Is placing chipboard over floorboards upstairs a weight issue?

[Lalala]

Hi there

I am thinking of using 18mm chipboard to help even the floor in a large upstairs bedroom of a 170 year old house. Would the weight of the additional Layer be an issue potentially? There is no creaking or bouncing currently. Thanks

 

[Mottie]

Surely if the floor is uneven and you screw ply to it, it will still be uneven?

 

[Dereekoo]

If your floor is sound at the moment another 10kg/m2 additional dead load is not going to affect its structural capability. In theory the floor could deflect 1 to 2mm depending on the joist size ,span and spacing

 

[Deleted member 174758]

How bad is your floor and how even do you want it?

18mm chipboard weighs in the region of 50kg a sheet (8x4ft), so in a 16 x 12ft bedroom you'd be adding about 300kg - or about the weight of three large adults.

Normally when floor prepping for vinyl or in some cases solid flooring (engineered, etc) we lay a skin of plywood screwed or nailed (or screwed) down onto the floor boards to level the floor. Plywood is stronger than chipboard and can be nailed or screwed on closer centres 100mm for nails, 150mm for screws - something you can't do with chipboard), resulting in a stiffer floor when finished. Chipboard flooring normally requires fairly level joists to lay onto - I suspect that trying to lay chipboard onto a very uneven floor may become an exercise in frustration as with a very uneven floor you may end up with areas where the chipboard is unsupported and not well fixed, keading to cracki g or creaking in the future.

My advice would be to check exactly how bad your floor is (long straight edge and obtuse light source), the select an appropriate thickness of plywood rather than chipboard

Surely if the floor is uneven and you screw ply to it, it will still be uneven?

Yes and no - plywood will span uneven boards quite well and take out a lot of unevenness; the thicker thevply the better it can cope with major differences between boards. If after plying the floor still has hollows they can normally be taken out by trowelling on self levelling compound then working with a float to almost level and leaving to flow out

 

[Lalala]

I don’t know how to reply under each response but thanks so much. All very helpful. I am planning to ‘prop’ the chipboard or pack under it or whatever term you would use in the are it requires it to even the floor first. I have watched some videos on this and done it downstairs in the room directly below to good effect (so far). I just Wasnt so sure of the weight with it being upstairs.
Any other thoughts on this method greatfully revived. I have been given a ton of 18mm chipboard which is why I have chosen this type of hoard. I can purchase some ply if the difference will be stark over time though

 

[Deleted member 174758]

In terms of packing I'd possibly use multiple layers hardboard and thin plywood - but the way I do it requires access to a laser level, be cause you fundamentally need to build a series of contours starting at the lowest level and getting larger (sort of like the way a hill is shown on an Ordnance Survey map, only inverted. The difficulty with chipboard is that it is rigid and won't readily conform to the floor beneath - but it is also brittle, meaning that if it isn't adequately supported, it will crack and/or sag over time. It will also lift your floor by 18mm, meaning that the door(s) will need to come off and be trimmed

If you have been given full sheets it might be less painful to lift the floorboards, level the floor by adding straight timber to the sides of the old joists (a process called sistering), and then fixing the chipboard to the tops of the sistered joists. That way you get a perfectly level, properly supported floor, but you don't need to cut your door(s) down

 

[Lalala]

Thanks so much.
Layers of hardboard is what we used underneath in the living room actually and seems to have worked well. I don’t think there are any dips enough to crack to chipboard it’s very evenly supported where it needed it. I think anyway!
Time will tell. Perhaps need to be even more vigilant on this then.
The skirtings need removing anyway and we are replacing the door so no bother there. It will be a bit of a step down to the hallway but we lifted that area with some thinner ply as there were bits of boards missing ao just to strengthen rather than even out really - so shouldn’t be a massive difference.
Thanks

 

[foxhole]

Are you trying to achieve a level or flat floor? Or both?

 

[Lalala]

Flat is the main thing because it’s not, but level as poss would be good too if course

 

[Deleted member 174758]

The only guaranteed way to achieve flat and level is to lift the planked sub floor, level the joists by sistering, then relay (or replace) the sub floor (i.e. board it)