Lifting the height of an ali bi-fold door

[chriselevate]

A company are looking to refit a set of bi-fold doors for me.
I need the internal level to an additional 25mm higher than they currently are.

They have said that they will use a - knock on/frame extension/add-on in order to increase the height by 25mm.

Is this something that is standard and should be done?

Thanks

 

[foxhole]

Can be lifted with packing or as described, not important wants under it as secured at sides and top.

 

[chriselevate]

So would the 25mm knock on/frame extension/add-on be under the cill of the bi-folds or on top? He wasn’t to put to put the cill down first followed by the add-on and then sit the doors on top. Is that right?

 

[foxhole]

Normally used at the top but could be used underneath , why does it need raising?

 

[chriselevate]

“Normally used at the top but could be used underneath” - when you say top do you mean top of doors or top of the cill?

Needs raising as my internal height is currently level but I need 25mm more height inside to install underfloor heating.

Attached are photos from inside if that helps show. There are two sets of these bi-folds that need replacing. Just want to get them right as it’s an expensive thing to get wrong.

 

[chriselevate]

The doors are being replaced as the previous owner fitted them badly, the configuration is wrong, no cill was fitted to the ones with the engineered floor! as well as needing more height inside. Just in case you wondered why they were being removed

 

[foxhole]

Normally on top of door to give clearance for trickle vent .

 

[chriselevate]

How would you suggest getting a higher threshold inside so I can get 25mm of underfloor heating to go down? Thanks