Browse Forums Landscape & Garden Design Re: Retaining wall under patio slab 4May 10, 2023 9:54 pm Accessible Carpentry & Cabinets accessiblecarpentry@gmail.com accessiblecarpentry.com.au https://www.facebook.com/pages/Accessible-Carpentry-Cabinets/583314911709039 Re: Retaining wall under patio slab 6May 11, 2023 10:18 am Tetonsden chippy I understand your drawings are not structural drawings and only indicative of basic concept but it needs some refining. It's good practice for the top of any retaining wall to sit higher than what it's retaining so there is no possibility of earth escaping away and undermining the retained structure. Your top block should sit higher than the bottom of your patio slab. Then each of the retaining walls below should sit higher than the bottom of retaining wall above. You don't want any of your structures (slab or retaining walls) being undermined so it's critical that you get that right. In your example I'd be using a 500 high block at the top. Your sandstone block retaing is normally as many blocks deep at the bottom as it is high. So if it's 2 blocks high it will be 2 blocks wide at the bottom. If it's 3 blocks high it should be 3 blocks wide at the bottom. Is there a reference for this or a building/engineering guide that I can read into more about this? Reason I ask is that all the sandstone block retaining walls I've seen built have never been more than 1 course wide. The higher the wall the larger the batter angle I've noticed...which may be the reason why only 1 block wide is allowable? What you are building is called a gravity retaining wall. Gabion walls also use the same basic principles. If you think of a dam wall it's thicker at the base as that is where the greatest pressure is. The extra thickening of the blocks is at the back of the wall (under the back fill) so what you end up seeing is just a flat wall. The blocks you are talking about are very heavy and require lifting with a bobcat so are not diy. The contractor you get to do the job should be well versed in what is required to build a compliant wall This is a basic drawing of how a wall should look. Starting from the top you just come down however many blocks the height of the wall will be and that gives you an idea of how thick it should be. Notice how there is one block founded below the ground level to prevent movement. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ This is a picture of the back of a walk before backfill. Notice how it's thicker at the bottom. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Accessible Carpentry & Cabinets accessiblecarpentry@gmail.com accessiblecarpentry.com.au https://www.facebook.com/pages/Accessible-Carpentry-Cabinets/583314911709039 Yeah my reasoning is just that those house posts are designed for vertical load not lateral. I just didnt want to risk interfering with the existing house… 4 11645 Firstly the ableflex that has been installed needs (manufactures specification) a sealant cap over the top, preventing water draining down between the slab and the… 3 7979 Thank you again Simeon.. I will call my certifier for that. Have a good day 4 6077 |