Reduce liner size for fire doors?

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Hi all,

We’re doing a project that requires us to replace existing doors with FD30 doors. We have some nice glazed Worcester style doors downstairs but they have been trimmed down to 754mm. Apparently all the off the shelf FD30 equivalents have tiny trim allowances (4mm per door) so a 762mm door can only be reduced to 758mm overall. If necessary is it acceptable to put a 4mm rebate in the door liner to get these to fit? Having bespoke doors made looks to be literally double the price, so apparently I'm looking at at least £1,500 extra and several months wait if I can't solve the problem.

I can't see an issue with this as long as the doors have plenty of hinges and I use decent screws, but wanted to see whether others have done this.
 
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Is the trim allowance because they have veneered edges?

If you're going to fit new door linings, pull off the architrave first and see if there is packing or wedges taking up a gap
 
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Is the trim allowance because they have veneered edges?

If you're going to fit new door linings, pull off the architrave first and see if there is packing or wedges taking up a gap
No, they just don’t warrant that they meet FD30 standards if you trim too much off.
 
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but the door manufacturers define the trim alowance. some doors are made of slabs that are the same all the way through

some doors need to have the lippings cut off before trimming, and put back afterwards.
 
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A fire door is only certified when fitted in the lining that it was tested with, so the lining is integral to the doorset having the FD rating. You need to check what the door manufacturer specifies for the lining.

Having "plenty of hinges and decent screws" does not mean the door will perform as it should
 
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You might not like it but making the opening a bit wider would be cheaper than bespoke doors.

you can buy a dust shield - which has extending poles to reach floor to ceiling and closes off the area.

a diamond disc down each side would do it.

obviously subject to lintels being wide enough
 
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