What blocks can I/should I use?

[nickjb]

My single storey kitchen extension will be a block cavity wall. What's the best option for the blocks (especially for a novice)?

Below the dpc is it easier to use 300mm foundation blocks or standard concrete blocks filled with a weak mix? What about the walls? The inner will take the flat roof joists. Can these be lightweight thermal blocks? And the outer wall? It's going to be rendered to match the rest of the house.

 

[stuart45]

When you say best, do you mean cheapest, quality or easiest for you to lay? AAC blocks are light and easy to cut, but can suffer shrinkage cracking.
Maybe use concrete outside and AAC inside.
Foundation blocks are quick and easy.

 

[RonnyRaygun]

When you say best, do you mean cheapest, quality or easiest for you to lay? AAC blocks are light and easy to cut, but can suffer shrinkage cracking.
Maybe use concrete outside and AAC inside.
Foundation blocks are quick and easy.

Another reason for using concrete blocks outside is that they are much easier to render. AAC blocks can be a nightmare to get a decent bond between block and render.

 

[nickjb]

Thanks. Not really sure what I mean by best. Easiest to build a wall with that won't fall down, probably. Foundation, aac inner and standard bocks outer sounds good.

I believe I need some of these to extend the existing house ventilation. Is there a trick to fitting them in foundation blocks of do I just build that area with engineering brick?

 

[stuart45]

You need to use brickwork. What is the floor? eg block and beam.

 

[tony1851]

If the wall is going to be rendered, why not use solid aac blockwork, and line the inside with insulated plasterboard?

 

[nickjb]

What is the floor?

Floor will be a slab. The vents are only to extend from the existing house which has wooden floors and vents.

If the wall is going to be rendered, why not use solid aac blockwork, and line the inside with insulated plasterboard?

I'm not sure? Is it a better system? I noticed the neighbours extension went up with solid blockwork, but it's not something I am familiar with.

Another thing... if it's going to be rendered is there a particular type of pointing or does it not matter?

 

[stuart45]

The only problem with solid AAC blockwork rendered is that if any cracks appear in the render in the future water can leak in and can't escape again too easily.
You don't have to worry about a certain type of pointing, just make sure the joints are full.