Driveway too close to dpc

This damp house · Post by **This damp house** » Thu Sep 02, 2021 5:56 pm

Hi,
I had a new paved driveway, path and patio laid a couple of years ago. I did not know the paving should be a minimum of 150mm below the dpc. Unfortunately mine isn't. I buried my head in the sand for a long while and have just come to the realisation I need to sort my home out before it goes to rack and ruin! Before work began, I had to remove render from the bottom 5 rows of brick work, one of the rows was below the dpc. I guess this is what is meant by bridging. I didn't know at the time, I only removed it because it felt loose and was falling off in places! This pulled out mortar and faces off of bricks. I now have damp problems inside. One job at a time is how I'm planning on sorting this out and I'm wondering how is best to start with this. The slate dpc, or what is left of it is only centimetres below the dpc. Please see attached photos.

Neelix · Post by **Neelix** » Thu Sep 02, 2021 8:52 pm

You need a gully between the house and the patio patio …….who ever laid that doesn’t know what they are doing

This damp house · Post by **This damp house** » Fri Sep 03, 2021 4:56 am

Thanks for replying @Neelix. When you say gully, do you mean a drain channel? (Please see attached image). Do I sit this gully level with the top of the pavers or lower it down as it is so close to the dpc?
Thanks again.

wes56 · Post by **wes56** » Wed Sep 08, 2021 9:31 am

In the past your walls were drilled for injecting so called DPC chemicals.
I think i can see your DPC above the patio - but can you mark where your DPC actually is?
Your walls look to be solid wall - is that right?
Anyway your pointing needs raking out to about 20mm or so and pointed with lime mortar.
Is the inside floor solid or suspended?

This damp house · Post by **This damp house** » Sun Sep 12, 2021 6:13 am

Thanks for replying @wes56.
The walls have actually been injected twice. The first time it was done, the lower part of the wall was rendered over. The second time was whilst it was rendered and they drilled just above it.
I wish the walls were solid! The lower section actually comes out the wall an inch giving a 2" cavity, whilst the rest is a 1" cavity filled with expanding foam. The floor is a solid concrete pad.

wes56 · Post by **wes56** » Sun Sep 12, 2021 8:18 pm

The DPC seems to be a modern plastic DPC? Is it original or inserted later as a remedial repair? Make sure the pointing on the outside of the DPC beds is not bridging the DPC.
The present attempt at pointing is actually a liability, it has to go.

You could remove a few brick from the outside (above the DPC) and see if the cavity is bridging the dpc with bottom fill cavity rubble? You can do this with great care if the CWI is beads.
At the same time check the CWI to see that its not soaked, and allowing penetrating damp to cross the cavity.

Does the interior slab have a membrane ( a DPM)? What relationship does the FFL have to outside ground level, and plastic DPC level?

This damp house · Post by **This damp house** » Mon Sep 13, 2021 3:36 pm

To be honest th dpc is original, it is slate, although very brittle.
I have remove a couple of loose bricks and the expanding foam is higher than the dpc. There is Ash below the dpc but not near it. The mortar used was an Ash based, or so I've been told.
What does ffl mean? I can't tell if the concrete pad has a dpm but it does look close to the dpc level. I guess it could be bridged by that. It was only on Saturday I watched a video on YouTube on that aswell.!

wes56 · Post by **wes56** » Tue Sep 14, 2021 9:23 am

Boy! That slate DPC must have been bending up and down under historic pressure.
Cavity walls are built with two skins and each skin has its own DPC.
Because there's a cavity then injecting a chemical DPC in the outer skin is irrelevant to any rising damp on the inner skin - which is where any rising damp presents itself inside the house.
Penetrating damp, roughly speaking, is damp that has crossed the cavity from the outside skin, and shows on the inside wall.

Why dont you show/pic any damp damage to internal decorations? Which walls have damp damage?
Look behind skirting to try and find any slab membrane.
Are all the floors solid?

This damp house · Post by **This damp house** » Wed Sep 15, 2021 5:26 pm

Slate is very brittle, but being 100 years old i guess it lasted well!
All the affected areas are upto half a metre above skirting boards. Both skins have been injected twice. Damp surveyor has come around today and said I have rising damp. The slate dpc has failed and also the first injection. The second injection must have been installed incorrectly as its only 8 years old and we had these issues pretty much straight away.
I've had the skirting board off and the plaster doesn't touch the ground and the floor is all concrete but can't see any membrane poking out. It is bone dry too.

wes56 · Post by **wes56** » Wed Sep 15, 2021 8:14 pm

The photos are great but I've no way of knowing where they reference with the earlier photos.
After two go's at drilling and injecting two failed DPC's maybe try something else.,
Like lots of others, I've not got much confidence in DPC injections of any kind so you could hack off the plaster and then do it back up with render not plaster. Hack off to about one metre high.
On the outside wall you could do a local area of pointing as well?
The angle bead on the outside corner is rusting and will need replacing with a plastic angle bead.
I've just noticed the last pic of a board pulling away but i cant tell where it is or whats going on ?

This damp house · Post by **This damp house** » Thu Sep 16, 2021 5:01 am

The first photo is behind my front door. It is an interior wall (brick) but joined to the exterior wall.

The second photo is in my kitchen and is an exterior wall. It is behind the wall that I circled further up in this thread.

The third photo is the chimney breast in my dining room. It is lining paper that has started lifting and won't stick back no matter how many times I try.

The more I read up on damp proofing the more weary I'm becoming with regards to the amount of scams out there. I don't really want to keep drilling holes in my walls if I dont have to.

Does the render, plaster or mortar have to be a special kind or just the normal stuff from a hardware store. I hear so much about lime I don't know where to start.

wes56 · Post by **wes56** » Thu Sep 16, 2021 8:42 am

Amen to your comment that anything Damp and Timber seems to be a scam - its an outrage for the last 60yrs so i believe.
There's a strange guy called Peter Ward who seems to be half nuts but still has good criticism of the whole D&T scam. He's on utub and has a web site.
Sand and lime render can be ordinary NH lime and sharp sand (or even any sand) mixed at 3:1 S&L. You mix it yourself.

You could always contact an Independant D&T Surveyor (but some of them are also corrupt) to inspect your property. Guestimate cost £250 to £500.
Its really too much to give you good advice in a forum given the extent of the damage you've mentioned. You need someone on site.

Chimney breasts are well known for having salts from the soot in the flues leaking on to the decorated chimney breast surface. Flues need sweeping and ventilating and contaminated surface plaster hacking off & being replaced by render.

This damp house · Post by **This damp house** » Fri Sep 17, 2021 3:41 pm

I like watching Peter Wards videos. There seems to be a long time battle between him and the damp "wallys"

I like the idea of ventilation and breathability so to speak.
I've found an independent/unbiased damp surveyor who uses many different tools including thermal imaging to identify the problem and how to remedy it for £395. I like the idea of them using something more than a damp meter!
I will have to look into a chimney sweeper as I've never had the chimney swept before.