Large tapered gap to fill between wall and frame

8 Aug 2017
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United Kingdom
I am fitting an new external wooden door frame in an old brick outhouse. Both walls of the outhouse are quite out of true, so my new door frame has a gap of about 2cm at the top on both sides. It fits fine at the bottom on both sides.

What is the best way to fill the tapered gaps? I have put small wedges of wood in between the frame and the brick to pack out, getting wider at the top.

I have been reading about foam fillers and am wondering if that is the best solution, although I have found foam fillers difficult to use neatly in the past.

Many thanks for any suggestions.
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It’s much neater if you use a gun. Once it’s cured you can cut it flush and cover it with a bit of wood.

I am thinking I may just try and mix up some sand and cement mortar to try and fill the gap. The depth of the door frame is about 45 cm so hopefully I can push the mortar in as far as possible and taper it off as I go down the frame.

Just hoping the cement will hold firm between the wood and brick and will not crack.
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The problem with sand and cement is that it invariably cracks and even falls out over time (especially if you gave a door slammer in the household).

As an alternstive to foam on fire doors we tend to pack gaps such as this with mineral wool then fill the last 10mm to the surface with fire mastic, so as an alternative you could use a material such as mineral wool to pack the core of the gap as needs be then finish with something like silicone or a acrylic decorators filler
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