Everything is all sunshine and rainbows until the Greek styled feature perfectly set up on the wall begins to develop cracks and gaps all over the place, then you start to wonder what must have happened, and possibly question the expansion and contraction of the molding?
Does crown molding even expand in the first place?
As crown molding can be made from wood and even plaster, it has the potential to expand or contract, but such expansion due to material composition is typically very minimal to cause a prominent seam or gap to surface at joints. What normally causes gaps in crown moldings includes building movement, temperature change and impact caused by accidents.
The expansion and contraction of crown molding
Crown molding can be made using different materials, from plaster, solid and engineered wood to polyurethane, PVC, Flex and Polystyrene, and of all the materials, wood is the most prone to dimensional change across its length and width, and even so, the change: be it expansion or shrinkage, is highly minimal to the extent that it rarely ever cause a significant gap at the miter joints and top portion (where crown meets ceiling), provided the wood was properly dried at the factory and therefore lacks the necessary moisture content to cause a dimensional change.
So, if the crown molding itself doesn’t cause gaps that often, what then causes the gaps that we see on them?
This is exactly what we’re going to discuss in the next few paragraphs below.
Why is my crown molding separating from the ceiling? Is it normal?
If you have crown molding that separates from the ceiling, then the most likely cause is pressure. Now you might be wondering what pressure has to do with all of this.
In order to better understand, you have to familiarize yourself with the basic principle that every element in your house is connected to one another.
You may not be able to visually trace a direct connection sometimes, like in the case of roofing and the crown molding.
But there’s certainly an indirect connection going on there, and that becomes apparent when pressure comes into the picture.
In the case of crown molding and roofing, an indirect connection is established in the following manner:
Crown molding>wall/ceiling>studs, beams, rafters>roofing
So when you have a system consisting of an intricate connection like this, pressure applied from where it can be tolerated, will certainly distribute across the network, and how much is distributed as well as the effects it has of different elements of your home depends on the magnitude of the initial pressure.
Take for instance, in winter, when snow accumulates on your roofing, this adds extra weight to the roofing (which has to be distributed across to other parts of the building to maintain equilibrium), and as such, you have pressure distributed to the beams and studs in the walls, until it reaches the ceiling and walls which cause them to shift position and ultimately cause a relative displacement of features and fittings attached to them, for instance, gaps in crown moldings.
Aside from snow, there can also be soil shifts caused by changing moisture levels which can result in the shifting or sinking of the building’s foundation which then affects all other components that depend on it accordingly.
How do you fix a gap between a wall and trim?
The easiest way to fix a gap between the wall and the trim is to use caulk. Caulk is simply a compound that is used for sealing joints and seams in various structures and fittings at home.
The way you apply caulk is simple. Run a bead of it across the seam or gap and use your hand to smoothen things out. You don’t have to fill up the gap all the way to the inside, just touch up the surface until it closes as going for the latter means you’ll end up wasting a lot of caulk for something the former could easily provide the same visual satisfaction for.
Why are there gaps in crown molding?
You can also have gaps in the miter joint where crown moldings meet. This can be the result of pressure as we have explained above, and can also be the result of change in temperature or even impact.
So how does temperature affect crown molidng?
The way temperature affects crown molding is still related to pressure. When you have structures like beams that are made of metal and can expand with increase in temperature and contract with decrease in it, then you will have a shift in structures like walls and ceilings going on which would invariably affect fittings like trims.
You can also have wood itself expanding and contracting, although the expansion and contraction of wood or even any other material used for crown moulding would not really cause a significant seam or gap to become evident most of the time.
And when it does, it’s not typically something that cannot be caulked!
When it comes to what you can do to prevent the effect of temperature change from affecting your crowns, the answer is not encouraging. There really isn’t much you can do. You could try maintaining a consistent climate inside (which can be hard) so that there isn’t so much temperature fluctuation that can cause expansion or shrinkage, but what’ll happen to the beam from outside will still happen anyways.
And then we have impact, which basically implies that a force of some sort was applied to the crown molding which cause a separation to occur at the miter joint or cracking along its width.
And again, for these, if you have a crack along the width, you want to fix that with glues and then caulk.