internal door apertures in blockwork walls

[Tom]

So, blockwork starts for the internal walls in the next few days and just setting out now. I'm going for 826mm wide doors - how wide should I be making the apertures? I plan to line the openings with birch ply. The plans show an aperture of 916mm - so 90mm wider than the doors. Is this right? I was guesing I'd line with 18mm ply - is this thick enough to take a rebated hinge? Two layes of ply would be 36mm so would leave a 9mm gap each side - which still seems a little much. Or perhaps should I line with a cheaper/thicker bit of timber first then a final lining of say 12mm ply?

Any advice gratfeully received!

[markc]

Door width plus 3mm gap each side, plus carcass thickness (x2) plus allowance for packing off blockwork, say 10mm each side. 

[Mr Punter]

You may be able to get the birch ply at 30mm thick and certainly 24 / 25mm.  Get the supplier to cut the sheets down to your required widths.  The whole sheets are almost too heavy to pick up unless you are @nod's wife who can run up a ladder with one under each arm.

[Tom]

Thanks both. The openings will have a depth of 215mm, as the blocks are being laid on their flats, and will be fair-faced/painted (no render). I can screw a 25mm x 215mm carcassing timber to the hinge side of the opening then put ply over this and on the header and opposite side/vertical. This would mean the timber would have a thickness of 25mm + 18mm + 18mm = 61mm, plus 3mm + 3mm gap = 67mm. Giving myself an additional 10mm each side to allow for adjustment/packing gets to pretty much 90mm. Does this sound reasonable? Do I need "carcassing" all round or would the 18mm ply be sufficient on the header and one side? Is 10mm all round for packing overly generous?

[Mr Punter]

The blockwork will need to be spot on.  If you went for the chunky ply you could omit the architrave and have the exposed edge and a 15mm shadow gap and recess some Compriband or similar in there.

[markc]

Fair faced blockwork …. Brave soul and yes it will need to be spot on. Rules out packings so you are going to have to make up some door frames to correct dimensions, secure in place, plumbed both ways and then they can block tight to frame. make sure fake frame is solid so the verticals do not bow inwards or fitting the doors will be a PITA job

[Tom]

1 hour ago, Mr Punter said:

The blockwork will need to be spot on.  If you went for the chunky ply you could omit the architrave and have the exposed edge and a 15mm shadow gap and recess some Compriband or similar in there.

 

Like the idea but would need architrave to cover the carcassing timber on the hinge side of the opening - assuming 18mnm ply not thick enough on it's own? I was planning on glueing strips of ply to the outside edge of the ply linings to cover the junction with the carcass/blocks, in essence making the lining look like even thicker ply.

 

45 minutes ago, markc said:

Fair faced blockwork …. Brave soul and yes it will need to be spot on. Rules out packings so you are going to have to make up some door frames to correct dimensions, secure in place, plumbed both ways and then they can block tight to frame. make sure fake frame is solid so the verticals do not bow inwards or fitting the doors will be a PITA job

As above, some margin for error if I add ply strips for architrave I guess. The blocklayer comes highly recommended so I hope he can make the opening accurately without frames to work to.

[Mr Punter]

My idea is to use 25mm or 30mm ply.  Build the openings allowing a 10mm-15mm gap to the sides and top of the ply lining.  Install the lining after brickwork, carefully and solidly packing nom 15mm.  Fill the gap with Compriband after decorating, set back 10mm.

 

What lintels do you propose?  Is suggest 100mm x 215mm fair faced.  You really need to avoid little cuts and coursing blocks.

[Tom]

38 minutes ago, Mr Punter said:

My idea is to use 25mm or 30mm ply.  Build the openings allowing a 10mm-15mm gap to the sides and top of the ply lining.  Install the lining after brickwork, carefully and solidly packing nom 15mm.  Fill the gap with Compriband after decorating, set back 10mm.

 

What lintels do you propose?  Is suggest 100mm x 215mm fair faced.  You really need to avoid little cuts and coursing blocks.

 

I think probably 2x narrower lintels for ease of getting them in position.

I don't quite follow your idea for the linings - are you suggesting doing away with the architrave? This would leave 10mm of the compriband visible - not sure re the longevity/practicalities of cleaning, dust collecting etc - though I do like the idea of deleting the architrave, cleaner look to it.

[Mr Punter]

5 minutes ago, Tom said:

are you suggesting doing away with the architrave?

 

Yes.  The compriband will fill the gap between the ply and the blockwork.  If you set it back 10mm it will make a neat shadow gap.  Can be vacuumed but it does not get dusty.