External render plinth

kregler · Post by **kregler** » Fri Apr 10, 2009 11:00 pm

My 1930's house has a concrete plinth which runs round the property up to about 2ft.

Some of this is starting to come away, or has fallen off. I understand this is a "splashguard" for the lower part of the walls.

How do I go about repairing this?

Thanks in advance.

Post by **ultimatehandyman** » Sun Apr 12, 2009 11:51 am

Some pictures would be good

You could probably patch it up with a mortar mix, or a mortar repair compound. It depends how big of an area it is really.

If it is a large area, then mortar repair compound would work out expensive.

If using mortar, you could also add a waterproofing admix.

dewaltdisney · Post by **dewaltdisney** » Sun Apr 12, 2009 7:03 pm

What happens to these plinth renders in that there is no expansion gap built in. Water gets behind through cracks between the top edge and the wall and a good frost does the rest. Small natural structural movements can also help it on its way.

A batten is fixed to the wall top as a former for the top edge. If you cut an angle on the batten you could form a run off top edge. The mix is rendered on and leveled with a float or a gauge. If the wall is exposed I guess a bead of clear silicone along the top edge and wall may help stop water ingress.

Not sure of the mix ratios

DWD

leebwk · Post by **leebwk** » Tue Apr 14, 2009 11:21 am

I think you are referring to a belcast at DPC level, from experiance ifyour render is breaking down i would chop it off neatly and refix new beads and re-render.

Do you have any pics ?

kregler · Post by **kregler** » Tue Apr 14, 2009 8:21 pm

I'll take some photos tomorrow so you can get a better view of what it is but definately sounds like dewaltdisney has described!!!

theplasterersarms · Post by **theplasterersarms** » Fri Apr 17, 2009 8:46 pm

dewaltdisney wrote:What happens to these plinth renders in that there is no expansion gap built in. Water gets behind through cracks between the top edge and the wall and a good frost does the rest. Small natural structural movements can also help it on its way.

A batten is fixed to the wall top as a former for the top edge. If you cut an angle on the batten you could form a run off top edge. The mix is rendered on and leveled with a float or a gauge. If the wall is exposed I guess a bead of clear silicone along the top edge and wall may help stop water ingress.

Not sure of the mix ratios

DWD

excellent advice but myself personally I would look at a polyurethane instead of a silicon caulk for the exterior