Can anyone help me. I have just moved in to a 1930s detached house. I have found what looks like corrugated bitmuen sheets that have been plastered on downstairs walls. does anyone know what these are? I think they may be to solve a damp problem theough i wonder if they are just hiding the bigger problem as some of my floor joists have rotted away. should i leave them and decorate over them or take them off and get someone to plaster the wall? any help please?
what are the black bitumen sheets under my plaster?
- Thread starter woodymartha
- Start date
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They sound to me like rolls/sheets of plastic corrugated lath. I have used similar many years ago, (in the 60's) to render onto, (externally). The corrugations were a dovetailed shape to hold/key the plaster/render. It came as a roll, about 2 or 3 ft wide. Each roll was then cut into the required lengths, and each length was fixed onto the wall surface, vertically, with the dovetailed lath effect, running horizontally. The plastic lath was then scratch coated, and rendered in the usual way.
I don't think i would take them off, without checking a small area first.
Any chance of a picture?
That sounds like them. I'm glad someone knows what i am on about. Checked the internet and found nothing. All i can see is faint lines (horizontal) on my wall with the black comming through in places once i had taken the wall paper off. Is it part of a damp proofing method? do you know if it is a good one or should i start again with damp proofing?
forgot to say that they are on the internal walls. Is this bad??? 
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We, at that time,, only used them on "external walls", but there would have been nothing wrong at all using them internally too. It "might" have been used as an early form of damp proofing, who knows,, but we used it primarily, to provide a key on old smooth brickwork/walls that didn't have much of a key/grip. It was a mechanical key, (on a roll) for rendering onto. I would check it out as regards to it being an adequate damp proofing method nowadays, and don't forget, this material was fixed to the wall in strips, and they didnt overlap each other, just butted up. I would get advice from a damp specialist, and also investigate the problem with the rotten floor joists.
Thats great Roughcaster. Thanks so much for your advice. It's good to know what i am now dealing with. Had the damp checked out and they said it was all over the house and needed a full damp course. The house had been unoccupied for over a year and all ventillation had been sealed up. After only 4 weeks of living here the house feels much drier so I am going to wait abit and get it checked out later in the year to see if i really have a serious problem. Thanks again for your great advice.
Be careful here, have you had more than one survey for damp?
It could very well need a new DPC, but if there has been no ventilation that may be as much of a problem to solve first. Perhaps teh DPC or damp proof render just needs to be more localised (and cheaper!)
Read this
//www.diynot.com/forums/viewtopic.php?p=763954#763954
You will need ventilation anyway, so that won't be an extra cost- and merely by opening doors and windows you seem to have alleviated the problem.
Check air bricks around house are not covered -this may be the floor problem perhaps -check on the other forums here for advice.
It could very well need a new DPC, but if there has been no ventilation that may be as much of a problem to solve first. Perhaps teh DPC or damp proof render just needs to be more localised (and cheaper!)
Read this
//www.diynot.com/forums/viewtopic.php?p=763954#763954
You will need ventilation anyway, so that won't be an extra cost- and merely by opening doors and windows you seem to have alleviated the problem.
Check air bricks around house are not covered -this may be the floor problem perhaps -check on the other forums here for advice.
Very wise advice Micilin has given as usual. Always get more than one survey for this kind of thing. If you rely on just the one survey,, you'll get all the waffle under the sun, and may be ripped off. Get 2 or 3 to be on the safe side.
Leaving the windows and doors open, especially at this time of year as Micilin said, will definitely have helped improve the situation greatly.
Can any one tell me if this product is still made ? ,I have a wall in the garden that is a retaining wall ,the wall is rendered but is constantly wet and when we have a frost it blows the rendering off . I used this product in the 70,s on a damp internal wall and it worked and my thinking was if I used this lath with a gap between the lathe and ground the water would still escape but not blow the render off (when re rendered on the lath), I cannot remember the products name,but think it was Bitumastic or something similar
Edit for spelling mistake
Edit for spelling mistake
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