I know it sounds silly, but how much does it weaken a joist to screw sideways right through it ? If I fitted noggins (extra support for plasterboard) between joists but flush with the bottom of the joists, by screwing right through the 3 inch joists and into the noggin ends, how much would it weaken the joist ? What about drilling small holes near the bottom of a joist - say for a screw pilot hole. Or drilling a countersink for the screw ? I want to make sure the BCO doesn't turn up and say I've wrecked my roof supporting joists. Should I devise another fixing method ? Thanks, Simon.
You will not weaken the joist - in fact, if you really stop and think - you are in fact reinforcing it!
When you thing plumbers, electricians, carpenters and all and sundry, drill through joists for there relevant bits of pipe, cables etc to go through (and usually in the centre or top third) then how are small pilots going to affect the strength of the thing?
He's go more intelligence and experience to say that.
If you are simply fitting noggins, then the usual way is to screw or nail at an angle through the side/end of the noggin then into the joist. Not screw through the full thickness of the joist into the noggin end. At time of house build, nailing noggins in place is OK. If you have ceiling/wall attached, then hammering will cause nail heads to pop out and all-sorts. So best pre-drill noggins and pilot into joists for screws.
Dear Simon It all depends where you put the screw! If it is in the top half of a beam then you are not weakening it If it is in the bottom half then there is a weakening effect but only so much as the shear stress parting the longitudinal fibres in the bottom tension zone which is likely to be very little. The nearer the bottom you get the worse the effect. You can ignore the top 75 % of a beam for all practical purposes as being at risk should you put screws in. What do you mean by roof supporting joists?? I assume ceiling joists and if so and you are concerned use full length noggins and fix in the middle (neutral axis) or if you want to be anal use joist hangers (a silly over reaction to a non-problem but theoretically an answer)
So is there any recommendation for how far into the joist to screw ? I have to fix the noggins near the bottom, but I don't want to fix them below since this would reduce head height. I guess it may be the best idea to use a fixing that hangs the noggins, so the screws are in the centre line of the joist, e.g. joist hangers or a timber block. Cheers, Simon.
sm snipped-for-privacy@hotmail.com coughed up some electrons that declared:
I can highly recommend 5x80 or 5x100 ScrewTites. Upon a previous recommendation here, I used a load of 5x80's to do some studwork, very successfully (beat nails hands down, times lots).
Needed to fix some 44x94 (2x4") to some ceiling rafters and I found that the ScrewTites worked just as well there. No pilot hole, easy drive, good pull together and good grip, and head self countersinks. This may not work if your joists are oak!
Anyway, as my upstairs floor is a bit of a disaster area, I'll be adding some noggins for cross-bracing to stiffen up the dodgey areas. I plan to stick some 2x4" in as noggins, level with the top of the joist in my case (bottom area fouled with random wood). For the fixing I would just screw a couple of ScrewTites in horizontally into the end of the noggin from the opposite side of the joist. They hold fine in the end grain and without a pilot hole, they form a pretty effective peg.
Unless anyone tells me that's wrong... But having used them, it seems like a reasonable idea. I'm relying on these to add structural stiffness. For your application, they will definately be a suitable fixing method without any doubt. No vibration either :)
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'll need a power screwdriver, but a small one like the little Bosch will suffice - they are lubricated and drive very easily.
The Natural Philosopher coughed up some electrons that declared:
I would debate "quicker". A ScrewTite pops in in a few seconds in one easy motion. Certainly no slower than nailing.
I reckon it's equally as sound as a nail for lateral support (it's the same size with no hole slop so it should be, and way better able to resist pulling forces.
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