Ply overboarding

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williamglossop

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Further to Dazlights advice, i have a P5 chipboard floor that i am going to overboard with 5.5mm ply prior to fitting Camaro LVT.

There are a few dips in the existing chipboard that i want to level out. Would it be best to use a suitable SLC over the chipboard first, then overboard with ply and then use feather finish over the ply joints and fixings..... or is it better to lay the ply down first, before slc, and allow the dips to transfer through to this and then use slc over the ply.... just wondering which way round.

Previously ive used ring shank nails to overboard.... is this the best fixing? Bear in mind its 50 sqm.

Also - when laying herringbone - i have a T shaped space to fill. Does it look ok to have the floor direction running up the spine of the 'T' and then turning 90 degrees to the left into the left room, and 90 degrees to the right into the right room..... or is it more asthetic to keep the direction constant. There is no divide between the rooms. Basically, imagine the spine of the 'T' is the hallway, the left bit of the 'T' is dining room, and the right bit of the 'T' is the kitchen.
 
Chipboard is prone to cracks and dips.

Consider flinging it into the skip and replacing with ply, with struts under all cuts and joints
 
It's brand new caberdeck that's glued and screwed to the joists. I cant rip it all out, plus I've had 15 sheets of 5.5mm ply delivered now too. Not to mention to sickening cost of thicker ply.
 
No, its not defective - one joist is just a little bit high, and another is a little bit low at the other end. Its created a slight (few mm) dips in the floor. Its absolutley rock solid though.
 
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JohnD said:
Chipboard is prone to cracks and dips.

Consider flinging it into the skip and replacing with ply, with struts under all cuts and joints
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I'm beginning to think you need to see someone about this hatred of chipboard, John. It's becoming an obsession ;)

Chipboard or no more prone to dips than plywood (from experience) - in both cases if there is a dip or crown in the joists the flooring will follow the joisting if correctly installed. As to cracks, how is that? Never seen a chipboard floor which has been properly installed crack. The issue is almost always one of installation quality, not materials

williamglossop said:
Not to mention to sickening cost of thicker ply.
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That, and the gawdawful quality of a lot of 18mm hardwood plywood we see these days is another reason to bin the idea of using plywood for sub-flooring. John is still living in the 1980s when good quality plywood was relatively affordable, T&G chipboard was not available, and PU glues and nailers were a thing of the future. BTW the last show grade 18mm birch plywood I bought was £172 a sheet (PLUS VAT). But against the intumescent lacquer we had to coat it with (3 coats at £700/drum) it was chicken feed

williamglossop said:
No, its not defective - one joist is just a little bit high, and another is a little bit low at the other end. Its created a slight (few mm) dips in the floor. Its absolutley rock solid though.
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Doesn't sound that bad. I'd fix the plywood down then SLC. Normally I'd use screws (at 150mm centres) to fix the plywood, ring nails should be OK, too - just make sure there are no services where you are fixing, or that it is below the maximum reach of your fixings.
 
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I used to lay thin plywood sub floor with 16 gauge narrow crown staples for the floor layers at one time, but that fell out of favour when I simply couldn't get the (Paslode) staples that easily any more. TBH I'm not sure if 18 gauge are up to the task. These days I screw (collated screw gun) - on the thinner stuff I often use drywall screws as the bugle heads sink more cleanly in thin ply
 
Experimenting with 18 gauge nails about 9 out off 10 the head would pull through it wasn't until fixing length was less than around twice the material to be fixed size that the heads resist the pull out
in other words 8mm pine cladding through the face [not the v]would need only around 25mm to get the most pull out and as you can imagine 16mm on a pull out wont give much resistance so iff we assume the shank at 7mm will give you nearly half the resistance leaving the head to make up the other 9mm
so perhaps on 5.5 ply plus the head would give you perhaps [5.5+9=14.5] so anything above 30mm would be wasted as the pull out resistance would exceed the head resistance
now not scientific and hard faced ply may have a bit more pull out resistance but it gives you a rough idea
now i am talking about the very small "T" head nails
as an aside 32mm is more than enough to hold t|&g in the groove because the sideways pull is more at an angle
and iff you find my calculations confusing thats all off us then :giggle:
 
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