Damp in house

[Satkin]

Hi folks.
Some damp issues in a 1950's semi, cavity wall, suspended timber floor property I have just purchased.

Pre purchase survey indicated rising damp, as there was quite a bit of damaged plaster, peeling wallpaper and rotten skirting.

got another company to investigate who said it was absolutely long term condensation issues due to insufficient sub floor ventilation. With some wet rot to a number of joists. So continued with the purchase but at a reduced price.

Since moving in, I have taken some floor boards up to check the subfloor void. Looked pretty dry, but with some patches of damp in corners where very little airflow was getting.
There was also a mountain of dirt down there which I removed back to the concrete oversite.

Since then we have had new airbricks installed, and doubled the amount.

Over the last couple of days with some snowfall and a bit of rain, I noticed that the edges of the subfloor have become wet. (see attached image) and I am really concerned.

What could cause this?

We are wanting to get all the timber and stuff sorted out soon so we can decorate, but don't want the issues to come back if there is water literally coming in to the subfloor.

For reference, the image is of a rear dining room. The left wall being a party wall. It looks like the concrete oversite does not extend fully to the base of the walls, with the rest being I assume clay of some sorts. The clay was dry yesterday, and now very wet to touch.

Any help would be appreciated
Kind regards

 

[tell80]

Will you please post pics showing the length of the outside of the RH wall at ground level?
You have damp thats penetrated and then become rising damp.
The penetrating water could be from ground water or high ground levels?
The blue brick courses are presumably your DPC but still check for a DPC in a mortar bed.

Is there a chimney breast near that corner?
Carefully examine the flooring and wall at skirting level on your outside walls.

 

[Satkin]

Hi there.
See attached image of external wall.


The outside area is resin up to the grass.

Looking at the attached next door neighbours ground level it appears to be the same, but they have paving slabs with a small gravel trench next to their wall.

Looking at the neighbours to the other side which isn't attached, their ground level is a bit lower.

There was a chimney in that corner, it was removed and replaced with a concrete slab which touches the internal wall. The plaster above the old chimney area is crumbling and much darker in colour, but seems to be restricted in an arc pattern to where the concrete is.

I can't seem to see a physical dpc other than the blue bricks, but what I have noticed is the internal leaf double blue brick is at least 1 brick lower than the external leaf.

Kind regards

 

[^woody^]

I wouldn't worry too much about water in the floor void. That's normal and expected.

The paving seems to be sloping towards the house, has the cavity been checked for blockage? There does not seem to be associated staining on the external wall, but you may want to check.

Also check the window for signs that water is not entering the cavity from there.

If the cavity is clear then you'll need a new injected DPC

 

[tell80]

You might be able to check the cavity from the obvious interior air brick opening - if the air brick is not sleeved you could use your camera to look inside the cavity.
There's no sign of the new air brick opening inside on the inner skin?

Does the sub-floor ventilation provide through ventilation from rear elevation to front elevation?

Perhaps you could supply pics of the old chimney plaster (party) wall - & further along the inside of the right hand wall?
I would replace the rotted joist,
and probe the other joists where they seat in wall pockets.

That the neighbour has some kind of French drain suggests that they've also had damp problems.
Are you on some kind of hill slope?

 

[Satkin]

Hi Folks, apologies it has taken quite some time to respond. been very busy with remedial works, including having walls knocked down!

I have done a lot of digging over the last 3 months. Found that the cavity walls were full of wet sand/droppings above the damp proof course, both our side and the neighbours side, which is causing damp to the front and back of the property party wall.

Still have a bit to dig out in other areas, and trying to convince the neighbour to have her cavity cleaned also, but so far ive managed to get the majority down below the DPC.

We have also found that the kitchen floor (Concrete) is simply a 1/2 inch think poured slab on top of coal and sand which is wet and bridging the DPC. I am ripping the whole thing out this weekend, and have a Joiner on standby ready to replace the dining room/living room and kitchen with suspended timer floors.

We have been advised to drop the ground levels and install some drainage, which we will do at some point as we are currently not experiencing any water in the subfloor.

I have also found that the dining room hearth from the removed chimney (image below) was bridging the DPC. Removed everything there down to the oversite and seems a lot drier.

The chimney in the living room was also backfilled under the hearth with wet sand/coal above the DPC (images below) which i have now dug out completely to the oversite, with a plan of putting in concrete lintels to act as a base for a concrete slab so we can put a log burner in keeping it from bridging the DPC.

my question though, is now I have just about removed all the bridging from the house. How do I make everything good?

I am planning to install a chemical DPC around the whole ground floor as a just in case scenario in the mortar bed above the Blue Brick. All new joists which are going in are going to be pre-treated and have DPM around the ends and on top of any sleeper walls.

But I am not sure what to do with the walls themselves in terms of plastering as the walls are obviously still a little wet.

I have been advised that I should fit a meshed membrane to the walls where the chimneys used to be/are currently, as well as any areas which have previously been bridged, then plasterboard on top of this to ensure we are protected against the next door neighbour, as it is very likely that they also have backfilled chimneys that are bridging the DPC.

any other ideas?

kind regards