Garden Wall help please!?

[andybag]

We are building small garden walls to use as raised beds for planting. The footings have already been done (150mm deep concrete) and i'm going to use the lightweight Celcon Blocks. I'm only going 2 blocks high for most of it then 3 blocks in the corner. There are 2 walls 600mm apart running parallel. We want to render / paint the walls white when complete

Now my questions:

1. Do I need to lay a course of bricks as a DPC below the blocks to render down to?
2. can I use standard facing bricks to do this if so?
3. Realistically, how difficult is it to render blocks and should i bite the bullet and employ a plasterer to do the job properly the first time?

Hope someone can shed some lighton my questions..

Thanks

Andy

 

[^woody^]

A DPC is a waste of time in a raised bed. If you use bricks then they need to be engineering class or at least have a high frost resistance rating - not all standard facings have this

Aerated blocks are the wrong choice for this as they quickly suffer from frost damage and crumble, and their compostiton alows for enough thermal movement to crack render in this use

Rendering a raised bed is problematic, as the wall will stay damp from the soil behind it and this blows the render off the front.

If you are rendering then you should use a concrete block and coat the back with a waterproof compound such as RIW or Marley Superprufe

If you have never rendered before, then you are unlikley to get a flat surface, and probably morte like some mediteranian stucco effect. If you want it flat, then someone experienced would be the obvious choice

Use appropriate copings to keep water off the top of the wall, or prevent it entering the wall via the top

 

[RonnyRaygun]

Not really my area of expertise but as no-one else has posted...

Firstly, no need for a dpc in a garden wall...good practice to use engineering brick below ground but as your flower bed will presumably come up to the full height of the wall on one side, so there will be a source of moisture to full height of the wall.

In any case, facing bricks would be the worst thing you could use below ground.

I wouldn't use Celcon for a garden wall. They soak up water like no-one's business and there is very little key for the render...it would come off in no time in my opinion.

Id either use aggregate blocks and render them or use engineering bricks.

 

[RonnyRaygun]

Beat me to it Woody

 

[andybag]

Thanks for your replies.

I've spoke to Celcon and read the spec of the Celcon blocks and they're supposed to be more resistant to water ingress / frost damage than normal blocks.

We're going to line the inside of the walls with protective covering to prevent the damp from that side.

 

[^woody^]

Leave a celcon block in the garden for a few years and see how resistant it is.

They resist cold, and can be in damp underground footings - but they are crap with regards to frost freeze/thaw action.

Celcon are telling you porkies

But then you are left with the other issue of them expanding/contracting more due to varying temperature or dampness - this causes the render to de-bond

 

[andybag]

Thanks Woody. That seems to be the same thinkg i'm hearing from a few people to be honest.

Thanks again for your replies...