Various water ingress problems extension bathroom. Short term / long term fixes?

[Clive]

Hi,

This follows on from a previous thread on my extension bathroom.

Summary. Victorian end terrace, brick-built, solid (2 brick) walled.

1930's extension at rear =96 exterior bricks well matched to rest of house, probably solid wall 2 brick construction also. Bathroom at downstairs back, flat felt roof, roof looks OK. NO INSULATION in walls or ceiling =96 freezing during this past winter. Interior walls plastered and covered in 1980's ceramic 4inch square tiles. No special water barriers between tiles and walls.

Interior. Tile grout was missing in a few places. Tiles around shower end of bath were lifting away (blowing) from walls and held in place only by grout. When I removed a few tiles by hand (before they fell off) more fell off like dominoes. Under the tiles the plaster was soaking wet and had a =93slimy=94 feel to it. I have been drying the walls out for a few days by leaving the window open on dry days and running a dehumidifier full pelt over night. Three people are using the single bathroom and putting up with hand basin washing but I need to get shower back in use ASAP. Functional remedy takes precedence over appearance and time consuming but =93correct=94 fixes. A fix that would last a couple of years might do. I can't afford time or money at the moment to rip down walls whole-sale. Would tiling on top of plaster, grouting carefully and thoroughly and =93masticking=94 all the corners reduce the risk of water getting behind the tiles?

Externally the walls are cement rendered. I know the construction is brick because the other two houses in the terrace have identical extensions =96 Brick built originally with sloping tiled roofs and internal steps in room. The cement render is covered in a kind of =93plastic paint=94. This =93paint=94 has bubbled in places I scraped it of= f easily exposing about 10% of the render. the render under the bubbling was a bit damp. The rest of the "paint" surface was sound and couldn't be scraped off. I bought some Homebase =93Weathercoat=94 that was going cheap. My absolute priority is to cover the render before it rains again and gets wet. Now, and this may be a coincidence but I need to mention it, the area of worst bubbling on the outside corresponded to the wet area inside. I have looked at the guttering carefully and =93tested=94 using a water hose running water over the flat roof. The water seems to run off the edge of the flat roof right into the centre of the gutter and runs away easily into the vertical drain pipe. There is no evidence (from my test) that water is somehow penetrating from roof running down walls. So I don't think this dampness / wetness in the render is due to external rainwater. This is a bit worrying. How can I find the source of the water? In the short term I'm painting the exposed render with the Weathercoat masonry paint then covering the rest of the =93plastic coat=94 with same. I'm not confident the Weather coat will adhere but I need to try otherwise the back of the house will look like it has desert camoflage on it

Long term what can I do?

Tiling and water ingress from shower and steam. Is the =93best=94 to rip the walls back to the brick , install Wediboard or similar, then tile on top? How about these =93sheets=94 used in wet rooms to act as a water barrier behind tiles? Are the fixing instructions clear? Names? Suppliers?

Insulation. I'm prepared to take off all the cement render and put on external insulation. What are my options? I would MUCH prefer to have the brick exposed and insulate internally but I guess the rendering has ruined the external appearance of the bricks. The external appearance of insulation can't be any worse than the current =93painted=94 render.

Thanks in advance for any suggestions or information.

Clive

[dom]

Is there any air extraction from the bathroom?

What heating do you have in the bathroom?

I'd suggest priorities are dry the place out (which you're doing), then install extraction (if you don't have any), then insulate - internally or externally.

I remember an old student house I lived in in the 1980's, no central heating, and a kitchen that was just the back room of a terrace - when the paper was stripped off to decorate, all the plaster on all the walls was saturated with moisture.

In fact, if all your external bathroom walls are showing similar levels of damp, it points much more to condensation than an external leak.

[Clive]

There's a big ventaxia which can keep the steam down even when the shower is going full throttle And there is a top hinged window which is opened when it isn't zero or below outside

A double panelled with fins hot water radiator ooh, 60cm by 60cm. When the heating is on it can chuck out a fearsome amount of heat - but it gets used as a towel rail often.

[dom]

Does it run continuously in the background at a low rate/switch to high rate with occupancy?

Can it be arranged to do so?

[Mike Tomlinson]

In article , Clive writes

I'm in a very similar situation. Brick bathroom on the back of a Victorian semi, open to the air on 3 sides. Damp and very cold in winter.

I had the room stripped out, a damp membrane fitted all round finished with a special plasterboard for bathrooms (can look up the brand if you want) finished by tiling.

The floor, quarry tiles laid on earth, was dug up to about 9 inches deep, sheets of polystyrene insulation laid, filled with concrete and screeded, then electric underfloor heating installed before tiling.

Pleased with the result. It's not wonderfully warm on the coldest days but the underfloor heating makes a big difference. It's on a timer to warm things up before I use the room in the mornings.

Oh, and make sure you fit a good air extractor on a timer so it runs on for some time after you have used the room.

[The Natural Philosopher]

slightly off topic, but a friend is running a workshop that is entirely unheated and uninsulated in an old barn..

200W of heating is enough to keep the moisture level low enough so that paper plans don't get soggy, and stored wood doesn't warp

The cracks in the eaves and ill fitting doors provide the ventilation.

The point being that its only necessary to raise winter air a few degrees to eliminate condenstation and damp.

[Clive]

Latest situtation

Most of the walls have dried very well.

However, there is a persistent "wetness" at the edge where the wall meets the ceiling on one wall. Outside this is the rainwater gutter. So the classic interpretation (I assume) is water is getting behind or over the gutter and then somehow creeping in.

I have checked the gutter. It is completely clear of all debris and no gaps at joins.

The roof felt looked a bit "cracked" in places where the felt curled over into the gutter.

I have put self-adhesive bitumen flashing over the edge of the roof felt and painted the edges with Black Jack primer. I have heavily masticed around the window frame where I thought there was a risk of water getting in. I have a big container of Aqua Mac coating that I'm going to paint over the whole surface of the roof tomorrow if it is dry.

Now I have put some marks on the wall showing the latest "progress" of the water coming in. The idea is to see over the next few wet days whether the water line recedes. Worryingly, some wet "spots" have appeared in plaster in the centre of the wall surface. I have looked and looked outside and can see no "point of entry" for the water from the outside. How can there be wet spots in the center of the wall surface? I can only guess that water "travels" and that water is getting in somewhere else, not the carefully "flashed" edge. But I have looked reallly carefully over the surface of the flat roof and I can't see where water could be getting in. Ultimately, if the wall doesn't dry out it will be roof felt off and replace.

This was to be a replacement of a few loose tiles. God I hate DIY 8-)