Dwarf wall DPC dilema !

[f1hydro]

Hi All

I'm about to embark on a selfbuild conservatory and have a couple of questions relating to the dwarf wall and DPC's

Dwarf wall spec is as follows; 450 x 225 footing, 1 course of trench blocks, 2 courses of brick work (2 skins with 50mm cavity) This brings me up to exisiting house DPC level. 600mm wall on top of this.

I have 2 options for the vertical joints adjoining the house, either 'tooth' the dwarf wall in, in which case could I avoid using a vertical cavitray by opening up the cavity in the house wall and continue it into the dwarf wall ?
Or use a vertical cavitray and tie the dwarf wall to the house wall. Not sure which is the best option ?

I have a similar dilema concerning the opening for the french doors into the garden. Is it better to use a vertical cavicloser between the 2 skins or return the brickwork and use a vertical DPC ?

All help, suggestions welcome

Thanks

Robin

 

[noseall]

I have 2 options for the vertical joints adjoining the house, either 'tooth' the dwarf wall in, in which case could I avoid using a vertical cavitray by opening up the cavity in the house wall and continue it into the dwarf wall ?
Or use a vertical cavitray and tie the dwarf wall to the house wall. Not sure which is the best option ?

Does the dwarf wall hit the existing house wall at 90 degrees or is it in-line with the existing wall? Are the new bricks the same size as the existing.
If it hits the existing at 90 degrees just drill and fix a couple of fish tail ties or bent fish tail frame ties. If it is in-line and the bricks match, then toothing sometimes looks better. Don't worry about dpc detail at this junction, as the same situation occurs above the dwarf wall where the upvc widows meet the wall.

I have a similar dilema concerning the opening for the french doors into the garden. Is it better to use a vertical cavicloser between the 2 skins or return the brickwork and use a vertical DPC ?

Although expensive, cav' closers are a convenient way of finishing the reveal cavity. In the world of regulations, only aerated blocks are permitted to return to the brickwork with a dpc junction.

 

[f1hydro]

Hi Noseall,
first many thanks for the reply.

Does the dwarf wall hit the existing house wall at 90 degrees or is it in-line with the existing wall? Are the new bricks the same size as the existing.
If it hits the existing at 90 degrees just drill and fix a couple of fish tail ties or bent fish tail frame ties. If it is in-line and the bricks match, then toothing sometimes looks better. Don't worry about dpc detail at this junction, as the same situation occurs above the dwarf wall where the upvc widows meet the wall

One end of the wall hits the house inline, the other side will be @ 90 degrees. The bricks will be the same as used in the house. Good point, I hadn't even considered the interface between the upvc units and the house up until this juncture. If I use no DPC in this area, do I not run the risk of penetration behind the upvc frame ?
With this in mind should I run a vertical cavitray from floor to roof height at this joint or is this a bit overkill and I'm worrying about nothing ?

Although expensive, cav' closers are a convenient way of finishing the reveal cavity. In the world of regulations, only aerated blocks are permitted to return to the brickwork with a dpc junction.

Looks like cavicloser is the best option then. This would simplify using a different colour brick on internal and external skins, as I was contemplating leaving the internal skin exposed anyway. Just hope my brickwork skills are up to it

 

[noseall]

Penetrating damp, via wind driven rain, is rare in-land.

I would by no means say it is exclusively a coastal problem, but the fact that local in-land building control bodies, do not enforce retrospectively fitting cavity trays, says it all.

In 27 years of building, i have only seen the need for cavity trays once. There are some that say interstitial condensation can build up within a cavity, but i am not convinced it is a problem.

 

[noseall]

I was contemplating leaving the internal skin exposed anyway. Just hope my brickwork skills are up to it

If this is the case then do as you originally suggested. Return the bricks at the reveal detail and use a vertical dpc.

B'regs do not apply to conservatories, and cold bridging will not be an issue as the whole thing will be cold! Cavity closers are not discreet and are visible the full width of the cavity, so will not be suitable where fair faced brickwork is used on the inner leaf of masonry.

 

[cowboyontheloose]

Just butt to existing .does damp come through the cavity I doubt not, making a Mountain out of a mole hill lol