Garden Retaining Wall - waterproofing

[shazauk]

Hi Im after some help with a 3ft retaining garden wall and the best method to make the soil side watertight. My intention is to have it rendered on the front and then painted, the wall is made out of 7n heavy concrete blocks. Any advice would be very much appreciated. At present the wall has been constructed but can not move forward with back filling with soil till i know which is the best and kind of cheapest method of waterproofing as i dont want the render to blow off years down the line.

Many thanks

 

[freddiemercurystwin]

A sheet of dpm down the back, with a protective board and some drain holes in the bottom.

 

[shazauk]

Would this be any good to paint on the blocks......Liquid Damp Proof Membrane or do you think the sheeting is still the best method?

 

[freddiemercurystwin]

Both would be belt and braces!

 

[shazauk]

Ok you do realise you talking to a woman who has no idea whatsoever with technical builders jargon!! lol.... if you could, do you have any exact products you could point me in the right direction... sorry to be so dim!

 

[richjamesw]

your best with liquid dpm painted to the back of the wall, i.e. the earth side, you then need to drill some holes through the wall about 1 inch dia at 1200mm apart from each other. they should be angled at say 30 degrees to the floor. hope this helps.

 

[freddiemercurystwin]

Drill of core drill or have someone put some holes in the bottom of the wall like this

Paint the back of the wall with a couple of coats of this http://www.toolbank.com/p/EVB90101

Then stick a layer of DPM over the top http://www.screwfix.com/p/black-membrane-1200ga-3m-x-4m/73066

Then to protect the DPM from the earth lay a sheet of something like this against the DPM before you backfill the earth http://www.riw.co.uk/ProductPages/ProtectionBoard.aspx

Any builders merchant will carry an equivalent product for the three examples posted.

 

[shazauk]

Thanks richjamesw & freddymercurystwin - Your comments have been very helpful and many thanks freddy for the links..... to protect the dpm from the earth do you think i could get away with polystrene? i had also intended to put a inch think of peashingle against the dpm for drainage.. Your thoughts would be appreicated...

This will teach me for seeing a garden design and go to copy it in my garden, didnt think sticking up a raised retaining flowerbed wall would be so technical lol.. I guess im just paniking that the render i put on front doesnt blow off due to damp as i have heard of people having this problem and as im looking for a comtempory look i dont want it looking tatty after a couple of years.

 

[freddiemercurystwin]

Yes a bit of polystyrene will be fine and the pea gravel won't do any harm. You are right to be concerned, the forum is littered with failed renders on retaining walls with inadequate waterproofing/drainage.

 

[macadonald]

Hi,

I can talk from recent experience, where last summer I built a series of 3-4ft high walls filled with earth, which form the 3 sides of a decked area. I used this forum and had similar responses.

I used a liquid membrane bought from Wickes and painted 2 if not 3 coats of this and don't hold back at corners. Slap it on. I didn't have drain holes, but then mine isn't a retaining wall as such and the water simply drains down into the ground.

Regarding render on the outside, I used a waterproofer in the mix and once very dry painted it with a good outdoor paint.

Lastly, it's pointless doing all this if the top of the blocks are open to wet. You could simply render this, but it may get damaged and crack. I cut down slate tiles and created what I think is a good looking capping.

No problems yet and btw, I also copied an idea I saw somewhere else.

 

[shazauk]

Hi Macadonald,

Thank so much for your information, it sounds very similar or infact identical to what im trying to achieve. Maybe retaining has been a wrong word as it is more of a high wall raised flowerbed which also is 3 sides of my small garden with a decked area and only about 2-3ft in depth. This also drains directly onto soil.

Do you know the product name you used at wicks for the liquid dp as i also looked at one of these yesterday but said not for retaining walls.. not sure if this was just covering their butts. I was thinking if i use the liquid directly onto the concrete 7n blocks and then an actual dpm as well im making double sure water will not penetrate, im guessing these products wont conflict with each other?

I will also be making sure i cap the top of the wall and also had been suggested to use cut tiles (as i didnt really like the coppings i've seen)

Once rendered i was going to use Sandtex masonary paint..... would you suggest this is a good external paint?

 

[freddiemercurystwin]

If you really want the business get either RIW LAC http://www.riw.co.uk/lac.htm

or SYNTHAPRUFE http://www.ruberoid.co.uk/pages/rub...product_page/default.aspx?CatID=57&ProdID=161

Most merchants should carry one or the other, prob about £30ish though. As ever you generally get what you pay for though.

Given the small expense of a sheet of dpm its pointless to avoid it, there won't be any incompatibility issues.

Personally I'd avoid Wickes.

 

[shazauk]

Cheers Freddy, you have been most helpful, thank u so much. I can now start this process. At last i might get to see my plants planted before the end of summer

 

[marky9074]

Damn, I wished I had asked a similar question when I did this last year! I assumed that the builder would take this rather serious issue into consideration..

See my thread (sorry, I should have just added to this one rather than create new one but I didnt see it until this morning)..

//www.diynot.com/forums/viewtopic.php?t=279031

So what are you going to go for? I am bordering on digging all my plants out and fitting DPC sheet...

 

[shazauk]

Hi Marky9074,

Sorry to hear your having problems with your render, this was my concern once i had decided to start this project in my garden. I must say the people on here have been invaluable with the help and advice given, especially "freddymercurystwin".

I've decided to paint the dmp liquid onto the concrete blocks, then cover with dpm sheeting, then some polystrene and some gravel for drainage. I know this may seem a bit extreme but to be honest, i'd rather go overboard than have the problems you have experienced and many others. I'll also be making sure that the render will have waterproofer in the mix also.... then it will be fingers crossed.

To be honest and im no builder, just a mere woman with a vision for her garden.... i'd do it properly now and save yourself more heartache and expensive a year or two down the line again maybe? Btw..pics of your garden look fab