Best way to fit entrance door in cavity wall

[j_s]

We are likely to get a new entrance door soonish and it'll be an RK door I expect. I'd like to set the door back slightly further in the reveal but I'm not sure on the best way to attach to the wall due to the cavity. Should I consider lining the reveal in ply and screw the door to the ply?

 

We will be cladding the external brickwork in cedar once the door has been fitted so I can add lashings of sealant before we clad up to the door

 

Thanks

James

Edited November 18, 2017 by j_s

[Oz07]

If you fix to external skin your only really limited by how good a fixing you can get. 30mm over brickwork 40mm into cav seems to work ok. Last new build I used a different method for better fixing. Fixed a 2x2 treated batten up the inside face of brickwork, cavity closer thickness back from edge and dpc between timber and brick. This enables you to drop it back more but still get decent fixing. Although with a thinner cavity it might be hard to do. 

[Nickfromwales]

Just ask the door supplier to give you the metal fixing brackets needed to set the door wherever you like whilst still being able to fix into masonry / other. 

As above, if Bco is involved you'll have to install a vertical damp course and insulate the cavity. My preferred method is to get some 18" DPC, wedge it against the face brick with small offcuts of polystyrene spaced every 300mm or so to keep it taught and in place, then fill the gap with low expansion ( LE )  foam, applied to obtain a depth of no greater than 150mm. 

Have the DPC showing in the opening about an inch or so, so that when you fit the cavity closers you can fix over the DPC ensuring no break. The closers are plastic / PVC ( ? ) anyhoo so the damp cannot bridge . 

If you get insulated cavity closers you'll need to trim the factory fitted insulation to suit your cavity ( they're marked for cutting at the correct increments so a 1 minute job with an old hand saw ) but you'll then need to rake out a little of the foam in the cavity to accommodate the extra depth. For good measure, as I've done on my current job ( garage conversion with new knock through of a cavity wall ) I pumped a hefty bead of LE foam into the cavity and set the cavity closer into that. Brace with a piece of batten or 4x2" for 30mins whilst the foam cures to stop the closers from bellying out with the foam as its expands and cures. 

When ordering the door, make sure you allow for 25mm of cellotex to go at the head, bonded to the internal section of the catnic, to eliminate the cold bridge. Catnics are factory insulated but it's still not great. 

[Nickfromwales]

For belt n braces I've lined the reveals with 25mm cellotex too   This job has IWI ( 62.5mm thermal PB ) so I wanted to be double sure there was no significant shift in 'temperature' in the window or door reveals. That just gets PB bonded on then for which I use the foam and bracing to keep it flat whilst it cures. 

 

[j_s]

Thanks guys