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Community and Q&A

Caulk gaps in timber frame?

jeff_slocum | Posted in Energy Efficiency and Durability on

  We recently bought a 25 year old timber frame. Some timber members have gaps between them up to a 1/4″ enabling me to see the 1 inch blue rigid foam insulation on the outside. We’re in climate zone 6 and I can feel slight air movement near these gaps. Is there anything wrong with sealing them with caulk? Does is increase risk of rotting the timbers?

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  1. walta100 | | #1

    Without some photo it is hard to be sure we are on the same page about the gaps and what to do please post a few.

    Is water collecting in the joints?


  2. jeff_slocum | | #2

    Sure thing. No water collecting in the joints. The picture has an example corner. There are gaps above and below each beam. The ceiling is 1 1/2" tongue and groove, the bevels underneath form a groove that also goes out to the rigid foam. There's sheathing on the exterior side of the rigid foam, on the exterior side of the sheathing is some kind of blue fabric, and then cedar shakes. I've already caulked a few sections on advice from the kit company that made the house. Today I saw a comment on another site that thought caulking these gaps was a bad idea as moisture is trapped in the groove. Given that air is coming in through these gaps, wouldn't any moisture dry to the outside?
    The caulk in the sections that were done is making quite a difference in terms of comfort and the amount of time the water circulators are running. I'd like to keep going if there's nothing wrong with doing so.

  3. user-6184358 | | #3

    Keep on filling the gaps. The air movement is the biggest problem. Make sure to look at the outside for gaps that let the air in, they may also let water in. Your on the right track. An air sealed house is more comfortable. Use the caulking the kit company recommends.

  4. user-2310254 | | #4

    Large gaps should be filled with backer rod and then caulked. You probably want a high-quality polyurethane caulk.

  5. plumb_bob | | #5

    Gaps that move as the wood expands and contracts are unavoidable with any building system that uses large chunks of wood, like log or timber. Most modern timberframes will have the timber super structure wrapped in a non structural skin or some sort, so the movement does not lead to air sealing and insulating problems. Log homes can be chinked.
    For your gaps, the use of backer rod and then some form of flexible sealant should help. For large gaps think about using a log chinking product like permachink, it is designed to handle the never ending cycle of contraction and expansion. Emseal also makes a log home expanding gasket tape that could be helpful.

  6. jeff_slocum | | #6

    Thanks all, I'll keep caulking then. Permachink looks interesting. I've been using GE silicone. It has +/- 50% expansion/compression. I'm thinking that's ok given that I'm caulking when the gaps are the widest and given 25 year old timbers, we should be down to seasonal movement. I'm hoping the gap I see between sheetrock and timber averaging 1/16" is an indicator of movement over time and the silicone is flexible enough for that. If you think that's grossly naive, please let me know.

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