damp and fireplace questions

[slc304]

Hi all,

New to the forum and new to house ownership. Just brought a 1912 3 bed semi-detached house. Structurally very sound with cavity walls. However, the building survey noted a damp wall on the gable end. The damp patches rise up to approximately 60 cm from the ground and coat the bottom of the chimney breast (bricked up) and the alcoves either side. I hired an independent damp surveyor (after two 'free' surveys that amounted to 20 minutes and 6 minutes repestively - and no suprise resulted in 'you have rising damp and need a chemical DPC'). The independent surveyor confirmed my suspicions that the source of the damp was water pooling against the side of the house when it rains (the driveway slopes towards the house!) and also not helped by a neighbours overflowing drain. The gable end is also cement rendered down to ground level and over the dpc - the render is sodden towards ground level. The damp surveyor and myself noted that 3 of the 4 airbricks on the gable end are partially filled with render. I went to clear these out today, drilled out the render but discovered that each vent is full to the brim with dirt and debris, more so than I could scrape and hoover out through the holes. I used a borescope to confirm. The airbircks are a good 20cm above ground level. This is undoubedtly contributing to the damp issus. Anyway, that's the background...

My first question: Any ideas what's happened to the air bricks/vents?

My second question: I am starting to tackle the damp issue and will get the render removed and a trench drain installed so the driveway drains properly. I'll then get the vents cleared, inspect the cavities/clear if required and then see to the plastering. I've been stripping the wallpaper on the gable end to reveal the (damp) fireplace that we would like to open up. After removing the paper I am left with this (see images). The white is original lime plaster full of horse hair. The grey appears to be concrete filling some holes but any idea whats been going on? More so, what are the green areas? They were covered in a thin layer of grey concrete(?). They look like block work but from the second image you can see from the cross section that this is only a cm deep or so. Any insight would be appreciated!

Many thanks,

Sam

 

[Abi Cott]

Welcome to the forum

It sounds like you're on the right tack. Opening up the fireplace will help a fair bit too I should think.

Is it staining from a previous mantle?

 

[88v8]

Hello and welcome.

You're off to a good start, not falling for the snake-oil damp treatment schtick.

As Abi says, opening up the fireplace may help with the damp, especially if the chimney is open to the elements at the top.

Yes indeed, there would have been a mantelpiece there, perhaps set into the plaster, and the cement could have been used to fill the holes when it was pulled out.
Are there any other mantels in the house?
The green blocks are not apparent in your pics... ummmm, tiles?

Bear in mind that if the chimney has been sealed at the bottom but not the top, and if the fireplace had been used in the past - I say if because bedroom fireplaces sometimes were never used - you could have soot staining leaching through due to damp in the flue. It would show up first in the mortar between the bricks, so you could get a sort of block pattern. Hopefully not.

The air bricks are presumably ventilating a suspended (ie wood) downstairs floor. There should be counterparts on the front of the house.
Is the downstairs fireplace still there?
I ask because it's not unknown for builders to use the underfloor space as a dump for debris if a fireplace or chimney is removed. I'd be taking up some of the boards adjacent to the gable wall, to have a look and see if that's the source of the debris you mention. Underfloor ventilation is important; rot beneath the floor you do not want.

Ivor

 

[MatthewC]

Hi Sam
You've got the right ideas and come to the right place but

... not helped by a neighbours overflowing drain.

would also be a good place to start!

 

[Lime]

My first question: Any ideas what's happened to the air bricks/vents?

Most vents get blocked with spider web and other insect debris, detritus, soil and. depending on how wet the wall gets, calcium deposits.
The design of many brick vents is not good either as the apertures often funnel down to next to nothing.
On windy days many people would probably be surprised at how much air travels through the vents and as a consequence they act as course filters and eventually block up.
Even if the holes are apparently clear the void in the wall behind may be clogged with dirt and web.
I regularly clear my house vents using a combination of compressed air and a long thin piece of wire or rod.

On windy days I expect to see the plants near the vents to be waving about in the air stream, then I know my subfloor is being ventilated.

 

[MatthewC]

Even if the holes are apparently clear the void in the wall behind may be clogged with dirt and web.

Or, as I found, blocked by a huge wadge of concrete on the inside, which I only found when I sorted the suspended floor a few months after clearing the outside of the vent!

 

[CliffordPope]

I ask because it's not unknown for builders to use the underfloor space as a dump for debris if a fireplace or chimney is removed.

Indeed yes. In a previous house I found the original complete marble fireplace in sections lying under the floor.
(In company with a bizarre collection of beheaded garden gnomes, and old furniture slowly rotting into the soil)

 

[slc304]

Thanks all, glad it sounds like I am going about it the right way. Just waiting for a few builders to get back to me now. In the meantime I have had a go at the air bricks on the other end of the dining room (rear elevation) and they too are completely full to the top of dust and debris, so much so that it just keeps on coming no matter how much I remove. This lends me to think that the under floor void is packed with rubble/debris of some sort (I can see a small outhouse used to be adjacent to the dining room so perhaps it's now under the floor!). I would lift a section of the floor but the misses is putting her foot down for now! I have also noticed that three of the four air vents on the gable end wall are the more modern air brick type whilst one is the original iron style. The iron style one is one course of bricks lower than the brick ones... Strange...

 

[88v8]

I would lift a section of the floor but the misses is putting her foot down for now!

For now may be OK, but if the underfloor vents are blocked then the floor will suffer. It is ventilated for a reason. Dry rot is not very nice.

I have also noticed that three of the four air vents on the gable end wall are the more modern air brick type whilst one is the original iron style. The iron style one is one course of bricks lower than the brick ones... Strange...

The cast iron type are better as they are less restrictive than modern terracotta.
Replacements easily had from your local salvage yard, or new ones here
https://www.castironairbricks.co.uk/

Typically they sit just above the damp course.
You mean the bottom of the air brick is higher, or the top? Are they the same size - usually 9 x 3" or 9x6" or sometimes 9x9".

If larger air bricks have been inserted that suggests there was a problem with the ventilation, but then why exacerbate it by clogging up the air bricks. Perhaps the new air bricks was one lot of builders, then the clogging up was another.
It can be hard to unravel the history of a house.

Ivor

 

[slc304]

Thanks for the helpful replies. In answer to the last query the cast iron air brick sits in the row of bricks below the more modern terracotta ones. Having had a closer look at floor levels I'm not entirely sure the terracotta ones are truly beneath the floor. They are almost in line with the floor boards. I am beginning to wonder if the modern looking air bricks are in fact venting the wall cavity and the cast iron one is venting the under floor (I can see through the cast iron one beneath floor boards). This would mean that the cavities are full of debris. However, where are the other under floor air vents? Beneath the concrete render perhaps or beneath the level of the concrete drive?. I would have expected them to be in the same course of bricks as the one remaining cast iron vent... It's an annoying mystery.

 

[slc304]

Hi all,

thought I would post an update on these issues. Had the cavities opened up today and no surprise they were absolutely chocker with debris up to approximately 70 cm from ground level - all sorts including bitumen-like products, flint stones and a whole load of degraded mortar.



Unfortunately the fireplace is not in great condition, looks like a lot of fire damage, especially to the right hand side where most of the bricks have fallen apart. Any suggestions on how to make this good - render the whole lot? Need a new hearth as well. Ignore the missing bricks, easiest wat to remove all the debris in the fireplace - it was head height!



Cheers,

Sam