I am planning to build a free standing garage out of 150mm thick concrete blocks. 6m x 5m x 2.7m floor to bottom of room. Intend to insulate and render the inside of the garage with 100mm insulation. 

My question is do I need to use piers when using 150mm concrete blocks ? What are the benefits and drawbacks to using 100mm concrete blocks with piers instead of 150mm concrete blocks? Thanks . 

53 minutes ago, Trev1 said:

Intend to insulate and render the inside of the garage

 

Hello @Trev1 Is the above a typo? If not what are you going to do about the outside of the garage?

 

I’m currently building one (very slowly) with 100mm blocks and then external insulation that will be rendered. The 6-7m wall lengths required some kind of bracing, we went for windposts. 

15 hours ago, Trev1 said:

I am planning to build a free standing garage out of 150mm thick concrete blocks. 6m x 5m x 2.7m floor to bottom of room. Intend to insulate and render the inside of the garage with 100mm insulation. 

My question is do I need to use piers when using 150mm concrete blocks ? What are the benefits and drawbacks to using 100mm concrete blocks with piers instead of 150mm concrete blocks? Thanks . 

You could try 150mm hollow blocks with rebar from the footing and concrete filled, but only an SE could prove the design, taking into account location, elevation and roof span and structure, the same goes for 100mm block and piers.

The height is the issue here. Part A building regulations says wall below 2.5m can be 90mm but with piers.

 

So reverting to the general rules H/16 = 2.7/16 = 170mm thickness.

This is where you get a bit stuck. You have the general regs that are conservative and for good reason. 

 

There is a balance to be struck.. do you pay an SE to refine the design or stick to the often conservative regs?

 

On the face of it stick in some piers if you can live with that.

 

As an aside concrete blocks are normally 140mm (actual size) thick rather than 150 thick (nominal 6")

On 05/04/2024 at 22:09, Trev1 said:

Intend to insulate and render the inside of the garage with 100mm insulation. 

Be careful with the detailing here.. are you going to put the insulation on the outside or inside?

 

Best to post a detail of what you are intending and you'll get lots of good advice.

 

 

 

With 100mm insulation and 150mm blocks you're at 250mm.

 

Why not just build a full fill cavity wall with batt insulation? 

 

Alternatively a TF garage with an insulated inner stud and block external leaf.