2.1. Selection of the coating of Montmorency to be used
The first choice relates to the proportion of plaster and lime. By default, the proportion of lime, compared to the mix lime and plaster, will be 10 to 15%. According to analyses made in our facility, and to countertype an already existing coating, it is possible to vary the proportion of lime, provided that the latter remains ranging between 5% and 40%, in weight. In addition, one will choose the pigment and the loads necessary to obtain the color and the desired grain. This choice must be validated by the building owner or his representative.
2.2.2 Preliminary works
2.2.1 The zero state
One calls “ Zero state” the state of the support obtained after the following works:
The support must be purged of all its unhealthy or “loose” parts. In general, it must also be cleaned of any possible layer (for example paint, stains or finishing mortar), by scraping or scouring. Moreover, it is advisable to observe particular precautions in the following cases:
Old coatings: purge all the surface of the current coatings and the totality of non-adherent parts in order to leave a coat thickness of at least 1 inch/25 mm. Usually in fact, one pickaxes on the totality of the coat thickness until the support is reached. The remaining parts must be healthy, adherent and dust-free.
Joints: purge the totality of non-adherent joints (but one leaves those which are healthy). In this case, the minimal digging depth is then of 3/8 inch / 1 cm. Moreover, it is advisable to purge all non-conform joints (in particular joints made in hydraulic products: cement, hydraulic lime,…).
Stringcourse and cornice:
at least, purging of the parts in bad condition or loose. Brand new supports: elements made out of hydraulic materials, whether they are prefabricated or built, must have undergone a wet cure for 30 days . In the same way, the possible mortars for rough-casting or finishing containing hydraulic binders must have undergone a 30 days wet cure. This provision applies in particular to concrete walls poured on site, to walls in blocks to be built with a binder or a glue containing a hydraulic binder (terra cotta, cement agglomerate , gas concrete, composite bearing blocks, etc…).
Prefabricated elements made out of hydraulic materials (stringcourses, cornices, balusters, supports,…) : they must have undergone for 30 days a wet cure before being brought to be in relation to the Coating of Montmorency and that being by contact, streaming or capillarity. Once this preparation carried out, an attentive examination of the support makes it possible to check that there is not any suspect traces without explanation: traces of bistres, saltpeter (potassium nitrate) resurgence, transversal cracks, tarring, etc…
Particular case of the coating between the timbers :
Purge totality of the current coatings while avoiding damaging the skip sheathings. Inspection and purging of the existing skip sheathings: removal and possible replacement; at least, brushing and fungicidal treatment.
Particular case of buttering and coating for stones with heads visible :
It is advisable to check that the material composing the wall (generally stone or brick) can be left without protection, in particular from the point of view of its porosity, its mechanical performances and its gelidity. This point must be studied particularly in the case of a stone or of a brick coated before the work. In like manner, pieces of wood thus discovered must be suited to this use. the possibly existing coating is entirely pickaxed. The joints are purged on at least 1 inch / 25 mm in the case of a coating on stones with heads visible, and purged on at least 13/ 8 inch /30 mm in the case of a buttering.
2.2.2 Preparation of the supports
Mending of wire-meshes and rejointing of the supports if necessary: one uses the same technique and same materials than that pertaining to the wall. The state to be obtained obeys the same rules as “state zero”.
Stone: if surface of insufficient quality (crumbling,…), and only in this case, consolidation with PétraMinéral. It is then necessary to let solvents evaporate at least a week (more in winter) before covering this stone.
Brick: if surface of insufficient quality (powdering,…), and only in this case, consolidation with PétraMinéral. It is then necessary to let solvents evaporate at least for a week (more in winter) before covering this brick.
Gas concrete: abundantly wet the support.
Irons / metals: proceed with a scouring and passivate. Stuffing with plaster lime. Setting out of galvanized wire-lath.
Wood: carry out an inspection and a purge: any beam presenting a deterioration will have to be uncovered on all the affected zone at least 1 ½ foot / 20 cm on both sides; in the case of discovery of a cubic or fibrous rot, warn the project architect / foreman, in writing, of the possibility of a later recontamination by the mérule mushroom (serpula lacrymans; schum); removal and possible replacement; at least, brushing and fungicidal treatment. For this treatment, it is then necessary to let solvents evaporate at least for a week (more in winter) before covering it. One fills in PG, MG or PGA. One poses a galvanized wire-lath (coop, square wire-mesh or metal expanded without kraft paper) with galva points (alternatively one can lard the wood of large nails), then one then applies a coating of PG 15, PG 30, PG 100 or Coating of Montmorency (and not of standard coarse plaster) mixed tight (with little water) on the wood, on a thickness of at least 3/8 inch / 1 cm. It is excluded to put a bituminized felt or of any other processes prohibiting the drainage of water possibly present at the level of the wood frame.
Bistre stains: installation of a bituminized felt (no glass cloth), then a wire-mesh.
Form-panelled, smooth blocks or cast concrete:
a scratch coat as described in DTU 26.1 is applied (cement/sand scratch coat with rough finish). The hardening dealy is minimum 28 days (for complet cement setting).
Heterogeneities of the support: installation of a galvanized wire-mesh ( galvanized points), with a 6 inch /15 cm overlap on both sides of the changing material. On the other hand, one should never bridge an expansion joint. In the event of setting a wire-mesh all over, the overlapping of the wire-mesh edges is then 6 inch/15 cm.
Particular case of coating between timber frame:
Timber structure: repair or eventually replacement; strict minimum, brushing and fungicidal treatment.
Reconstitution of the skip sheathing (same position that originally, 1 to 1 1/4 inch / 2.5 to 3 cm behind the surface level of the facade, either out of wood with slats, or with a light metal structure of expanded metal type (stainless or galva including fixtures).
Particular case of the buttering and coating stones with tops remaining visible:
repair or possible replacement; as a minimum, brushing and fungicidal treatment.
Irons/ metals: proceed with a scouring and passivate.
Mending of the support meshes if necessary: one uses the same technique and same materials than that pertaining to the wall. The state to be obtained obeys the same rules as “state zero”.
Stone or brick: if surface is of insufficient quality (crumbling,…), buttering stones with heads remaining visible is proscribed, and a coating is to be envisaged (in this case, cf supra).
If the coat thickness to be applied is higher than 1 3/ 8 inch / 3,5 cm, and only in this case, it is possible to carry out a rough-floating. One will use obligatorily the following products, on a minimal thickness of 3/8 inch / 1 cm:
Manual rough-trimming: PG 15, PG 30 or PG 50 ( rough-trimming plaster of the DécoSystème company).
Spraying machine rough-trimming : PG 100 ( roughing plaster of the DécoSystème company) or in Coating of Montmorency.
In all cases, the trimming will be cut with a sharp berthelet (scraped only in the case of a Mortar of Montmorency trimming or with a MG).
One recalls that it is possible to put up to 1 ¾ inch. / 4 cm thickness in the sole top coat in Coating of Montmorency. Thus, in the example of a 1 ¾ inch. / 4 cm thickness, it is possible to make, either: a trimming of 5/8 inch / 1.5 cm and a top coat of 1 in./ 2.5 cm or directly a top coat of 1 9/16 inch /4 cm.
Particular case of coating between timber frames:
Rough-trimming in Coating of Montmorency on a minimum thickness of 3/8 inch / 1 cm, while taking care to properly coat the skip sheathings.
The trimming will be cut with the berthelet (cutting side) , once setting completed. The thickness for the top coat must be at least 5/8 inch / 1,5 cm.
2.3 Implementation of the Coating of Montmorency
The code of practice for the application of a plaster coating must imperatively be respected. 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.
The support, whose conformity with the regulation of chapter 2.1 will have to be checked, will be humidified to saturation , without surface shine.
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.
The Coating is applied in only one sole homogeneous layer of the desired thickness. In no case should this thickness be lower than 1 inch / 25 mm, once the coating laid . It is floated with a strike, then even up with a smaller blade. One should not remix the coating when hardening has begun.
Particular case of coating between timber frames:
In this particular case, the minimal thickness is of 1 inch/25 mm that which includes the rough-trimming (carried out in Coating of Montmorency) and the top coat ( 9/16 inch /1.5 cm thick minimum).
Particular case of buttering and coating for stones with heads visible:
The use of a rough-trimming plaster is excluded: one will exclusively use Coating of Montmorency on the overall thickness. The Montmorency coating must be filled in the joints up until contact with the rough-casting material, on a minimal total thickness of 1 inch / 25 mm.
After setting, one re-cuts the Coating of Montmorency with a sharp berthelet (or one scrapes with a nail float in the case of Mortar of Montmorency). It can also be brushed or washed after setting (with a sponge or a hard brush). It will then be rinsed in a careful way with water slightly under pressure, in order to eliminate laitance.
In no case, can it be smooth-finished , nor burnished (except in the case of occasional courses: opening frames, belt courses, splayed lintel between stories).
Fresh coating must be protected from direct sun exposure. Moreover, it must remain wet at least a week. If necessary, it is appropriate of re-humidify the coating with clean water and a spray.
Conversely, it is advisable to prevent the coating from remaining wet for too long, whatever the cause is, so that carbonation may be accomplished. When hardness permits, the coating can be re-cut, in particular for joint scoring. Once perfectly dry, the coating can also be sanded or renovated, (including rubbed finishes such as sand-spraying) like a very tender stone.
Of course, the minimal thickness constraint of 1 inch / 25 mm is to be respected, included these works (in the case of dug joint left unfilled, the thickness is measured from the bottom of the joint; in the case of dug joint filled in white or tinted coating of Montmorency, the thickness is measured from the surface of the coating).
2.4 Particular points of implementation
2.4.1 Before coating
220.127.116.11 Change in load-bearing structure
a hollow joint will be placed between the parts of the different load-bearing structures (for example in the case of an elevation).
In the same way, a hollow joint will be placed right along eventual expansion joints (for example, in the case of a brand new concrete realization ).
2.4.2 During the coating
18.104.22.168 External angles
The external angles, for example at the framing level will be are realized at once, or in two times. In the latter case, the surface to rework will be distant at least ¾ inch / 2 cm from the external angle.
Before coating, this surface will be evened by striking it off. In particular, it is formally excluded that this area to rework be comprised in the bisecting plan of the angle.
22.214.171.124 Angles of bays ( corner beads)
A strip of galvanized wire mesh or fiber glass screen reinforced with mesh 9 X 9 for example or a galvanized expanded metal piece, of minimal dimension 12 x 6 inches/ 30 X 15 cm will be sunk in the coating at each bay angle, at the base of the finishing coat.
2.4.3 After coating
126.96.36.199 Protection against localized streaming
In general, surfaces realized in Coating of Montmorency must be protected from any localized streaming, in particular from water drops and back splashes.
The following paragraphs treat of a few particular cases, but this principle of protection must be strictly followed in the construction on the whole of the work details. In particular, as long as the Coating did not dry once and have time to carbonate, these precautions will be redoubled.
188.8.131.52 Horizontal surfaces
Horizontal or quasi-horizontal surfaces of more than ¾ inch / 2 cm of width made in Coating of Montmorency will be obligatorily protected by a cover, for example a zinc coping. Horizontal or quasi-horizontal surfaces of less than ¾ inch / 2 cm of width made in Coating of Montmorency will obligatorily have to present a glacis slant at more than 60° (it is particularly the case for the tops of lintel mouldings ).
184.108.40.206 Backsplash surfaces
Backsplash surfaces, i.e. located above a horizontal or quasi-horizontal surface of more than ¾ inch /2 cm wide, must be protected by a splash board at least 2 3/ 4 inches / 7 cm high.
The preceding provision applies in particular to splashes produced by the windowsill on the jambs. Moreover, a work (weathering) will have to be so that the water collected by the sill will be rejected on the front edge and not on its sides. In the case of a zinc coated wash, an authorized solution consists in raising the side edges of the cover.
220.127.116.11 Wall base
Montmorency coating should not be implemented at less than 20 inches / 50 cm of the ground. It is thus advisable to envisage a base at least this height. It will be on the same facade plane that the coating, or at least will present a glacis at more than 60°.
18.104.22.168 Stringcourses and cornices
the projection between the stringcourse edge at the water droplet level and the coating plane level must be 1 3/8 inch / 3 cm per meter height before the next belt course (modénature), the surface level of the coating being considered just above this last belt course. Thus, in the case of one stringcourse per story, the band width between level n and level n+1, must be 1 3/ 8 inch / 3 cm per meter height of the story n plus the slope of story n.
22.214.171.124 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).
126.96.36.199 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.