Render & extend at the same time?

[nomisr]

Hi,

I'm about to extend both sides and the rear of a detached bungalow under permitted development. I've obtained a CLUP from the local council to cover the works. The PD rules say that any extension should use the same materials as the existing dwelling, where practical. In my case this is Bradstone buff dressed concrete blocks, which are still available in imperial sizes. I've got two problems though.

1. The one and only existing wall that will still be visible is badly weathered and needs to be re-pointed due to some fairly bad settlement cracks.

2. The U-value of Bradstone blocks is pretty bad. I really don't want Thermalite blocks on the inner leaf due to their poor structural properties, and I really don't want the wall thickness to exceed 300mm, so meeting the current Part L regs will be challenging.

I'd rather render the whole lot even though this means improving the thermal performance of the existing wall.

Now, as far as I can tell, I could render the existing dwelling and then build the extensions to match with no problem. I could also build the extensions using Bradstone blocks and then render the whole lot.

But could I get away with building the extensions using regular blocks and then render the whole lot?

Cheers,
Nomis

 

[cjard]

Well, it doesn't say identical, but it does say similar. How similar is render that is painted the same shade as the buff blocks that are there now? Or even render that is through-coloured?

Thermalite is structurally poor? sure wish someone had told me that before I followed the manufacturer's advice and built a 3 storey house on them!

 

[nomisr]

The plan was to render with a sand / cement skim and coat with masonry paint of a similar shade to Bradstone buff. I guess from a distance this wouldn't look so different from what's there now.

Thermalite is fine in compression but I'm used to brick or at least medium density concrete block on the inner leaf. I've heard that screws have a habit of pulling out of Thermalite and now have visions of kitchen cabinets falling off the walls. I also hope to put up some heavyweight shelves in one of the rooms and would like something solid to screw them to. What's your experience been like with Thermalite?

 

[DCzBuild]

what happened in the end, did you render first then build?

 

[JohnD]

 

[cjard]

The plan was to render with a sand / cement skim and coat with masonry paint.

What's your experience been like with Thermalite?

Through coloured render could save you the nuisance of having to paint..

I think you'll be fine with your shelving and cupboards - loads mainly act in a downwards direction from a cupboard that is hung at the top; there isn't much torque even if your heaviest plates are at the front of the shelf. As such you need more shear resistance than pullout resistance and a long concrete screw wound into a suitably sized predrilled hole in thermalise will be fine

Short version; drill a 6mm hole in your thermal and use 120mm concrete screws to secure the batten that will support your cupboards

 

[Nakajo]

@cjard So where's he been keeping his plates for the last 3 years?

 

[cjard]

On the floor. while he desperately awaits a reply on the most venerable of diy sites...