I have a 20-year-old building with approx 1,000 sf of flooring made of nominal 2" x 10" pine planking, with 3/4" plywood subflooring, supported on on 2x10 joists @ 16" OC.

There are cracks up to 5/8" wide between the 2" x 10" planks. For original installation, the cracks were filled with some kind of material that appears to be combination of sawdust and brittle caulking, and which has broken, cracked, and come out of most of the cracks.

I need a caulking or filler material for the space between the cracks which is 2' deep and up to 5/8" wide. This filler material must harden sufficiently for the floor to be sanded and polyurethene coated after the cracks are filled.

Because of the 2" depth of the cracks, I envision some sort of less expensive backer material placed into the bottom portion of the crack, with the exposed caulking required only at the upper portion of the crack (maybe the upper 1/2"?).

I am somewhat familiar with the old shipboard method of sealing decking cracks with what appeared to be oakum and tar pitch, and I am thinking about using some similar method, with modern materials.

Do you have any experience or advice about the best way to seal these cracks, and the materials that should be used?



Thank You,


John Miles
450 Kenal Road
Ridgeway, SC 29016

tel: (803) 786 2596
email: jmiles@milesengr.com

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I had a floor similar to this. I used strips of wood a a backer rod and for the smallest gaps I used shish kebab skewers to back those gaps. If you are going to completely resand then any trowel fill filler that is compatible with the finish system you are using.