Rising damp

[vic_house]

We moved into a Victorian terraced house, which has a poured concrete floor instead of it's original timber floor. There was no sign of damp when we moved in, so we didn't think too much about this, although our level 3 survey did say that we should lower the ground level. We then had what looked like rising damp, and had a damp survey completed which says we need to remove skirting and cut back plaster to stop bridging. We're fairly confident we can do this ourselves (we have no DIY experience at all but it seems simple).

We aren't sure whether we have a DPC as the surveyor couldn't tell due to this concrete at the front.

Our main issue is how to go about lowering the ground level at the front and back of the house. What time of tradesperson would be able to do this, to make sure they do it to the right level to reduce damp but also not damage the structure of the house?
And, would you also remove the concrete at the front and back of house?

None of our neighbours have damp issues even though some of them have a higher ground level than us. However, we seem to be the only people with a concrete floor so we think this must be the issue. We can't afford to replace the floor with wood, so we're looking for ways to manage the damp.

Would you also suggest using breathable plaster on the internal walls to further reduce damp?

Thank you!!

 

[Cubist]

A couple of quick questions first;

• Am I right in thinking the wall which includes what may be chimney breast is a party wall shared with your neighbour?
• The masonry layout on the front elevation suggest this house had/has a cellar. Can you confirm?
• When was the house built? A date will confirm whether a DPC would have been likely.

The first jobs must be to cut back the render to the rear of the property as this may be bridging any DPC that may have been installed when the house was built.

The height of the garden and paved area to the front of the house must be reduced to the equivalent of roughly two courses of brickwork below the bottom edge of the door cill shown.

Breathable lime plasters will offer no advantage for the party walls but may for those with an exterior elevation.

You may need to cut back the concrete at the front and back of the house but not necessarily all of it. It may be sufficient to remove say the first 0.5 metre only from the walls.

 

[vic_house]

Yes the side with the chimney breast is a party wall. They've got suspended timber floor, and they have no damp issues. We have damp on both sides of the house (we're a very narrow house so it's on all of the walls both sides of the house).

We've got no cellar.

It was built in 1860s, and so the surveyor says it's likely there'd be no DPC as it's unlikely they'd have placed one under the concrete floor when they did it.

When you cut back the render at the back of the house, would you also lower the ground level? The survey and damp survey indicated that both the front and back of the house have a ground level which is too high, but ours is lower than, or the same height as, all of our neighbours levels (along the same terrace). We're unsure how low it should be made seeing as we have a concrete floor and likely no DPC.

When you reduce the level of the garden at the front, would you then fill the trench in with another material to make it look the same height as the front of the house?

 

[Cubist]

The reason I asked whether it was a party wall was that it bears clear evidence of rising damp BUT I also noted that your neighbours claim to have none but they still have suspended wooden floors in their homes! This, to my mind, can only be explained by the presence of a DPM beneath your concrete floors which is causing damp rising from the earth to be pushed outward toward all the interior walls after it meets the underside of the DPM. If you raise a corner or two of any carpeting do you detect any dampness of the concrete or the carpet underlay? If any such damp is not restricted to the edges nearest the walls then that would confirm my suspicion to be false. If you were to remove a short length of any skirting boards around the perimeter of the room you may find the edge of the DPM just below its bottom edge or even trapped behind it.

1860 pre-dates the adoption of DPC standards for new builds in the UK but that does not mean one was not included in your home. When you begin reducing the height of the land outside you should keep your eyes open for the remains of any old and now filled air-bricks in the walls. These may/would have been used to ensure the underfloor voids were effectively ventilated to prevent rot and if found would provide a clue to the presence and location of any kind of DPC - at that time beds of poured pitch/tar or slate tiles may have been used. The front or rear elevations of your neighbours homes having suspended wooden floors may also confirm whether air-bricks were used. Typically a DPC, if present, would appear one or two brick course below such.

I'm surprised theres no cellar - the brickwork pattern below the window suggests the kind of supporting structure needed above say a coal chute.

When you cut back the render at the back of the house, would you also lower the ground level?

Yes, if at all possible.

When you reduce the level of the garden at the front, would you then fill the trench in with another material to make it look the same height as the front of the house?

I would be tempted to leave the masonry exposed for a year or so to see if theres any appreciable reduction of damp penetration to the indoors. It could be that leaving this area exposed, if I'm right about the DPM, could be your only viable route to reducing the indoor problem.

 

[a twig]

You may also get lucky when cutting back the render and find a DPC like wot I did. You may find my thread on my current property relevant

A

Thread 'Hotel Dampifornia'

Aug 12, 2023

You can check out but you’ll never leave!

So, sadly had to sell our forever home in Somerset - moved to a newer house supposedly with no problems. Didn’t bother with a survey as have got bored of paying for ever more inventive works of fiction and so moved in to inevitably find daaaamp in the old section of the house that dates back to 1860…

The previous owners were kind enough to share the survey they had done when they purchased which said there was no DPC in the original building and also there was no asbestos anywhere in the building.

Having found asbestos in the building not long...

• a twig
• Replies: 30
• Forum: Projects

• 

 

[stuart45]

If there's a DPM under the concrete floor, it could cause some damp issues in the walls. It used to sometimes on new builds on the 70's when it wasn't lapped into the DPC.

 

[montyjohn]

What temperature are you keeping your house at.
If it's cold <15 degrees with a high relative humidity it could just be condensation as the lower part of your wall will be coldest and so it condenses here first.

If it was rising damp I expect to see more salts and plaster damage. It looks like condensation.