How to protect the damp proof layer of external wall
Anonymous user 23/02/2024 - 3.50 PM
Hi we have a new extension built by breeze blocks. We just had it silicone rendered. The renderer did not render the bottom half of the external wall (damp proof layer) as he said it needs to be painted by damp proof paint and gravel put in it so that damp does not get absorbed. I am a bit concerned as I thought you can render till the bottom of the wall. Now I have a border of breeze block exposed to the elements. I thought render protected against damp. Please advice how to protect the bottom half of the wall. Thanks
thanks for your answer , to clarify the breeze block (DPC) is bare and should it be treated with damp proof paint as not rendered or is there a special membrane to cover it and prevent damp. As i have heard gravel around the lower part of external wall absorbs water . Who does damp proofing , a general builder ? or renderer.
Are you a tradesperson and able to answer this question?
Their should of been 2 course of face brick of what could be viewed and then a bel cast bead fitted and then render above that
And you’d should not render to the floor Past the dpc
If it's below ground you need to create a Barrier using an underground membrane. If it's just fairly low level, you can just paint it with exterior paint. If it fairly high eg several steps high, you can render down with a bellcast finish just above the dpc and render up, just under the dpc finished with a stop end bead. You only need a 10-20mm bridging gap. All this is to stop any damp from below the dpc rising up the external render.
Cheers
This is a little complicated. The first thing is that render must always stop just above the dpc. This is because if the dpc is covered, ground moisture will track upwards via the render. For the same reason, render should never go to ground level. It does in many old properties because they did not do it correctly. The wall below the bottom of the render and dpc should be painted with a breathable masonry paint. Gravel is fine so long as it is not higher than the dpc or again, moisture will track upwards. Hope this all helps.
First of all. as in someone else's statement .
Celcons are not really for external walls.
And definitely not below the DPC
As there not load bearing max.3.6N and are not impervious to moisture ..
I would definitely speak with your building inspector and question this.
