render timber frame extension - riblath - advice

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mingmatt

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First post and need some advice.

Timber frame 1st Floor extension, Euroform fire rated racking board wrapped in Tyvec housewrap.

wall 1 : 8m X 3.5m
wall 2 : 5m X 3m
wall 3 : 3.5m X 3m

I have sourced a load of stainless riblath as the walls need rendering to match existing. Existing is a mixture of stippled finish and tyrolean.

Building control states mesh and lath over tyvec although I am using riblath (not eml)

My questions are :

1.Expansion joints for wall 1 (8m X 3.5m) - this wall interfaces with existing brick along bottom and 3m edge. Should an expansion joint go on the interface between the different substrates and also further along the wall (due to large area) ?

2.Internal corner (if that is the correct phrase) between new extension and old brickwork. Should there be mesh between here and just render or two stop beads back to back and filled with a mastic of some sort (or other approach) ?

3.Best approach for fixing and rendering riblath (if I decide to have a stab at this) ?

4.Best mix and coating option for the render ?

5.Mathing existing tyrolean - is it worth the bother / alternative approach ?

I would like to understand the approach to all this as I need to know that whoever does this (be it me or some other lucky chap), it gets done correctly.

Thanks for advice

Emperor MingMatt [ Master of Nothing ]
 
catnic or expamet or similar will have a spec to follow. you will need to make sure youre mixes are absolutely correct even ensuring the sand is of correct quality.
 
seeing that your just at the planning stage it would be far easier to spec lafarge GTEC aquaboards(external grade plasterboards) and just use a thin coat render system on that. Parex have a BBA using these boards for timber frame direct render applications
 
Please do what goody says. I fit this system alot and you cant go wrong. remember your cavity between the subframe and the racking boards whatever you use
 
plasterjfe said:
Please do what goody says. I fit this system alot and you cant go wrong. remember your cavity between the subframe and the racking boards whatever you use
Click to expand...

Would he be as well fixing insulated panels direct to the sheathing , he wouldn't have to worry about venting the cavity then would he, and then a thin coat system , probs work out cheaper than timber/steel frame and renderclad panels
 
nhbc still want cavity Paul, thats why the insulation Rail systems exist - rubbish imo.

the insurance co. always insist on a vented subframe on timber construction case studies proven rotted timbers in the past due to surface contact promoting water ingress and prolonged damp and condensation.
 
or do what the two jam roles did round the corner from my job - render it with S and C straight on the felt:RpS_lol::RpS_lol:
 
Thanks for your responses.

I am stuck with just enough room for render as the wall is on the property border

The boarding that we had to use is fire and water resistant but we put a tyvec membrane on it anyway. I could have got away with just painting the boarding and filling the gaps but it would look a bit industrial. Just need to match to existing house, hence render.

The timber frame cavity is going to be completely filled with 150mm celotex followed by vapour stop membrane and plasterboard on the inside. The membrane stops the interstitial condensation and having the wall effectively solid (fully filled voids) prevents air circulating and condesing on the timbers (if air gets through the vapour barrier). I guess thats why the straw bale thing works ok also - maybe should have gone for that but the rooms would have ended up being smaller.
 
the cavity I speak of mate is not within the frame or internal it is only 20MM on the outer leaf. You counter batten your subframe with somethin like a 25mm batten then screw render board direct to that then apply a 4mm thin coat render to directly to the board. if your dealing with a local council building control for extensions you will prob get away with it cos they aint that clued up on this area
 
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