Lath and plaster wall how to#

It would need to be applied very thickly to really act in an insulative capacity. The hemp I've used was chopped hemp 'shiv' rather than fibres and creates a porridge like consistency which has a small thermal benefit. I've plastered with hemp and lime and it goes on really well. This fiver is ready available and quite cheap and i think i can use that to great success. My local church has been painted this summer in a traditional fresco (mineral paints directly over fresh lime plaster) and they reinforced the plaster with hemp fiber (the kind used by plumbers in pipe joints), basically a hair like thing. I know in the US people used sometimes this expanded mesh alone as the lath, without any wooden lath. Some people have used expanded mesh but that tends to be pretty expensive around here. The second key is obtained in the plane formed by the bottom lath faces where the plaster oozes thru the mesh into the lath spaces.Īn alternative to fiberglass mesh is galvanized steel mesh which is much stronger but i'm not sure i want to use it? The traditional key is formed in the plane formed by the top face of the lath, by the plaster oozing inbetween the lath and forming 'mushrooms'. I could densely staple that to the underside of the lath so there is a double key. I could compensate by using some mesh, for example the ubiquitous fiberglass mesh used to reinforce plaster over insulation (EPS). I know historically people used small split green branches of chestnut but i don't have any source of it. Whatever is available is sawn wood, mostly fir or spruce, maybe some pine. I really don't have access to riven oak or chestnut (mostly due to jaw dropping prices for the wood itself, not to mention the splitting). Also don't apply your coats too thick or the weight will pull the plaster down before it dries. The work can be done in two coats but you won't get such a smooth finish. The finish coat being very thin and often applied in two passes. Most high quality work was in 3 coats - scratch coat, floating or levelling coat and finish coat. Later coats maybe a 3/2 mix with finer sands or even pure lime or lime with chalk or dust for the finish. Once the first coat has stiffened up you should scratch it in a diamond pattern to provide a key for later coats.

It can help to use a small narrow based trowel to get equal pressure and reduce wastage of the back edge (again often on to your head!). Try to work in thin coats, trowling diagonally across the laths and applying quite a lot of pressure to force the plaster between the laths and creating nibs above to hold it. The fibres give the plaster its strength, reduce cracking and strengthen the 'nibs' or the plaster pushed through the gaps in the laths. Traditionally this would be animal hair although you can use modern alternatives. The plaster should be a mix of lime putty and sharp sand for the base or scratch coat in a ratio of about 3/1 with the important addition of fibres. If the surface is running wet the plaster will slump away (often on to your head!). The lath should be dampened prior to working to reduce shrinkage cracks but it should be allowed to soak in the moisture. Mild steel may corrode in the caustic environment of the lime plaster and cause the laths to fail prematurely. Laths are fixed to the joists with reasonably large headed galvanised nails and spaced about a little fingers width apart. The riven wood also gives a better key for the plaster. In England lath is traditionally riven oak or chestnut, riven wood being thought to be stronger and more flexible than sawn. Where's a certain light colored cloud when you need one ? I need info on these subjects, pros / cons, anything. Or maybe something else to replace the wooden lath, maybe metallic or even resin / plastic fibre / netting ? Or maybe screws, or staples (galvanized presumably) ? Needless to say, most wood available is green, which could be good or bad (but with our low knowledge of how wood works, it's mostly bad). I have access mostly to conifer wood (spruce, fir, pine) which comes in good prices.Īnd the wood laths, should they be green or dried ? Traditionally, lath was made of wood (rive in the beginnings and sawn later on).

Lath and plaster wall how to#

The good craftsmen that knew how to do it right are gone (either in time or space) and my questions don't have clear answers. What i'm having difficulties is in realizing how it's done. So, putting lime plaster thru lath seems like a lot of work but has other advantages (like it's more healthy). I could go for the 'regular' drywall which would make my life simpler in the very short term (installation wise).īut drywall has some problems in being sealed to reach air barrier status. I'm pondering a lath & plaster (lime) ceiling for my soon to be built house.