damp exterior wall

Members online

Status
Not open for further replies.

windy

Private Member
Had a call from a tenant of mine. We have a extention which has an exterior wall (single skin) which has suffered from damp for yrs. In the winter the outside wall gets soaked and penetrates inside to the interior walls causing water stains and the finish plaster to blow. The gutters are ok and there are no leaks around the window unit. THe pointing is solid but appears to be retaining a lot of moisture.

Externally i was thinking of hacking out old mortar and repointing. Then will a water ressitant render (krend etc) be any use once the repaointing has been done?
 
sorry just re read my post. Red engineering brick. two skin but not much of a cavity between
 
That I couldn't tell you in all honesty. I've only used pre bagged a number of times unlike a lot on here. However s+c has been used for years so it must be doing something right. Its cheap and relatively straight forward for a competent spread. Or use hp12, its a base coat but I've used it for both coats and when rubbed up with a sponge float it leaves a nice effect imo.
 
You might find that it's the relatively solid wall being cold doesn't help and would add to it taking an age to dry out. Also creating dew point problems of mould/condensation of its own as well as the penetrating damp. Really it needs externally insulating with a modern render on top but how far do you go with these things?
 
wud try and get some pics but there is a tenant in the house and its 5miles away :RpS_crying:

The reason i felt it would be penetrating damp caused by poor pointing as the section of wall on the onside which is damp and causing the internal problem joins on to a newer brick section of wall (built at a later date.) That wall is bone dry inside and out ?
 
rake out deep and re point with lime nhl 3.5 lime that will be cheap enough to begin with and allow any trapped moisture to escape, however if it was built using cement mortar then this will not help, you can check if it was built with lime as there will be little white bits in the mortar
 
wud try and get some pics but there is a tenant in the house and its 5miles away :RpS_crying:

The reason i felt it would be penetrating damp caused by poor pointing as the section of wall on the onside which is damp and causing the internal problem joins on to a newer brick section of wall (built at a later date.) That wall is bone dry inside and out ?

ah ok, recently I came across a ruptured water pipe that was under an extension. That was on me mind, that's all :RpS_wink:
 
You might find that it's the relatively solid wall being cold doesn't help and would add to it taking an age to dry out. Also creating dew point problems of mould/condensation of its own as well as the penetrating damp. Really it needs externally insulating with a modern render on top but how far do you go with these things?

Goody has got this one right. No matter how much you waterproof a solid wall it is still going to be cold. Unless there is adequate heat and ventilation on the inside you will always have problems.

Insulation on the outside is the better because of the dew point and dry bricks.
 
the word we are looking for is permeable which lime is but if the face of the brick is fecked then repointing maybe not be the solution/
 
As soon as a wall becomes wet it loses almost all of it's insulation properties, so you got to:
1. Make it watertight.
2. Allow it to dry.
3. Apply a waterproof/resistant system to the exterior.
4. Insulate further inside if practicable.

And tell the tenant to get the windows open - you've got no chance:-0
 
wud try and get some pics but there is a tenant in the house and its 5miles away :RpS_crying:

The reason i felt it would be penetrating damp caused by poor pointing as the section of wall on the onside which is damp and causing the internal problem joins on to a newer brick section of wall (built at a later date.) That wall is bone dry inside and out ?

You have just answered your own question...
 
tell me about tenants. Drying clothes in the kitchen always causing problems and they will never open the windows!

Thanks for replies so far

1 Where do i buy nhl 3.5 lime
2 Would air vents help?
 
My friend next door neighbour.So has to be right.
Front room im going to take off meter high and use limelight/drywall stuff.

Do I need to two coat like s+c scratch coat and top coat??

Upstairs,black spot mold old looking background,easyly fingered/rubbed off bit damp and black mouldy,not to much ,just here and there.Having trouble with condensation,black spot keeps coming throught the walls here n their.Thats the main problem,the black mold,its not coming through guttering as that has been repaired.

RECKON I HACK THE LOT OFF? S+C....AND THEN SUGGEST DEHUMIDIFIER.


Thanks any help about the black mold will be very apprraciated
 
tell me about tenants. Drying clothes in the kitchen always causing problems and they will never open the windows!

Thanks for replies so far

1 Where do i buy nhl 3.5 lime
2 Would air vents help?

If you are going down the lime route then first sort out the pointing. I suggest then you use Limelite or Drywall. Both have a lime content but are lightweight due to having vermiculite as aggregate so is not as dense as S&C. You will have breathability, waterproofing and as it's insulated (vermiculite) it will not attract condensation.

You could fit trickle vents to the windows or if the chimney breast is out of use fit a plastic hit and miss air vent and put a mushroom on the chimney pot. You should do this anyway with bricked up chimney breasts.

If you have a mould problem then you could get sued for causing asma. Consider fitting an Envirovent unit. Usually fitted on the landing ceiling. About £450 but with one of these units you can have all the windows shut, no ventilation in place and the company guarantees no black mould. It conditions the air and takes out all the excess moisture. Uses 4w of power a day and cost pence to run. It takes out all the worry of being sued for causing medical problems caused by inhaling the spores from black mould.
 
ok lads great help. Pointed re done, hit and miss vent fitted and tenant told to open windows occasionally. There where cobwebs on them :RpS_scared:

Right to the inside! there are salts in the wall approx 3mx2m so gonna hack affected area back to brick.

So whats the best approach to the internal render. S&C with waterproofer then reskim???
 
Sand and cement with waterproofer is cold and dense so could attract condensation. I would use limelite Renovating or Drywall. Waterproof, breathable and lightweight.
 
right tenant moaning now so have to crack on with job. Wall was repointed weeks ago and we fitted hit and miss vent from kitchen to outside wall.

Now i need to hack off old render internally. I am going to float it with drywall then reskim. Questions r

Once i hack off damaged plaster back o brick do i need to let bricks dry out a bit or can i crack on with float coat same or next day?

Can i apply both scratch and top coat of drywall in same day ? Or leave scratch overnight?

thanks
 
1. It's always better to let the wall dry out as much as you can and then plaster it

2. As its a lightweight plaster you can build it out to quite a thickness that you cant with sand and cement it should only take a day to do and skim next day.
 
great bod thanks:RpS_thumbsup:

What timescale would you suggest to let wall dry once render hacked off? Give me an excuse to delay the job even more!!
 
Depends how damp it is? if its really bad I would leave it at least a week getting plenty of ventilation but i would check it every couple of days, is the damp cured now from the outside?
 
sorry just re read my post. Red engineering brick. two skin but not much of a cavity between


If its a cavity wall built in engineering bricks it sounds like you have a bridged cavity. Depending how much money you want to throw at it I would
1. Render outside in s+c using normal sika w/proofer
2. Render inside using sovereign renermix
3. Dot n dab with thermal board
4. Put in some air bricks at high level
 
Status
Not open for further replies.
Top