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Carpentry & Joinery Question
I need to cut 60 mm out of a 200 mm joist. what do i need to strengthen the joist
You don't say if this is 60mm deep or 60mm wide but lets say its 60mmx60mm, this will leave you 140mm on the joist, you could plate either side in steel, say 10mm mild steel, if you got 2 pieces cut at 1000mm x 130mm and had 2 rows of holes made along its length about 150mm apart. You could then clad the joist splitting the steel evenly over the cut out and drill through to allow m10 bolts and nuts to go on with washers, tighten up fully with a rachet socket and that won't budge.
This is probably overkill for what you need but it'll prevent any flex in the joist, if the rest of the joists are not being cut you might not need to do anything as they will spread the weight, 140mm is still a decent joist size.
Again you might get away with nailing some c16 grade timber (5"x2") onto either side depending on how much weight will be on it and how big/long the cut out is.
Hope this helps
Answered 26th Aug 2011
Again depending on width of 60mm cutout and weight of load, you could cut two lengths of 3/4 ply , say 1mtr long shaped to joist incl cutout ,then laminate both sides using resin glue and screws/bolts.
Answered 7th Oct 2011