Rebating chipboard - how?

11 May 2016
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United Kingdom
Hi all,

Long time lurker, but I've generally been able to find everything I need already mentioned somewhere else...until now!

I'm currently boarding out a small area in my loft around the hatch, and plan to do this straight on top of the joists. (The remaining area already has a raised floor constructed with Storefloors Loftzone and is well insulated).

I am planning to lay some T&G chipboard lengths perpendicular to the joists, but towards the centre of the house, where the joists from either side meet, one joist is raised above the other by about 7mm.

Because I'm after a flush fit, I am currently thinking about rebating a small section in the base of the chipboard panels, to exactly match that of the raised joist. This would require a section 1m long x 47mm wide x 7mm deep to be rebated. I have a 1/2" router that I thought might be my first course of action, but thought I'd check first, in case there is another easier way that I've completely overlooked!

(Another option of course is just to buy some additional thin sections of wood to raise the entire section, but was hoping to avoid this, as I need to re-screw the loft ladder back onto the chipboard after, and am not sure how much height tolerance I have to play with!)

Many thanks all!
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heeelllooo and welcome ray.birch :D:D:D

assuming they are about 4x2" they will be moving all the time when you walk on them
have you tried slotting the flooring together and screwing it down to see what happens ??
Hi big-all - and thanks for the super quick reply!

I've currently got a much smaller piece of chipboard screwed over the top of the joists in question, but the problematic raised joist means that the board does not sit flush to the other neighbouring joists unfortunately.

It seems to be where the house (1930s built) has gradually moved over time, and has resulted in the joists that meet in the centre no longer being parallel to each other, i.e. one side has dropped, resulting in the central part of the joist looking like: /___

(Note that it's that raised top bit which is the problem that I'm talking about!)
in general you can loose 5mm without trying
i personally would pack out joist before using 3.2mm/1/8" hardboard
removing 1/3 the chipboard is a bit much strength wise
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Rebating chipboard will weaken an already feeble material.If you only have one timber causing problems you could run flooring to it, baton either side sitting flooring on baton to meet top of timber with a 7mm fillet insert to keep all flush.
Apologies for the delay in getting back to you guys - I've finally had time to get round to this, and have taken advice on board, and packed out the lower joists, rather than rebate the chipboard. Loft area now looks a damn sight better, and just wanted to say thanks for the advice!
great glad it worked out at least you know it wont give way now lol
thanks for taking the time to let us know how you got on it makes it all worth it (y)

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