Penetrating Damp - Advice Please

[Skavenger]

Hi

I have a couple of areas of penetrating damp in my House especially prevalent during heavy rain. The affected area is under a UPVC window in the front room.

Looking at the external wall there are no obvious defects above the window in the brickwork or around the window (but i need to double check).
The pointing however at the bottom of the lowest layer of bricks is quite bad.

If there is no water entry above the area could water seep through the gaps in the render through the cavity and into the wall??

My plan is to repair all the pointing outside but I have also though about painting the walls with a silane based waterproofer such as advised here:

//www.diynot.com/forums/buildi...amp-problems-once-and-for-all.336013/#2500924

Or will silane based waterproofer make the problem worse by retaining moisture, if a chemical waterproofer is a good idea can someone offers some recommended products and I guess I should wait for some dryer wether before applying it!!!

The building is aprox 1930 terraced brick cavity built on what appear to be stone footings with a slate DPC. The front of the building is concrete which appear to be above the DPC? The front room where the problem is has a hung floor.
Thanks

Damp Wall Inside Front 2

• Skavenger
• 19 Jan 2014
• 1

Damp Wall Iside Front 1

• Skavenger
• 19 Jan 2014
• 1

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[HERTS P&D]

You need to post pictures from the outside.

Andy

 

[Skavenger]

You need to post pictures from the outside.

Andy

Will do, its getting dark now so i'll do it in the morning.

 

[conny]

Are you sure its a cavity wall?

There are a lot of houses built around 1930 that were not cavity based. One way to check would be to look at the brickwork below the render. If you can see brick ends, rather than full length bricks, every so often then it won't be a cavity wall. More likely a double thickness cross bonded wall. Whilst you say it is a slate dpc these can fail over a long period of time and it may be that the internal section has done so.

 

[Skavenger]

I definitely know the kitchen wall is cavity but this is a later extension (circa 1960) however the front wall is about a foot wide so I would guess its cavity?

I'll take a look for Brick ends tomorrow to be sure.

 

[conny]

Chances are that if the wall is about a foot thick it will be solid. A cavity wall will not be as thick, 3" deep outer brick, 3" gap, 3" deep inner brick/block plus a thin plaster skim.

On an older house that is double bonded the cross bonded bricks will be 9" from the inner to the outer and the internal plaster tends to be at least about 1" thick so although similar they will have totally different characters.

 

[Flyboytim]

As a general rule, if the thickness of the wall is the same as the length of a brick, plus about 25mm for plaster etc, then the wall does not have an appreciable cavity, and will be as cold as a solid brick wall. Even a 25mm air cavity will have little thermal effect. Whatever the bond visible on the wall outside, or the age of the building is not a reliable indicator. My grandfathers house just outside Birmingham built in 1934 had no effective cavity, and stretcher bond - about 11 inches thick, somewhat due to lime plaster and horsehair to bulk it out. My current home in Portsmouth built before 1890 has stretcher bond too and about a 3 inch cavity The original plaster has long been replaced with a drywall finish.

However, unless there is regular and prolonged soaking of the outer wall (raised ground level less than 150mm relative to the damp proof course, leaking gutters immediately above and splash from either these or overflowing cisterns, cracks or heave due to tree root damage to foundations (which should be investigated and fixed if necessary), then penetrating damp is unlikely.

Cold air downdraughting from the windows above, chilling the wall below and subsequent condensation on that wall is more likely. The skirting appears to be a Torus pattern in fairly good decorative condition (not having 80-odd years of knocks and paint), but allied with the woodchip paper, points to a 1970s-80s replacement on a wall that has seen some deterioration over the years. Woodchip was rarely a decorative option for smooth walls! Possibly, original lime and sand plaster which detached when the original skirting was removed has been replaced with cement render creating a cold, impermeable bridge to the brickwork.

Point an ordinary unheated fan at low speed at an angle to the wall to provide a countercurrent of warmer air from within the room for a few evenings. This will dry out and warm the wall.

Probably drywalling with an insulated board will be the simplest method to prevent this in future. It also does not need to be continued to the top of the wall, as far as the dampness is concerned

 

[tony1851]

A cavity wall will not be as thick, 3" deep outer brick, 3" gap, 3" deep inner brick/block

 

[conny]

A cavity wall will not be as thick, 3" deep outer brick, 3" gap, 3" deep inner brick/block

Realised that myself when I re-read it before. Sorry.
I think best method is to check for header bricks in outside wall.

 

[Skavenger]

Many thanks for all the replies.
Following on from my post, I have taken some pictures of the suspect area at the front of the house.

Concentrating on the bottom layer of mortar (which is the only area with gaps) I cleaned it all up (removed any loose mortar and soil) and pointed with pre mixed mortar.

Looks a lot better now.

As you can see from the photos there is an Air Brick located at the base (there is another off to the right) this is a metal plate but I cannot see if it bridges the cavity?

Anyway here are the photos:

Outside Front Plant Ingress

• Skavenger
• 26 Jan 2014
• 1

Outside Front Low Air Brick

• Skavenger
• 26 Jan 2014
• 1

Outside Front Pointing Missing

• Skavenger
• 26 Jan 2014
• 1

Outside Front Pointed Panoramic

• Skavenger
• 26 Jan 2014
• 1

Outside Front Pointed Low Air Brick

• Skavenger
• 26 Jan 2014
• 1

Outside Front Pointing Completed Close Up

• Skavenger
• 26 Jan 2014
• 1

 

[loply]

That's not an air brick, it's a rainwater inlet.

Or at least, it is now. It once was an air brick.

Whoever laid that floor/patio wants shot. Pet hate of mine is lazy path/driveway laying which raises the ground level up to air bricks etc.

I can't really comment on a solution but at a guess I would consider blocking off the lower few inches of that air brick (maybe just fill it with mortar and sort of 'render' it) to at least mitigate the amount of water getting in...

 

[Skavenger]

Mmm;

That was my thoughts as well hence posting the picture.

This is a Terraced house (1 of 4), all built at the same time, three of them have the same raised front but one appears to have removed the raised patio and replaced with gravel but still up to the same level.

My thoughts are at some stage to dig out the concrete and lower the patio.

Its only a small area to the front of the house adjoining a main road (approx 2m deep and spans the front of the house) its not used for anything.

When I was pointing I filled in the bottom layer of holes to prevent water ingress, its raining now and there is no pooling in that area

At the back of the house 1/2 the width of the rear is a bathroom extension, the previous owner has laid a concrete patio and again has done so above the DPC!!!

 

[ban-all-sheds]

My thoughts are at some stage to dig out the concrete and lower the patio.

//www.diynot.com/forums/building/damp-proof-course-and-dry-channel-needs-concrete-bed.364196/