Loft flooring question

[Evergreen]

Hi all

I’ve just laid a 5m x 2m area of loft flooring using B&Q’s “Finnloft Click” system. The panels are made of OSB 3 with interlocking grooves on all four edges. In practice, you have to trim one short edge for fixing over 600mm joists and then just butt the ends together. Each plank is 1220 x 320mm and although it’s only 15mm thick, it’s plenty strong enough to take me jumping on it.

The instructions suggest fixing with 4mm x 38mm screws; the number of screws per panel is unspecified. I found it most practical to use only 2 screws per panel, inserted across the middle joist that it spans.

However, now that I’ve finished, it’s just dawned on me that there’s no allowance for expansion. In the past, I’ve laid 2 laminate floors and the instructions made much of allowing a 10mm gap all round for the interlocking planks to expand. The Finnloft Click panels interlock in much the same way but I’ve just gone and screwed them to my joists so they can’t move!

I’m a bit concerned because the inside of a loft gets as hot as a baker’s oven in summer so there must be quite a bit of movement – but maybe all the roof timbers expand together so there’s no problem?

Any advice would be much appreciated.

Regards.

 

[OLD]

Difficult to say i think you will have to monitor over time. Redrilling the screw holes oversize and provision of expansion gap in the chipboard should deal with it if required.

 

[mack9110000]

If your loft gets as hot as you say, the only problems you'll have should be ones of shrinkage as opposed to expansion.

 

[gwaithcoed]

I laid about the same area in both of my daughters lofts some 5 years ago.
Never thought about expansion problem until I read your post, however neither seem to have had any problems.

Alan.

 

[Shultzy]

Evergreen, Found this site on OSB

http://www.osbguide.com/osb.html

this does suggest to leave an expansion gap but maybe only for 8x4 panels.

How does OSB perform under high humidity conditions?

OSB like all wood products reacts to changes in moisture and humidity conditions. OSB is required by North American Standards to maintain its strength and stiffness performance under normal humidity conditions, also referred to as "standard conditions," which are represented by a temperature of 68 degrees Fahrenheit and 65 percent relative humidity. This condition is typical of protected construction.

In addition, OSB is required to maintain its strength and stiffness performance when exposed to weather during long construction delays. OSB panels intended for construction are marked Exposure 1 for durability in accordance with voluntary product standard PS 2-92 (or Exterior Bond if stamped to meet CSA 0325).

Remember to gap OSB panels to allow for possible expansion.

 

[Paul Chapman]

Evergreen, if you put as much junk in your loft as my wife insists on putting in ours, you'll never be able to see whether it's expanded or contracted :lol:

Cheers :wink:

Paul

 

[Evergreen]

Thanks for the suggestions, guys. Fascinating link, Schultzy!

I guess mac9110000 has a good point that the high temperature inside a loft in summer time is likely to eliminate any moisture content and, if anything, shrink the OSB. I can check it twice a year - when I get the suitcases down for summer holidays and then at Christmas when I get the decorations down.

Regards.