what can I fix this architrave to?

[redhexagonal]

So I have a door frame that is made of 20mm timber, and there is a gap next to it which is filled with a bit of timber , set back by 8mm at the top and 4mm at the bottom, and then some plasterboard another 12mm further back (see photo) . How can I build this up enough to fix the architrave to? The 20mm timber isn't enough to fix my 70mm bullnose architrave to .

 

[Wayners]

4mm multiboard like tile backer you can buy.
Cut to fit and stick in but will need to pack out to 12mm at the one end if I'm reading right

 

[redhexagonal]

4mm multiboard like tile backer you can buy.
Cut to fit and stick in but will need to pack out to 12mm at the one end if I'm reading right

trouble is the timber isn't set in plumb so its set back more at the top than the bottom

 

[Deleted member 174758]

trouble is the timber isn't set in plumb so its set back more at the top than the bottom

It doesn't matter - you work to the door casing/lining and either caulk the gaps or add tapered strips to the back edges of the architrave before installing it

 

[redhexagonal]

It doesn't matter - you work to the door casing/lining and either caulk the gaps or add tapered strips to the back edges of the architrave before installing it

I need something solid behind the architrave to nail/glue it to, do you mean strips of wood on the back? I'm not sure how to make tapered strips.

 

[Deleted member 174758]

I thought you were going with Multiboard pinned (opening side) and glued (plaster side) to give you something to attach the architraves to

 

[redhexagonal]

I thought you were going with Multiboard pinned (opening side) and glued (plaster side) to give you something to attach the architraves to

maybe I didn't explain properly - the timber is jammed a bit wonky between the frame and the stud work, its not plumb or flush with the door frame, so I guess I need some kind of tapered material to fix the architrave to. I have a lot of small offcuts of wood I might be able to glue/pin to the timber to get a flush surface with the frame, but it could be fiddly. i also thought about pinning/glueing up a bit of stripwood and then sanding it, but it could take a while

 

[Tigercubrider]

I don’t really understand the issues?
couldn’t you gripfill some kind of thin MDF strips into position then gripfil the architrave?

 

[redhexagonal]

I don’t really understand the issues?
couldn’t you gripfill some kind of thin MDF strips into position then gripfil the architrave?

how would I make the mdf strips?

 

[Tigercubrider]

Cut a sheet down.

 

[redhexagonal]

Cut a sheet down.

do you mean cut tapered strips off the side of a sheet?

 

[Tigercubrider]

Cut the strips, fix them to the gap and trim when dry

 

[redhexagonal]

Cut the strips, fix them to the gap and trim when dry

How do I trim them when they’re stuck to the timber?

 

[Why Not Indeed]

Perhaps annotate your picture with what you intend to stick where, and a picture of the architrave.

 

[Tigercubrider]

with a saw, run on the wall surface? any slight variation would be hidden by the architrave and filler