Building Up Over DPC

self builder 123 · 16 May 2009

Hi

We are going to be forming a concrete base for our heating oil tank which will be right against the garage wall.

The base needs to be higher than the DPC in the garage wall and there is little or no room to pull the base out from the garage wall.

We plan to paint the affected area of the garage wall with liquid DPM from the ground level right up past the DPC to the top of the oil tank base.

We also plan to install a couple of layers of DPM from the ground level right up the wall following the liquid DPM.

I have attached a diagram.

Once the concrete base is poured the wall above will be finished with wet harling. At the bottom of the harling will be a bell cast which will through the rain water onto to top of the concrete base.

Will this plan ensure that no water gets into the wall from above or allow any water to rise up and breach the DPC.

Cheers.

Untitled

self builder 123
16 May 2009
2

shark85 · 17 May 2009

Hi there

Yes you will have no problems if you stick to that design

self builder 123 · 17 May 2009

Cheers !

noseall · 19 May 2009

Strictly speaking the most vulnerable part is where water may splash onto the concrete base and against the exposed wall. As it will be rendered then it will be less vulnerable.

Also there is a chance water could wick up the render should any water lie on the base itself.

This is all ifs and buts as a large part of the base will be sheltered by the tank anyhow.

Make sure the base has some kind of fall to deflect any rainwater.

In the unlikely event problems should arise due to splash etc, then i would advise cutting the render back up 150mm above the base surface then fit a lead up-stand, chased into the wall.

But as i said a waterproof render with a bell cast should offer protection. It mat be an idea to keep the bell bead off the tank base an inch or two though.

masona · 19 May 2009

self builder 123 said:
We plan to paint the affected area of the garage wall with liquid DPM from the ground level right up past the DPC to the top of the oil tank base.

Best to go at least 150mm higher to cope with rain splashing, just a thought, maybe a lean to roof to keep the tank dry as well

self builder 123 · 21 May 2009

Hi Noseall & Masona

I forgot to mention that the garage wall is in fact a timber frame construction so there is a 50mm cavity behind the 100mm outer concrete block leaf which is to be wet harled.

I take that this cavity will avoid the issues that you mentioned ?

Cheers

masona · 28 May 2009

Personally, I wouldn't have the tank butted up against the wall as you may get condensation problem, if it was me, I would have 50mm gap for air flow

self builder 123 · 28 May 2009

Hi Masona

There will be a 150mm air gap right around the tank.

self builder 123 · 28 May 2009

Hi Noseall & Masona

I forgot to mention that the garage wall is in fact a timber frame construction so there is a 50mm cavity behind the 100mm outer concrete block leaf which is to be wet harled.

I take that this cavity will avoid the issues that you mentioned ?

Cheers

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Building Up Over DPC

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