Chase for shower into thin breeze block wall

[SteUK]

Hi all,

Wonder if I might beg some expert advice.

I am re-doing our bathroom, which involves moving the in-bath shower from one end to the other. To achieve this I started to chase into the exterior wall at the end of the bath. After removing a load of blown bonding plater I revealed that the breeze block behind was not in great shape (previously had a window there that was made into one window when the bathroom was made one room from a separate toilet and bath rooms).

So, decided to ditch that plan and put the mixer on the adjacent (internal none load bearing) wall. After chasing out the channels I discovered that the breeze block wall was not the 100mm thickness I had naively assumed it was. I think it is actually 50mm, with a single internal hollow area of approx a third the thickness of the block. My chase naturally broke into this. In the none hollow areas the chase depth ranges from 25mm to 30mm. The chase is approx 50mm wide.

If I wrap and cement the pipes in, and bond and finish plaster...will this be safe enough? Or should I abandon this and cement the chases closed and think of another plan...?

Thanks!
Ste

Edit: here is a pic for reference...(looks like the host has entered it, the chases are vertical, up into the loft)

 

[muggles]

You're asking for the recipe after you've cooked your goose here...you should have abandoned as soon as you discovered that the walls were only 50mm thick. Now that you've gone the whole hog and weakened them all the way down you may as well put the pipes in the chases and hope for the best when you cement them in. Don't forget to wrap them in tape to protect against corrosion

A 30mm deep chase seems rather excessive for a 15mm diameter pipe as well, why so deep?

 

[SteUK]

Because the first layer into the hollow was so thin, it pretty much vanished.

Will cementing the chase back in not re-strengthen the wall back again?

I also noticed this morning that the current shower feeds (from a pump) vibrate a little. Not sure I want to be putting them in a weakened wall and chance it. At this stage I think I would rather make the wall as solid as can be again and rethink the solution.

 

[muggles]

How about a ceiling fed shower?
http://www.tradingdepot.co.uk/DEF/product/!!VSD.A1.EV.14!!/

 

[SteUK]

Would be a great solution, but simply do not have that kind of money to spare

Thinking the best way to solve the issue is to stud out a small box on the exterior wall in cement board - which I think we are going to have to use on the walls as the plaster is shocking, blown all over the place, and I am not convinced it will take the weight of the tile (16kg/sqm), adhesive and grout. That way I can run the pipes up in the void. Not the prettiest solution, but a safe and relatively cheap one.

Only concern is putting some strength back in the chases. I read that mortaring out can actually return the structural integrity to the wall. Should I add some sharp sand to the mortar mix as the chase is quite deep?

 

[muggles]

You'll need to ask the building forum for advice on mortar mixes

 

[SteUK]

Roger that. Thanks for your advice.