Knocking through Wimpey no fines (in situ concrete) house?.

[Bodgitnscarper]

Firstly, hello everyone. I am new to the forum.

I am about to embark upon a self build extension project, although not really "self build" as it is my other half's dad who is to be doing most of the work having been a bricky for such as Redrow etc up until he "semi retired" a few years ago.

I'm not going to teach my grandmother to suck eggs but for those of you who are unfamiliar...

The house is a Wimpey no fines which was built using shuttering and poured in situ concrete, which consists of only concrete and aggregate with no sand (hence the name no fines).
So the walls are basically a solid mass of grey concrete full of pebbles like a giant rice crispies cake!

Does anyone have any experience of knocking through on this type of non standard construction?

Part of the extension is to fit a UB and remove the outside kitchen wall (approx 3.4 metres).

As it is a solid mass, would it still be necessary to use strongboys/acrow props at the back of the house or will the mass of concrete be stable enough to just support the ceiling on the inside whilst cutting a slot and fitting the beam?
Not sure if it makes a difference but the joists run parallel to the wall in question and one side of the kitchen is the gable wall, the other is a supporting wall between the kitchen and living room where the joists from both rooms overlap said supporting wall.

Any advice appreciated.

 

[^woody^]

You'll most likely need a structural engineer to advise if you can do what you what to do.

What you can do and how you can do it is different with no-fines

 

[tony1851]

 

[garyo]

So since it's a Sunday night and my curiosity has been poked... Given that cement is expensive and sand cheap, why would someone build houses with only cement and pebbles?

 

[tony1851]

It's a lot lighter; it pours better in the formwork; probably dries out quicker; probably a better insulator; easier to render etc

 

[Bodgitnscarper]

So since it's a Sunday night and my curiosity has been poked... Given that cement is expensive and sand cheap, why would someone build houses with only cement and pebbles?

Apparently this was a quick way to build houses after the war they erected wooden shuttering and poured the no fines concrete in situ.
It was thought that by using the larger aggregate they would use less concrete and create voids of air between the aggregate.
This, at the time, was supposedly a good idea as the trapped air pockets were supposed to aid with thermal insulation.
However, in practise this did not turn out to be the case. Although slightly better than a solid block of concrete, the thermal properties of these houses are inferior to traditional built types.
Many of these type of houses are retrofitted with external wall insulation (EWI).
Our planned extension is a two storey rear & side with front porch area so most of our external wall area will be to today's standards. The remaining area will have EWI applied before rendering the whole house.

 

[Harmonylee]

We’re currently embarking on our own Wimpey No Fines journey. How did you get on? What headaches did you encounter? We’re looking to do a similar extension!

 

[Nige F]

.