Renderboard on timber frame, DPC/Tray above window head

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dogman

dogman

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I am looking for some professional advice (if possible)
I am starting a self build that is a passive timber frame which is counter battened and then clad with a cement based render board similar to Knauf Aquapanel and then a thin coat render( not part of this question yet)
A question about how the cavity between the cement board and frame has been asked that i cannot find a answer on any of the manufacturers pages.
The issue is if you need a dpc and weep holes above windows on this sort of build.

Renderboard on timber frame, DPC/Tray above window head
Knauf shown above does not show or mention one. The cavity will be vented at the bottom and top of the wall as normal
 
Staple 175mm dpc under the aperture opening then sail it over the face of the timer and up under the breather membrain.
Staple then tape over
If you can dpc around all opens before windows go in.if not butt it against frames and silicone before boarding reveals to stop and damp getting it
This how we do it.ive been doing it today actually!![emoji106]IMG]https://uploads.tapatalk-cdn.com/20170227/6ff954a830f4400098350bafcc461c20.jpg[/IMG]


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Thanks orangemachineman. Do you put any weep vents in and if yes how.
Your detail is similar to the timber frame manufacturer except they just wrap it over the first batten and not lapped into the breather membrane.
 
dogman said:
I am looking for some professional advice (if possible)
I am starting a self build that is a passive timber frame which is counter battened and then clad with a cement based render board similar to Knauf Aquapanel and then a thin coat render( not part of this question yet)
A question about how the cavity between the cement board and frame has been asked that i cannot find a answer on any of the manufacturers pages.
The issue is if you need a dpc and weep holes above windows on this sort of build.

View attachment 16483
Knauf shown above does not show or mention one. The cavity will be vented at the bottom and top of the wall as normal
Click to expand...
What you mean by dpc?
You have your tyvek returned under the lintel as such and you have a cavity closer batten which is only on the perimeter of the window so your vents on top and soleplate will function as the vent. Don't think you need anymore, but @Runswithscissors can advise you in detail as he's the rep at knauf for the aquapanel products.
 
dogman said:
Thanks orangemachineman. Do you put any weep vents in and if yes how.
Your detail is similar to the timber frame manufacturer except they just wrap it over the first batten and not lapped into the breather membrane.
Click to expand...

No need for weep vents.they are for concrete block substrate
Yes mine is tucked up tight under the bottom of the batten.
Any moisture will be dried out by the air from the vent.


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Zolco, what you are saying is what I have been told. However it was pointed at the TRADA specification, where you flash from the timber frame (lapped under breather membrane) and them out over the drip strip usually a metal profile when using timber weatherboard.
As cement board and then a render seals the structure I have been told its not needed. Its just I cannot find anything definitive.
 
dogman said:
Zolco, what you are saying is what I have been told. However it was pointed at the TRADA specification, where you flash from the timber frame (lapped under breather membrane) and them out over the drip strip usually a metal profile when using timber weatherboard.
As cement board and then a render seals the structure I have been told its not needed. Its just I cannot find anything definitive.
Click to expand...
Yes but you talking 2 different materials there so fitting instructions will be different. Just listen to orangemachineman, he's doing this day in day out
 
Not really decided yet. Wife picked a colour out of the K-rend swatch although does not mean we will use it.
Currently waiting for quotes back but very few we contacted have experience with the systems
I don't know that much about the different systems and some of the web sites are confusing(parex for instance)
 
Thank you, ill try tomorrow. We have found that due to the massive amount of house building in Berkshire and Oxfordshire its hard to find good tradesmen. Most are booked up for months
 
Each spec differs from the manufactures.
Parex spec a roll on tape which goes over the apertures after boarding.


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Last edited:
dogman said:
I am looking for some professional advice (if possible)
I am starting a self build that is a passive timber frame which is counter battened and then clad with a cement based render board similar to Knauf Aquapanel and then a thin coat render( not part of this question yet)
A question about how the cavity between the cement board and frame has been asked that i cannot find a answer on any of the manufacturers pages.
The issue is if you need a dpc and weep holes above windows on this sort of build.

View attachment 16483
Knauf shown above does not show or mention one. The cavity will be vented at the bottom and top of the wall as normal
Click to expand...

Hi Dogman

I am Richard Lord. I am the Knauf Aquapanel Technical Manager

You make some very good and commonly asked questions.

There are various types of directly applied render carrier boards on the market, some have a build up that means the battens need to have a DPC applied prior to fixing the boards. Knauf Aquapanel Exterior is a completely non organic board, therefore there is no need for the DPC, but if for air-tightness you want to wrap the window and door reveals, as well as service penetrations, you can

There is no real need to vent above and below a window on house builds, it is more common on large commercial projects with huge expanses of Façade, to vent larger areas. Again, if you want to, you can... but it is not necessary.

Weep holes are for materials that are solid and will not allow water or moisture to seep through, such as bricks and solid cladding. Boarded render will allow sitting water (if it forms) to seep through. If built correctly, moisture will form in the cavity, but will flow out with airflow, or in colder conditions drain down the back of the board, so actual water should not be there. We have a separate detail that shows the battening around a window, to not crest dead air spaces, happy to assist further and explain if needed.

Please feel free to contact me, or send details through for us to review, comment and assist.

Richard Lord
Knauf
Rlord@knauf.co.uk
07918766577
 
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I did ring three manufacturers today to get a list of their approved contractors. K-rend, Prorend, Parex.
All their "technical staff" were busy so left details and still waiting.
Prorend at least gave me a name to chase if i did not hear anything.
Thanks to @Runswithscissors I will send you an email
 
dogman said:
I did ring three manufacturers today to get a list of their approved contractors. K-rend, Prorend, Parex.
All their "technical staff" were busy so left details and still waiting.
Prorend at least gave me a name to chase if i did not hear anything.
Thanks to @Runswithscissors I will send you an email
Click to expand...
Try them on LinkedIn or Twitter might be bit quicker
 
dogman said:
I did ring three manufacturers today to get a list of their approved contractors. K-rend, Prorend, Parex.
All their "technical staff" were busy so left details and still waiting.
Prorend at least gave me a name to chase if i did not hear anything.
Thanks to @Runswithscissors I will send you an email
Click to expand...

To be fair prorend are very good.
I'm using them on a few big jobs at the minute.
They will get a spec to me in a couple of hours!!
Get parex on the case I would as there will be a few guys up that way


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