Home>Discussions>INTERIORS>Molding & Carpentry>Floor joists - sistering and/or blocking
2 posts / 0 new
Last post
Floor joists - sistering and/or blocking

We are going to be tiling our second-story kitchen in our 1920's home. The joists are 2x10's, 16" o.c., with a span of 14 feet. These barely meet the deflection requirements for porcelain tile, and certainly fail for natural stone. We're still considering travertine, and even if we don't go that route, it seems clear that reinforcing the joists is a good idea.

Since the joisting system is completely exposed from below, I'd like to sister 2x10s to the originals, as well as add some blocking. None of the joists appear to be sagging so at this point I don't think I need any jacking and so far this still seems like a DIY job. I spoke to a framing professional about it, and it didn't seem like it was worth his time, so as long as it doesn't require some major jacking, I'd like to tackle it myself.

What I'm unsure about (don't have any framing experience) is the best way to attach the lumber. Reading online, I've seen everything from construction adhesive plus nails to decking screws to bolts/washers, etc. Could anyone be so kind as to spell out your preferred way to do this? Thanks in advance!

Re: Floor joists - sistering and/or blocking

you're right that no major jacking would probaby be required but it would be a good idea to use a jack to get the new ones tight against the sub floor. you have to make sure that the crown of the new joists are facing up and since the old ones have been there for so long you will have a tough time getting the new ones level with the old ones, that's where a jack would come in handy, to push everything into place. then i'd use construction adhesive and nails to secure them together and to finish it off, either blocking or cross bracing. blocking would be easier since you don't have access to the joists from the top to nail them off.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.