I need to close up an existing open porch with a new door & was hoping to sheet around the door with exterior plywood & then render.
Is there any special tricks or sealing etc that has to be done before you plastering over plywood ?
The ply should be covered with a breather membrane; this will allow the timber to breathe but prevent moisture passing from the render into the internal space.
Is the plastering mesh easy to buy ie would B&Q or woodies sell it, I would only need a very small quantity, also is there special fixing for the mesh or can it be nailed to the plywood ?
breather membrane - is this like a seal which is painted on ? Do you know a brand I could use ?
Breather membrane is a geotextile type woven fabrick which is microporous. it's used in timber framed construction and in many roofs as a sarking membrane. Can be bought from most builder's providers. fix mesh to ply with clout head galvanised nails.
Marine ply would be a great material to use alright but it's mad expensive and probably an overkill for this application- it's more usual to use WBP ply in this scenario. WBP is "weather and boil proof" which is how the glue is described and this material is perfectly satisfactory for use here. Marine ply is probably more than €120 a sheet versus €30 (haven't bought it in a while so not sure!!) for WBP.
You'll want a good stable background for any render so I'd say use a 18/ 19mm thickness (3/4") of WBP. 12mm (1/2") would probably be okay for a small area if well braced but why scrimp, you'll save a fiver at most!
Thanks for quick reply carpenter,
1 extra question, because the area is so small approx 1.5 sqm if there any alternative to a breather membrane, or can a buy this in small quantities ?
Can you reccomend a brand for the breather membrane ?
There are many brands of breather membrane, Tyvek being one; unfortunately most of these are likely to come in large rolls. A geotextile membrane like Terram (used in landscaping) "might" perform a similar function but you really would be better off using the proper product. Do you know a builder/ carpenter that would give you enough to do a job? A local timber frame company might oblige?