition and repoint.