Oak Frame finishing detailsPosted on September 25, 2015
In the corner this issue...
Dealing with shrinkage.
I think it is fair to say that these days, in the construction industry, it is common knowledge that green oak moves. A bit. Sometimes a bit more than a bit. This is often a cause of concern to those predisposed to the conventional 'just use brick & block' approach and others besides, and this is understandable - after all, who wants their nice new walls to start developing cracks?
However, the movement of green-oak frames need not be a problem, there are simple rules and details to follow that will nigh-on negate these issue altogether. We're going to focus on the issue of plasterboarding up to a green oak frame now.
The problem with just butting up a sheet of plasterboard to, say, an upright Oak post, and then skimming it right up to said post is that the Oak will dry out gradually, to the tune of about 5% of it's width. It can also twist a bit. This leaves an unsightly gap at best or cracks and bits of skim falling off at worst.
There are two good solutions to this problem. The first is to ensure the Oak never has a chance to do this in the first place. The following picture shows a detail of our encapsulation system (posh word for a pre-insulated external wall and roof structure) around an oak frame. As you can see, there is a 15mm gap between the Oak frame and the panel, leaving enough room for both the plasterboard and the skim finish behind the posts etc. The advantage of this is that skim goes completely behind the oak frame, leaving a nice even line even after the oak has done all it's moving about.
The second solution is particularly of use where you have no choice but to plaster/skim right tight up to the Oak frame. In this case we suggest using a plaster stop bead, set a minimum of 5mm away from the Oak frame, with 3-10mm expanding-foam tape (a quick internet search will give you plenty of info on this tape) adhered to the oak-facing side of it. This way, even if the Oak does move it is not going to be pressing up against that brittle skim finish, and you will always have a fairly even black line, rather than cracks and jagged lines.