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Replacing a wall
I have a retaining wall in my garden about 6ft this is down steps from my house
I have been advised I either need it replacing or as it is stone re -rendering
3 Answers from MyBuilder Bricklayers
As you have been advised to replace it, obviously its in poor/unsafe condition.
Rendering will not make it any stronger or safer.
Best and safest option, take down and rebuild, maybe upgrade the spec, ie 225mm hollows, filled with concrete, faced with 100mm on bed stone, tied into blockwork.
Paul, you have given a good account on rendering, but dont use pva on exterior works, its not needed, if the wall is porous or not in good nick, SBR slurry, apply scratch coat while still tacky, the water proofer goes in the scratch coat plus febmix.
The scratch coat should be 4 sand 1 cement, the float coat always weaker, ie 5 sand 1 cement, no water proofer, just febmix.
If the scratch coat has dried to much, or doing it on a hot day, hose down.
You dont pva the scratch coat prior to applying the float coat with water proofer in, it will slide of the wall.
Option of adding a shovel of lime in the mix.
Answered 1st Nov 2011
Retaining walls are always tricky . Depending on whats on the other side of said wall ,or what the wall is retaining. If the wall has a [belly] Its bulging ,for instance not running straight ,i would always ,depending ,on the size ,and ,for instance how much earth is behind the wall , most probably take the wall down ,re use as much original stone as u can and ,check the found ,and redoo the found and rebuild the wall .You could also build a course of brick or block ,then build your stonework in front of that ,to give an extra barrier of strength to the wall .but i would ,if using block [preferably],build them on itheir sides ,for extra strength and durabillity. And most certainly put in weep holes to allow for drainage ,for a release of any build up of moisture .Also in my personal opinion ,using any kind of sand cement,or any other type render ,just,[retains] , holds water ,as it is obviously porous.And this wil do nothing more than add weight ,and possibly crack in cold icy conditions.I WOULD ALSO ,USE A STRONG SAND AND CEMENT MIX FOR THIS TYPE OF JOB.
Answered 1st Nov 2011
Colchester • Member since 27 Jan 2009 • 2 jobs, 100% positive feedback
Your question about the retaining wall is very vague there must be a reaon that some one had indicated that the wall needs rendering or taking down this could possible be the following.
1. The foundations are failing.
2. Tree root movement.
3. The age of the wall
4. pointing fall out i.e loose mortars.
5. Type of brick usesd and strength of original mortars could possibly be lime mixed.
6. No expansion joints in wall
7. Poorly detailed piers or lack of them.
Most of the above would more than likely cause the wall to move or fracture.
To render your wall with any of these problems having not been rectified you will waste your money rendering the wall.
Once you have fixed your wall or paid a pro builder to fix it for you you can render the wall but first remove all moss and debris from the surface with a wire brush
unibond the wall with raw unibond then bead all angles
and insert/fix 3m stop bead breaks along the wall these will allow you to rule off the wall on each coat of render. You need to apply a 1.5 sand cement render with feb mix 1st coat then scratch the surface ready for the next coat or top finish coat.
To apply this over the scratch coat i unibond this first
dependant on the weather conditions yes if its a hot day no if its a cold day. By applying the unibond this will give a key to the surface and will stop the render drying out quickly before you have floated and trowelled the surface.
So apply the top coat of render in 4:1 ratio building sand and cement with waterproofer 1-2 cap fulls per guage of mortar. Then apply over prepared surface rule off and leave to dry.
Keep checking the mortar over the next hour or so when your fingers no longer inprint on the surface its ready to trowel using a wooden/plastic float slightly dampen the wall flick water with brush and move the float over the wall right to left in a figure of eight manner once complete you should have no holes.
Next use a dry steel trowel ton the surface but this has
to be almost dry its important as you will leave trowel
lines behind as you move the trowel over the surface.
Remember before you paint the wall allow to dry 28 days
depending on the type of cement you used on the project
different cement applications have different drying times.
Hope this help to find out more check my profile. I am trying out MY Builder.com which i have never used before as i am normally very busy.
Paul Milne Firstclassbuilder
Answered 31st Oct 2011
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