How long should moldings rest before being cut/mounted?

[Vermilion]

I've bought new moldings for a room and have them lying on the floor in that room. How long should they stay there to prevent them from shrinking later? What is the minimum time?

 

[MathiasS]

...is it a trick that works in reality?

The moldings, like any other wood, will move throughout the year as humidity changes.

I nail and glue (even end grain) moldings and then apply a flexible sealant before painting the final coat of paint, then I seem to avoid cracks, etc., regardless of when during the year I install the moldings.

 

[Vermilion]

...is it a trick that works in reality?

The moldings, like all other wood, will move during the year as the humidity changes.

I nail and glue (including end grain) moldings and then seal before I paint the final coat, which seems to prevent cracks, etc., regardless of when in the year I install the moldings.

Yes, it works, sitting in a room where I have the proof around the windows. I bought moldings for 2 out of 3 windows and put them up relatively quickly without thinking they should rest. It ended up with me getting gaps of 2mm between the 45-degree cuts that I had to fill. The third window, I bought molding for later, but I was super lazy to fix it, so it sat there for several months, cut it, nailed it up, and it hasn't shrunk a bit. However, I wonder what the minimum time is for the moldings to acclimate before you put them up.

 

[MathiasS]

Okay, and how does the fact that I've made countless windows and doors and never let anything rest before I install the moldings fit into the logic here? No cracks.

I believe it's more important not to buy wet timber than to let things rest... and to install them correctly.

 

[ArneTW]

It depends... a few days... a week.

Look at how it has been stored by the seller, outdoor storage or indoor.

/ATW

 

[ArneTW]

Ok, and how does the fact that I've made fifty-odd windows and doors and never let anything rest before installing the moldings fit into the logic here? No cracks.

I think it's more important not to buy wet wood than to let things rest... as well as installing them correctly.

You always buy indoor-stored moldings... or maybe you're not as quick to put them up as you think...

I always let moldings rest for a couple or three years before I attach them.

/ATW

 

[MathiasS]

It varies. In recent years mostly stored indoors. However, I see a clearer correlation between how I've installed them than how the moldings have been stored.

Where I haven't glued and nailed the moldings + glued the end grain where the moldings are mitred, there are cracks, always, sooner or later. Where I've done it "right," it's *very* rare for it to crack.

 

[Vermilion]

The ones I bought are from Byggmax and they are stored outdoors under a roof, it might be wise to give them a day to feel at home

 

[davveno1]

They usually lie for a week or so.

 

[myrstack]

I believe the moisture content in the moldings is more important than the time they are allowed to rest. If you buy moldings in the winter that have been in low indoor humidity for an extended period and install them, they are more likely to swell rather than shrink after installation, and a miter joint will probably be more likely to close rather than open. Such a glued joint usually holds up okay.

If you buy something that has been in high humidity and will dry out after installation, you are likely to get miters that open up, and probably a glue joint that will be too weak to hold. I try to avoid hardware stores that sell moldings from their cold storage/drive-in as I find these can be quite moist.

Regardless, gluing and fastening properly is essential.

 

[Hybro]

Those of you who are experienced might know why wide moldings, like around a door, perfectly mitered upon installation, often crack on the inner part of the miter, but rarely on the outer edges where the moldings meet?

 

[Snickarkirre]

Those of you who are experienced might know why wide trims, like around a door, perfectly mitred at installation, often split in the inner part of the miter but rarely at the outer part where the trims meet?

It's because the trims shrink more in width and almost not at all in length. This causes the gap to be larger in the inner corner and the outer corner to become tighter.

 

[Hybro]

It is because the frames shrink mostly in width and almost not at all in length. This causes the gap to become larger in the inner corner and the outer corner to become tighter.

Correct