Custom Decorative Plasters

Technical specification

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Plaster and lime Coatings on wire-mesh supports

Plaster and lime Coatings on wire-mesh supports


1.1. Principle

System intended to carry out plaster-and-lime coatings on wire-mesh supports. The principal components are the Coating or the Mortar of Montmorency (mixture of plaster and lime, with or without sand, tinted in the bulk or not) and the wire-mesh.

1.2. Field of application

This system can be used in interior as in exterior, in compliance with the rules of protection of the Coating of Montmorency, recalled in chapter 2.3. This system cannot be regarded as sharing any effort of its support. Consequently, one will take care that the wire-mesh support is ready to support its own efforts and loads, like those generated by the system. In a more general way, in the case of a new support, it will have to be in conformity with the DTU corresponding. The Coating or the Mortar of Montmorency cannot be used with a final thickness lower than 25 mm/ 1 inch in exterior and 20 mm / ¾ inch in interior.

1.3. Constitution of the system

The Coatings and Mortars of Montmorency are a mixture of plaster and of lime, with adjuvants, with or without an aggregate load, tinted or not. By convention, in the continuation of these specifications, one will use the expression “Montmorency Coating ” instead of “Coating and Mortar of Montmorency”.

Specificity of the components:

coating and mortar of Montmorency: coatings of the company DécoSystème, defined by specification of conditions.

metal frameworks: in conformity with the regulations of the DTU 26.1, and in particular protected from corrosion in accordance with chapter 2.61 and dimensioned in accordance with chapter 9.


2.1. Choice of the coating of Montmorency and the framework to use

the Coating of Montmorency to be used will be selected in term of composition, of grain and color in accordance with its specifications, in particular in terms of color and grain. The framework will be selected in accordance with the DTU 26.1 chapter 9. The lattice/rib of framework will be dimensioned according to the loads and efforts to undertake.

In particular, the weight of the Coating of Montmorency is of 12,5 kg or 27.5 lbs/cm thickness maximum once dry and 18 kg or 39 lbs/cm thickness gorged with water (in particular at the time of the implementation), since the minimum thickness is 20 mm / ¾ inch in interior and 25 mm / 1 inch in exterior.

2.2. Installation of the framework

2.2.1 State zero

One calls “State zero” the state of the support obtained after preparation in accordance with the metal framework regulations. In particular, one will take care that the points of anchoring of the framework are able to sustain the loads and efforts, static and dynamic, of the coating. Moreover, it is advisable to observe the following precautions:

All supports: it is pointed out that the system made up of the metal framework and of the Coating of Montmorency cannot be considered as bearing any effort of its support. Consequently, one will take care that the support of the metal framework is ready to sustain its own efforts and loads, like those generated by the system. This point applies in particular on the one hand to the cases of independent structures, carried or suspended and on the other hand, on old supports which must be if necessary, treated and/or repaired, even reinforced, according to the code of practice.

New supports: elements made out of hydraulic materials, be they prefabricated, manufactured , run in place or masoned, must have undergone a 30 days wet cure. In the same way, possible mortars for roughcasting or for finishing containing hydraulic binders must have undergone a 30 days wet cure.

This provision applies in particular to walls made in concrete and run / formed on site, to walls in blocks to built with a binder or an adhesive containing a hydraulic binder (terra cotta, agglomerated cement, gas concrete, complex bearing blocks, etc…). Prefabricated elements made out of hydraulic materials (stringcourses, cornices, balusters, sills, supports,…) : they must have undergone a 30 days wet cure before being brought to be in relation to the Coating of Montmorency and that be by contact, streaming or capillarity.

Timber frame: suitable treatment bistre stains: apposition of a bituminized felt/ tar paper. Once this preparation carried out, an attentive examination of the support makes it possible to ensure that there is not any suspect trace without explanation : traces of bistres, formation of salpetre, crossing cracks , tarring, etc…

2.2.2 Realization of the metal framework

The framework is laid out according to the code of practice. In particular, one will folow the regulations of the DTU 26.1 chapter 9 , as well as the possible recommendations of the metal framework manufacturer. In particular, one will respect these precautions in the cases of: expansion joints and joints of fractionation

Singular points: butting against another wall (wall return, panel, change in bearing structure,…)

External fixings

2.3 Implementation of the Coating of Montmorency

The implementation must respect the specifications in use for the Coating of Montmorency. One specifies here, some of them.

2.3.1 Precautions

The Coating should not be used at a temperature lower than 41o F / 5° C, neither in full sun exposure or under the rain, nor on frozen support.

2.3.2 Mixing

The Coating of Montmorency implementation can be done, either: by hand, using a mixer: the mixing rate is then 50 to approximately 65% in water weight compared to the weight of the powder.
By spraying, with a machine adapted to this use: the mixing rate is then approximately 65% in water weight compared to the weight of the powder.
These rates are reduced in the case of a mortar of Montmorency. In any case, the mixing rate must obtain a paste holding charge some 1 1/4 to 1 5/8 inch / 3 to 4 cm thickness. Water used will be clean and free from matter suspension. No additive or addition, others that adapted pigments, will be added to the product or mixing water.
In all the cases, the mix will have to be perfectly homogeneous, without clods.

2.3.3 Coating

The Coating is implemented in a first prime coat entirely covering the lattice. It is finished by “combing”. Then it is complemented by a second coating. The total thickness of the layer could not be lower than 25 mm / 1 inch once the coating finished in exterior, and than 20 mm / ¾ inch in interior. The coating is drawn up with a straight edge, then tightened. One should not remix the coating when hardening has started.

2.3.4 completion

After setting, one re-cuts the Coating of Montmorency with a the sharp berthelet (or in the case of Mortar of Montmorency, one scrapes with a devil's float, a hawk with nails ). It can also be brushed or washed after setting (washing sponge or hard brush ). It will then be rinsed in a careful way with water slightly under pressure, in order to eliminate the laitance. In exterior, it cannot be smoothed-finished , nor burnished (except the case of specific bands: surounding frames, bandsof angles, platband between story levels). The fresh coating must be protected from the too violent direct radiation of sun. Moreover, it must remain moist at least a week. If necessary, it is appropriate of rehumidify the coating with clean water, by spraying. Conversely, it is advisable to prevent that the coating does not remain moist too a long time, whatever is the cause, so that its carbonation can be accomplished. When its hardness is sufficient, the coating can be re-cut, in particular for the scoring of joints. Once perfectly dry, the coating can also be sanded or renovated ( included by processes of the rubbing type) like a very tender stone. Of course, the constraint of the minimal thickness is to be respected in these work included (in the case of dug joined left hollow, the thickness is to be measured from the bottom of the joint; in the case of a scored joint filled in Coating of Montmorency, white or tinted, the thickness is measured from the surface of the coating).

2.4 Particular points of implementation

2.4.1 Before coating Change of bearing structure

A hollow joint will be realized between the parts of the different bearing structures (for example in the case of an elevation). In the same way, a hollow joint will be made right along possible expansion joints (for example, in the case of a new concrete contruction).

2.4.2 During coating External angles

The outgoing angles, for example at the level of the surrounds will be are carried out at once, or in two times. It is also possible to use angle rails. Angles of bays

One is reminded that the angles must realized by cutting in a plate and not by juxtaposition of 2 plates.

2.4.3 After coating Protection against localised streaming

In a general way, surfaces realized in Coating of Montmorency must be protected from any located streaming , in particular from water drops and back splashings. The following paragraphs treat of a few particular cases, but this principle of protection must be strictly followed in the construction of the whole and details of the work. In particular, as long as the Coating has not dried once and had time to carbonate, these precautions will be redoubled. horizontal Surfaces

Horizontal or quasi-horizontal surfaces more than 2 cm wide, realized in Coating of Montmorency will be obligatorily protected by a cover, for example a zinc coping. Horizontal or quasi-horizontal surfaces less than 2 cm wide, carried out in Coating of Montmorency will have obligatorily to present a glacis of more than 60° in slope (it is in particular the case with the tops of lintel mouldings ). Back splashing surfaces

Backsplash surfaces, i.e. located above a horizontal or quasi-horizontal surface of more than 2 cm of width, must be protected by a board/ band from backsplash at least 7 cm / 2 ¾ inch high. Windowsills

The preceding provision applies in particular to back splashing produced by the weathering on the window jambs. Moreover, the work will have to present so that the water collected by the support will be rejected on the front edge of the weathering support and not on the sides. In the case of zinc coping sills, an authorized solution consists in raising upwards the side edges of the sill protection. Wall base

The Coating of Montmorency could not be implemented at less than 40 cm / 16 inch. high from the ground. It is thus advisable to envisage a base at least this height. It will be with at the same facade level that the coating, or at least will present a glacis at more than 60°. Stringcourses and cornices

The distance between the check throat on the stringcourse and cornice undersides and the facade surface level of the coating must be 3 cm/ 1 3/8 inch per meter height before the following string belt, the coating surface level being considered just above this last stringcourse. Thus, in the example of one stringcourse per level, the width of the stringcourse between the level N and the level n+1, must be 3 cm /1 3/8 inch by meter height of level N plus the slope of level N. Gable walls

Only in the particular case of perfectly vertical non-bearing and blind walls, without cornice (crown mouldings ), is it not necessary to envisage a stepping of the facade by band courses, given that the edge be seamless and redirects all of the rainwater it collects back towards the roof (for example with splayed copings). Precautions during the construction progress on the building site

All the necessary measures will be taken to avoid the localised streamings related to the temporary conditions during building construction: back splashings on scaffold boards, interrupted rain water descents, absence or faulty functionning of the roof top works or belt course (one will take care in this respect of a good managing schedule for the construction on site), delays before the installation of zinc works, etc… In this respect, a careful covering is generally necessary.

2.5 Subsequent treatments

Any subsequent treatment others than those purely physical (sanding, joint scoring, re-cut,…) on the Montmorency Coating once finished, comes under the exclusive responsibility of the applicator and/or the supplier for treatment. The latter must bring their guarantee as for the behaviour, the harmlessness and the durability of their treatment on the Montmorency Coating and/or the elements of structure and/or salubrity of the work. These restrictions apply in particular to paints, waterproofings, etc… which, for lack of a specific study and of an explicit guarantee on behalf of the manufacturer and applicator, are formally prohibited.

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