Hidden Retaining Wall.

Shagsy · Jun 13, 2007 10:56 am

Hi, I have a low corner in the rear of my property that I wish to level but in doing so would mean dirt/clay would be pushed against a tin fence, hence, I need a retaining wall to avoid any rusting or bulging (Only about 2-3 feet of build up required). My query is, what would be the best and cheapest material to use, plus method, for the retaining wall as it won't be a feature but a hidden purpose (I have the metal support poles of the tin fence every 2.5 metres on my side if that helps).? Thanks, Shannon.

DeKa · Jun 13, 2007 11:03 am

I would use treated pine, as you can be sure it won't rot.
I would recommend using 200x50mm planks, and perhaps 150x75mm sleepers as posts. You don't say where you are, but if you're in Sydney go to Logs Galore: http://www.logsgalore.com.au/ and they can advise you further.

Shagsy · Jun 13, 2007 11:13 am

Thanks for the speedy response which pretty much confirmed what I was thinking. I'm located at Seaford Rise, South Australia (south coastal from Adelaide). I wasn't sure if treated pine might still rot? But if not, then it seems the most cost effective way to go too. Thanks again, appreciate it.

Cookiemonster · Jun 13, 2007 11:15 am

I agree.. treated pine.

Set posts in ground using quickset concrete. Ensure the posts holes are dug to a depth equal to the height they'll sit above ground. For instance if the post will sit 300mm above ground.. then you'll need a 600mm post, 300mm of which will be buried.

http://www.landscapesupplies.com.au are also good. Also in Sydney.

3timesbuilda · Jun 13, 2007 1:22 pm

I put some treated pine posts into the ground, 1 year later, dug them out - completely rotten. Your experiences may be different.

I wonder is using large paving slabs on their sides would work for you. yyou would need to find something to hold them up but should work quite nicely.

3xb

Cookiemonster · Jun 13, 2007 1:29 pm

Treated pine comes with different ratings.. just make sure you get the rating suitable for the job.

Googled this description of the different ratings -

The "H" rating for Treated Pine is an indication of the use to which the timber can be put and its resistance to rot and attack by termites or borers.

H1 products are for use indoors above gound. Typical use of H1 products include, framing, interior furniture and joinery. Resistant to insects other than termites.

H2 products are for use indoors above gound. Typical use of H2 products include, framing, interior furniture and joinery. Resistant to insects including termites.

H3 products are for above ground use outside exposed to the weather and dampness. Typical use of H3 products include, decking, fence pickets, fence rails, pergolas, exposed bearers and cladding. Resistant to rot and attack by termites or borers.

H4 products are for in-ground or ground contact use outdoors. Typical use of H4 products include, fence posts, sleepers, landscaping, garden edges and garden boxes. Resistant to rot and attack by termites or borers.

H5 products are for in-ground, in water contact and ground contact as structural support components. Typical use of H5 products include, retaining walls and building poles. Resistant to rot and attack by termites or borers.

H6 products are for prolonged contact with sea water. Typical use of H6 products include, piles, boat hulls, landings, jetty posts and cross bracing.

Shagsy · Jun 13, 2007 3:12 pm

Sounds like you have to be very specific with the pine rating in order to get something worthy, I'd say I'd be looking at H5 rating. I would hate to have to dig it all up again 5 years down the track, even 10 years would be annoying! Thanks for the info, hopefully the different 'H' ratings are readily available. Cheers, Shannon.

Cookiemonster · Jun 13, 2007 3:22 pm

If the ground is quite dry you'll get away with H4 treated pine. But for piece of mind I'd go for H5.

DeKa · Jun 13, 2007 4:03 pm

DO NOT go for H5 unless you're north of the tropic of Capricorn. You pay 20% more for the timber, and it's completely unnecessary. H4 is the grade for temperate climates (defined as all locations south of the Tropic of Capricorn (roughly Rockhampton QLD). That guide seems to be misleading...

Osmose Lifewood is a very strong named brand here in Australia - they define H4 a the right one to use : http://www.osmose.com.au/lifewoodcca.html

H4 is perfectly fine for the example given - I have sample pieces of treated pine H4 rated which were put into the ground next to a garden tap (frequently used to wash hands so always wet!). After 16 years we dug it out- it was as good as new (other than being dirty).

3timesbuilda, if your treated pine rotted, return it to the place of purchase. They will replace it - treated pine has a 30-50 year warranty depending on the brand.

Shagsy · Jun 13, 2007 4:40 pm

The Osmose site only mentioned retaining wall use in the H5 Level. A very helpful site though, hopefully I can match the grade/level/rating of wood required locally to where I live. Below is the Osmose H5 Hazard Level;

H5 Hazard Level
Exposure – outside in ground contact with or in fresh water. Conditions – subject to extreme wetting and leaching and/or where the critical use requires a higher degree of protection. Biological Hazard – very severe decay, borers and termites. Examples of Uses – retaining walls, piling, house stumps, building poles, cooling tower fill.

Thanks for all the responses, definitely helping out a heap.!!!
Cheers, Shannon.

DeKa · Jun 13, 2007 5:16 pm

You can always try buying H5 in NSW or even Brisbane. You'll find it's hard work (special order only and perhaps up to 6 weeks delay) as it is just not necessary.

H4 is all that's necessary I assure you.

Solid Thinking · Jun 15, 2007 7:25 am

RE: Treated pine post rotting in the ground,

If you are installing posts for any reason and they are going to be under ground level then the most important point is to allow the bottom of the post to drain. The post is going to get wet (rain,etc) and thats not a problem as long as it is allowed to dry out. If you pour concrete and cover all around the post then it will create a bowl and retain the water.

The trick is to put 70mm of drainage gravel in the post hole, put in your post and the pour in the concrete. Make sure you dont lift up the post when leveling it.

By doing this you will leave the bottom of the post free to drain any excess moisture.

Cheers,

John

Yak_Chat · Jun 15, 2007 8:16 am

Shagsy, As your in SA check out the Auspine range of products made at Kalangadoo.
They do a range of Creasote treated fence posts and their process includes pressure steaming the logs before they treat them.
ie they put them into a very large sealed container and presurise them at something like 300PSI and around 100 degrees C. The heat and pressure expands the tissues in the timber, the logs are then immediatly taken tot he creasote or CCA treatment and immersed to achieve a high penetration rates of absorbtion.
Re the fence, I assume this is your neighbours dividing fence, I'd make sure it is not all going to slide over to his side over time.
Thanks for the other info John.
Cheers
Steve