Back Painting
Although we are all aware of treating cut edges, some Manufacturers of claddings, linings or trim require part or all of the back and concealed edges (& difficult to access edges) of their products to be painted or sealed (back painted) under certain circumstances. The most common of these is the base of the cladding, particularly at and below the bottom plate near the ground, which is an especially vulnerable spot to splashing and the retention of moisture (in particular timber end grain).
Back painting may be done for a number of reasons;
- Durability - helps protect those vulnerable hard to get at places from moisture promoted material degradation (rot or rust etc)
- Stability - reduces moisture uptake in hard to get at places, which can cause movement
- Aesthetics - reduces moisture uptake in hard to get at places which may eventually disfigure exposed surface finishes, reduces risk of unfinished areas showing due to shrinkage
What you must consider is the degree of risk that a cladding, lining or trim has in any given circumstance. Obviously cladding near the ground and lining in a shower cubicle are the extreme examples, but there are plenty of others to consider. The majority involve moisture but it may not be the only reason, so make sure you check the requirements of the manufacturer carefully.
The greatest difficulty is created by the fact that back painting must be done before the cladding, lining or trim is fixed in place. This means decisions have to be made on site as to who does the back painting, and also when and where? Obviously, partly or wholly pre-finished items are less of a problem than site applied finishing, depending on the degree and extent of finish required before fixing. So is that factory primer enough or are more coats needed? Or is the trim fully primed and the cladding partly primed under the trim?
Finish
The other issue is the level of finish required - do you want the painter to do it or can the carpenter (installer) do it? The carpenter may be OK doing a couple of coats of standard paint but staining may need more consideration. Are there specific conditions required for applying the coatings? These are all things that need considering, resolving and coordinating.
Masterspec painting general sections have now had clauses added to cover back painting, while the exterior and interior painting sections have had clauses added that allow the scheduling of back painted items. However there is always a degree of coordination required between these sections and your project cladding and lining sections.
Master Painters H&S Program
The Master Painters New Zealand Association (MPNZA) has replaced the old hard copy Painters Hazard Handbook with a new web based Health and Safety Program. The new program is very impressive, particularly after the old hard copy which has been difficult to get hold of for a number of years.
Masterspec
Masterspec painting sections have been updated to include the new H&S program and back painting. This includes the painting sections in the Masterspec systems Standard, Basic, Interiors, Landscapes, Structural & Civil and Services.