Rising damp treatment, external render, plinth and DPC advice

[madeinstein]

Hi,

I'm trying to get an advice what is the best approach to replacing old render plinth & external wall render after damp proofing (this is old house btw), there seems to be a lot of opinions of render bridging the DPC etc.

The way I understand it so far on the brick only wall it's quite straight forward, you put DPC layer around 15cm above ground level and plinth is underneath that - should not bridge DPC.

But what do you do on the wall where bricks are covered with render? Is it correct to put plinth render to the level of DPC then install Bellcast Bead on top of that and put wall rendering on from the DPC lever and above? (Pretty much what is done on this youtube video or is there a better way?

Also the DPC level should be 15cm above the external ground level and below the internal wood floor as seen on this youtube video

which is pretty much impossible as the wood floor is on the same level as outside ground - any advice here? Is it better to put the DPC lower and cover with plinth or keep it at 15cm and install something (damp proof membrane?) inside up to the level of DPC? Or have second internal DPC level lower just above floor?

Lastly after removing old plaster inside is it enough to put a new one with render additive (Renderguard Gold) or is it better to treat the wall with some kinds of Cream (Dryshield Cream) before rendering?

If you can point me to any information online I would be grateful as I couldn't find much apart from couple you tube videos.

Thanks

 

[ree]

Its best on a DIY forum to describe not prescribe - show us whats there and we might be able to help.

Pics of inside and outside the house would help. FWIW: the first pic you show is wrong.

Can you scan a sketched section view(s) of the low floor and outside ground level and the position of any DPC?

Are all the floors suspended?
Are the walls solid or cavity?

Best practice is to remove plinths not install them.

 

[madeinstein]

Hi, thanks.. this is the best pic I have of outside wall at the moment.

Sidewall

• madeinstein
• 24 Jul 2015

it's a solid wall and floor is suspended. The floor level is just above the ground level.

I tried to remove the concrete render but it's almost impossible as it's rock solid and I would just destroy all the bricks under.

So I'm trying to find out where to put DPC layer knowing that the outside render (or plinth) has to go all the way to the ground level and how to isolate render/plinth so it doesn't bridge DPC layer.

 

[ree]

Your outside GL has been raised by the flags. Damp, degraded render can be seen at the wall base. I dont see a plinth? More pics please.

Where is the existing DPC?

How do you propose to insert a new DPC in your solid wall? Dont even attempt it.

Have you carefully examined the walls (all your walls) at low level inside and outside for signs of damp? Check skirtings and any wallpaper.
Have you examined under the floors for fungal damage to the joists or flooring?

A typical method of dealing with your situation is to cut a trench by the wall and fill with chippings - or install a French drain.

A small breaker can be hired and it will remove the render. Sand and cement not concrete.

There's masses of info on here about all the above. FWIW: if you care to read some of my back posts on precisely these issues it might help. Look below at similar issues.

 

[madeinstein]

Just answering couple of your questions

I dont see a plinth?

There is no plinth currently, I was asking if there should be going forward.


Have you carefully examined the walls..

Yes we have rising damp on the inside wall and this is the reason I'm doing it.


How do you propose to insert a new DPC in your solid wall? Dont even attempt it.

From inside


So what's your recommendation regarding outside wall?

Remove render at the bottom to the level of new DPC? What then? As I mentioned before brick wall will be too damaged to leave it uncovered. The only thing I've seen so far is what's on the first video. Plinth to the level of DPC then barrier than render.

Re French Drain I guess this is in addition to the work above - thanks for pointing that.

By Solid wall I mean this, the outside render is less that 1inch thick.

 

[ree]

There are a few questions still outstanding?

The wall is solid as in the lower pic?

Injecting DryZone might do a bit of good then again it might not: by and large, injected DPC's are worthless - removing any interior salt damaged plaster and rendering back with sand and lime and a remedial skim will give you say 20 yrs of clean decorated wall surface.

 

[madeinstein]

Yes it's solid as on the lower pic.

So this is my current plan

• put DryRod (like DryZone but solid) into the wall
• re-plaster from inside with Thistle DriCoat (http://www.british-gypsum.com/products/thistle-dricoat) - found it on another forum.
• Treat the bottom of the inside wall with DryBase (below DPC)

The priority is to fix the wall inside as it's unhealthy in it's current state. It's a 100y old English house so it's not easy to find a perfect solution and as you said DPC might or might not work at the end but it's the best/cheapest shot I have.

I'm still not sure what to do with outside rendered wall (original question), any help/recommendation appreciated.