Timber frames

[bristolben]

Hi - I’m considering altering the conservatory by taking off polycarbonate roof and glazing, and replacing it with a timber frame, lightweight roof and finishing with cement board and render.

We’d like to take the external dwarf wall skin to DPC and build off that.

How does one secure the timber plate on the DPC securely? It seems ties won’t work?

 

[Notch7]

Why don't you leave the external brick skin, Fix vertical 50 x 25 battens and attach the rendaboard to that.

I'm not removing the external skin and leaving the internal blockwork is a great idea - you would be better removing it all and do it entirely timber frame.

You can get timber frame to blockwork wall ties, but I have a feeling the risk of displacing the blocks and cracking the plaster is high.

 

[^woody^]

Expansive bolts or screws are fine through the DPC (a blob of silicone is optional). The frame does not need to be held down, just secure from sliding sideways, so the fixings don't need to be heavy duty.

 

[bristolben]

Thanks both - really helpful. Will look into bolts / ties.

We want to leave inside skin as conservatory floor is recently completely finished and has underfloor heating in it - also has power and has been skimmed and painted.

Idea of removing outside skin is to properly insulate the currently un-insulated cavity in the dwarf wall and also I’d need to chip render off that before rendering the whole lot anyway...so just taking it down seems to make sense and leave a better starting point for new render.

 

[Notch7]

Thanks both - really helpful. Will look into bolts / ties.

We want to leave inside skin as conservatory floor is recently completely finished and has underfloor heating in it - also has power and has been skimmed and painted.

Idea of removing outside skin is to properly insulate the currently un-insulated cavity in the dwarf wall and also I’d need to chip render off that before rendering the whole lot anyway...so just taking it down seems to make sense and leave a better starting point for new render.

Ah ok, you just need to be careful to avoid cracking.

I think you will find cement boards for rendering need a cavity behind them rather like timber cladding.

Usually from inside it's: studwork, breathable membrane, 50 x 25 battens, cement board.

The cement boards need to be further out than the brickwork and extend down a bit, so it acts as a drip.

 

[bristolben]

Maybe I’ve misunderstood - but I’d planned the following...

Use the inside skin to build off (without taking down to DPC) and create a stud wall using plasterboard. Use the outside skin to build off (starting at DPC) and cement board the outside of that. That will keep the cavity and also allow an airflow. 100mm celotex in there and we’re good?

 

[Notch7]

Maybe I’ve misunderstood - but I’d planned the following...

Use the inside skin to build off (without taking down to DPC) and create a stud wall using plasterboard. Use the outside skin to build off (starting at DPC) and cement board the outside of that. That will keep the cavity and also allow an airflow. 100mm celotex in there and we’re good?

A ventilated air cavity behind the board is the recommended construction detail for cement fibre boards generally

https://source.thenbs.com/literatur...mNy2GHyvjpvuXTXaQnjHNG/mNy2GHyvjpvuXTXaQnjHNG

that way any cracks in the rendering / board allowing moisture through or condensation forming behind the board -just runs down the air cavity and out.

If you are insulation between the studwork, the existing cavity, if kept will be on the warm, dry side -so wont serve a purpose