Outdoor Garden wall re-rendering

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Looked at a job to re-render an outside garden wall which lies beside some steps going up a garden. Behind the wall the garden is raised high so pretty sure soil/earth etc is behind it. The render was soaking wet, which i figure could be two reasons, a. being the soil behind and b. the render went right to ground level..

Going to take all the render off and let the bricks breath a bit, but what would be the best way to prevent moisture coming from the wall?

• Tank it out (if yes, what should i be looking for, never really used tanking before - only rendered over when someone else did the DPC..)
• Bring the render off the floor so its not on ground level.

Is above the best way to do it? I can explain to the customer the fact that its pretty hard to guarantee due to the soil sitting behind the wall, but obviously take preventative measures.
 

malc

TPF Special Forces
the wall needs tanking the side that the earth is against.
i would not quote for that job.
 

SpankySouthport

Private Member
Looked at a job to re-render an outside garden wall which lies beside some steps going up a garden. Behind the wall the garden is raised high so pretty sure soil/earth etc is behind it. The render was soaking wet, which i figure could be two reasons, a. being the soil behind and b. the render went right to ground level..

Going to take all the render off and let the bricks breath a bit, but what would be the best way to prevent moisture coming from the wall?

• Tank it out (if yes, what should i be looking for, never really used tanking before - only rendered over when someone else did the DPC..)
• Bring the render off the floor so its not on ground level.

Is above the best way to do it? I can explain to the customer the fact that its pretty hard to guarantee due to the soil sitting behind the wall, but obviously take preventative measures.
Just ordered some tanking from R and J £23 each coveres 8m2 at 2 coats
 

chickenlegs

New Member
Garden retaining wall

I have a similar issue with an external brick (and part block) faced retaining wall that has been rendered in the past but failed due the dampness of the wall. We removed the render about four years ago and got someone to batten out the wall and fix cement particle board over it. This has lasted surprisingly well given the rain we've had. The wall is about 1.5m high and 7.5m long and acts as a retaining wall for the garden behind. I would imagine that there is no waterproofing membrane behind the wall as it stays damp for most of the year. The board is now showing signs of failure and needs to be replaced with something more permanent. Does anyone have any suggestions? I like the sound of the KA Tanking slurry. Do you think I should also use expanded metal lathe on the wall to keep the render firm? Are the any other products that I should consider?
Thanks
Chris.
 

Arti

Well-Known Member
I thought someone on here said the KA slurry was garbage.............:RpS_unsure:
 

raggles

Private Member
I am being serious here i can remember seeing 2 spreads do this many many years ago on seperate occasions when i was an apprentice. the first was a retaining wall on the promonade at roker and i was sent to the local shop to get 2 bags of sugar and these were added to the dubbing/scratch coat. Nothing else ie chemicals were added to the mix and the render as far as i know is stll in place today. the other was a garden retaining wall on an old country house just outside durham and again as far as i know it is still in place today. Has anyone else ever seen or heard of this ?
 

chickenlegs

New Member
Carlos many thanks for your suggestion. I have been looking at the Newton 508 mesh and it looks like it could be the answer. My only concern is that water could be retained behind the mesh and freeze in the winter which could push the render off the mesh. The product appears to be best suited to internal applications where the temperature is unlikely to get to freezing point. Any thoughts?
 

Arti

Well-Known Member
I am being serious here i can remember seeing 2 spreads do this many many years ago on seperate occasions when i was an apprentice. the first was a retaining wall on the promonade at roker and i was sent to the local shop to get 2 bags of sugar and these were added to the dubbing/scratch coat. Nothing else ie chemicals were added to the mix and the render as far as i know is stll in place today. the other was a garden retaining wall on an old country house just outside durham and again as far as i know it is still in place today. Has anyone else ever seen or heard of this ?
were you working for hansel and gretal back then raggle.......................:RpS_wink:
 

bubbles65

Private Member
Dig the soil out behind the wall - down to the footings - then either:
1. Drill some weep-holes through the wall, placing some mesh over them on the soil side and fill with pea gravel about 12" deep. Then back-fill it.
Unless there is a drain you can tap into, in which case do that and you won't need the weep-holes.
2. Thoroughly clean the back of the wall and apply a tanking system, then back-fill.
Or a combination of the above......................... The idea is to take the pressure off the wall and therefore relieve the water penetration.:RpS_thumbup:
 

chickenlegs

New Member
Bubbles65
Although I appreciate that this is the right approach, due to the amount of mature planting in this part of the garden, it is going to be impossible to dig out the soil behind the wall. Thank you for your suggestion, tho.
Chris
 

chickenlegs

New Member
Nisus
Not sure about Wallcrete, but the Aqua Panel is certainly an option. I wonder if there is a minimum order for this type of board? I assume this is a Knauf product and can be obtained through a builder's merchants?
Chris
 

Runswithscissors

Private Member
Hi Chickenlegs (great name... could be me! LOL)

Knauf Aquapanel Exterior is sold in 54m2 pallet loads to merchants and distribution..... most will split the pallet for a cash buyer....

Make sure you ask for the 12.5mm exterior boards - most will have interior in stock, but this is not tested for external use....

if you need any further help - my contact details are on my profile (click on my profile name, top left of this post and then view profile - search from there).

Where are you based - maybe someone can offer to quote and do the work for you.....?

Good luck
 

Runswithscissors

Private Member
Oh - just spotted you are in Bristol - sorry

Encon and CCF have Aquapanel Exetrior on the shelf.... but feel free to shop around the merchants like TP, Jewson etc....

good luck
 

chickenlegs

New Member
Runswithscissors - equally amazing forum name! Many thanks for your help. I will give CCF a ring tomorrow as they have a Bristol branch and see how much the job would be as a dry lining project as a posed to a rendered job. My concern is that it will work out very expensive as the Knauf system needs a number of other products (mesh, joint filler, joint tape, stainless screws, breather membrane) as well as a render top coat to complete the job. The wall already has been battened out with treated softwood battens so at least that part of the job is done.
Thanks again.
Chris
 

Runswithscissors

Private Member
Hi Pal

it is not a dry lining job...more a rendering project...

check the battens are OK, apply aquapanel to the battens (use external grade screws, approx 40mm long) and then apply a basecoat and mesh to hold all together - then finish coat when the base is dry.

The various other products are for new build projects and needed to comply with various insurance and building regs.....
 

carlos

Private Member
Carlos many thanks for your suggestion. I have been looking at the Newton 508 mesh and it looks like it could be the answer. My only concern is that water could be retained behind the mesh and freeze in the winter which could push the render off the mesh. The product appears to be best suited to internal applications where the temperature is unlikely to get to freezing point. Any thoughts?

Your concern is unjust mate as your render is on the dry side of the membrain. An moisture is behind it. The 8mm studs are designed to hold the membrain off the wall to allow air and water movement behind. Any freezing will be there not between the membrain and render.
 
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