How can I fix significant splits in wooden siding that is over 80 years old?

[_HumbleJeff]

What is the most effective long-term approach for repairing large cracks in vintage wooden siding boards? The boards measure approximately 10 inches in width. I have previously used latex caulk, which tends to sink slightly upon drying yet remains flexible. I have also tried wood filler, which is very rigid but doesn't have a long lifespan due to the boards' expansion and contraction. Eager to hear your recommendations and advice.

 

[spongebobroundpants]

I know a little bit of woodworking and I your suggest to take the movement into consideration and go for some flexible sealent. Or if you want to keep the look you can go with splines

 

[_HumbleJeff]

I know a little bit of woodworking and I your suggest to take the movement into consideration and go for some flexible sealent. Or if you want to keep the look you can go with splines

Flexible sealant sounds like a smart move since it can roll with the punches when the boards shift. Thanks I will look into this.