Different Size Floor Joists

by Eliot Johnson
(Kent England )

I am renovating my dads house for him and after having ripped everything out I am now on to the structural side of things.

I need to nog out the first floor joists and prepare them for new floorboards and plaster board ceilings underneath too.

It is a really old building and has different size floor joists that are really throwing me off!

Could I use a smaller bit of timber than the joists depth and flush one with the top of the joist flush for the floor and directly underneath that flush one with the bottom for the plaster board would that be acceptable

Please help done great progress until this and once I can resolve the problem I'm back on track?

Thank you very much in advance for any ideas and help


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Jul 08, 2017
Different size floor joists
by: Gary

Hi Eliot,

Sounds like a nightmare, I had the same problem in my Victorian cottage that I renovated a few years ago. Luckily for me, it was on the ground floor and so I was able to find the highest joist, and then pack the others up to the same level.

For your different size floor joists, it will be a little more complicated.

For the underside, that will be plaster-boarded and I assume skimmed with plaster you will be able to get away with a little more. For this I would possibly rip down some scrap timbers to different thicknesses and tack them to the underside of the worst areas to level it out as much as possible.

The most important one to get right will be the upstairs because the floor needs to be flat otherwise it will stand out when walked on. You could try and use the method above, and also like you mentioned bolt timbers alongside the existing joists to raise the bearing up.

The place to start would be at the doorway, because you probably won't be able to change the level here or you will end up going out in to the hallway too and it will become a never ending story..

I would be aiming mainly to get the floor flat, you may not be able to get it perfectly level but that is generally a quirk with much older properties.

If you are using 22mm chipboard flooring and the joists are 350-400mm apart you shouldn't need too much in the way of noggins, just around the perimeter? More inf about noggins here

Hopefully that's enough to fix your different size floor joists let me know how you go?

Feel free to post some pics too.



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