I'm intending to board out my loft for light storage, and have just reached the stage where I'm going to insulate the loft floor. My current joists are 38x63mm, so there's no space for rockwool insulation at the moment.
I'm trying to decide whether to go for something thinner like kingspan, or whether to raise the joist level by adding more wood to the top. What I wondered is, would adding more wood to the top of the joists (say another 38x63mm timber) add to the rigidity and strength of the joists, or would the extra weight make them weaker?
If I were to add to the top of the joists, the extra timbers would have to be in a couple of sections as the span is too great for a single piece, but they would be supported by the existing binders and hangers from the purlins - does anyone have any idea what effect this would have on the strength?
Any advice/suggestions that anyone could offer would be much appreciated - there certainly seems to be plenty of expertise in here.
I'm trying to decide whether to go for something thinner like kingspan, or whether to raise the joist level by adding more wood to the top. What I wondered is, would adding more wood to the top of the joists (say another 38x63mm timber) add to the rigidity and strength of the joists, or would the extra weight make them weaker?
If I were to add to the top of the joists, the extra timbers would have to be in a couple of sections as the span is too great for a single piece, but they would be supported by the existing binders and hangers from the purlins - does anyone have any idea what effect this would have on the strength?
Any advice/suggestions that anyone could offer would be much appreciated - there certainly seems to be plenty of expertise in here.