Browse Forums Landscape & Garden Design 1 Sep 17, 2014 11:31 am I have spent the last few days going through the threads on here and seem to be getting mixed responses & answers to my main fear\question. I'm looking at a wooden retaining walls, my major concern is white ants and if treated pine\redwood\other options are treated against white ants? From what i have learnt from threads on this forum is to stay away from the big green box "treated pine", be prepared for some twisting and bowing and not to have 2.4 meter lengths. If the wooden retaining wall options don't stand up well against white ants, I will have to go the cement sleeper look. Thanks ST13 Re: Wood Retaining Walls vs White Ants 2Sep 18, 2014 2:50 pm I'm no expert but I'm building H4 CCA treated pine retaining walls and I know I have termites in this area. If I leave untreated timber on the ground it is devoured within months. I've had part of my retaining wall built for about a year now and I'm not aware of any damage. The treatment must be H4 (or higher), H3 is not suitable if the timber makes contact with the dirt. As far as I'm aware the Arsenic in CCA will kill termites if they attempt to eat it (just breathing a hint of saw dust through a dust mask from treated pine almost kills me!). I've heard mixed reports on how long this can keep going for, definitely at least 10 years. Some say the termites will get through within 10-20 years, but elsewhere I have read that treated pine simply has not existed long enough for any documented cases of the treatment failing (50 to 70 years or something like that). When I have been concerned about cut ends of the timber appearing like the treatment has not penetrated far enough into the timber I have also wet the ends and then applied Hovex Termite Defender (from Bunnings insecticide section), that probably only lasts a couple years max though. If you wanted to be extra careful you could use a termite barrier (that orange stuff like Kordon). From what I'm told - even just being near it deters termites, so it doesn't have to be a perfect seal. I've never purchased it myself though, I imagine it would cost a bit to do things this way, and termite barriers are usually only used when building up against your house (like concrete patios and driveways). There is definite twisting and bowing in building treated pine retaining walls. Often the horizontal sections don't want to sit flat just because the timber comes all imperfect and wonky. Certainly making upright posts less than 2.4m apart (e.g. 1.2m) seems to help any bowing happening because of pressure from the backfill (proper drainage efforts with gravel and agpipe supposedly help, so I'm going all out on that). Personally I've been aiming for 2.4m which is almost never possible because of severely rocky ground, so I just pull it back and put a post wherever I can. I've also been screwing offcuts to the back of the wall to try and straighten and strengthen the spans, this doesn't magically help anything though - often the boards just don't want to straighten and the screws on the offcuts can't be tightened all the way. If you can afford the cement sleepers, and I suppose the extra precision it takes to work with them, it is probably better though The treated pine look isn't fantastic. I would consider cement sleepers in more visible areas, such as if you can see the wall from your patio. Depends if you like that look though I guess. I have considered 'dressing' my retaining walls with another type of timber (or something else?) - not structural... something that looks a bit better, and hides the inconsistency of the treated pine. This would probably be a lot more susceptible to termites, weather, fungus, bacteria, etc.. but it would be done in such a way that it could be replaced. Not sure if I can spend the money and time to do this though! Re: Wood Retaining Walls vs White Ants 3Sep 20, 2014 11:11 am Hi ST13, Samfordvalley is on the money alright and great treating the saw cuts - otherwise Mr & Mrs T eat the untreated par in the middle 75%, but worse still when they run out of food they start looking for mare and lo and behold there is your house. I believe that there are 3 timbers in Oz that are termite proof (may be wrong)... Turpentine (now rare), Bloodwood (now rare and sawdust deadly) and northern NSW cypress - available but usually used for verandah posts and stumps. Good luck retaining. There was an interesting yarn in central north NSW - Undarra - how mant trees around you have termites - answer all except that bloodwood over there... cheers Leonardo_23 We are tossing up between a Jarrahdale radiant wood fire (the Pioneer) and a convection wood fire (Innovator or Countryman) but cannot decide on which type of wood fire is… 0 5247 yeah i couldnt picture it issue either, but i could clearly picture what they were doing wrong haha 2 5289 Render your bathroom walls, two opinions versus the one, makes you wonder. 3 6045 |