HOW TO UNDERPIN A BASEMENT - STEP BY STEP GUIDE WITH ENGINEERS PLANS EXPLAINED

Right. So let's talk you through some Right. So let's talk you through some underpinning.

So here you can see is a underpinning. So here you can see is a very general layout drawing that we very general layout drawing that we would receive um from a structural would receive um from a structural engineer which would show us what we engineer which would show us what we have to do to complete the pin within a have to do to complete the pin within a particular structure or a particular particular structure or a particular building. So this one here shows us the building.So this one here shows us the layout, shows us the pin widths and then layout, shows us the pin widths and then we'd have a sequencing that we'd have to we'd have a sequencing that we'd have to follow on a on a different drawing.

Um follow on a on a different drawing. Um this just showing the layout here. If we this just showing the layout here.

If we move up to the top here, it shows us the move up to the top here, it shows us the size and the width and the depth of the size and the width and the depth of the pin that we have for each pin that pin that we have for each pin that relates back to a section in the drawing relates back to a section in the drawing there. So, initially we would dig down. there.So, initially we would dig down.

We would only dig the width of the pin. We would dig down to formation level We would dig down to formation level approximately 1 m from the wall to give approximately 1 m from the wall to give ourselves some working room within ourselves some working room within there. on here.

We would back prop and there.on here. We would back prop and support that with some plyboards or some support that with some plyboards or some temporary propping um in order to stop temporary propping um in order to stop any soil that we have dug away from any soil that we have dug away from caving in against the guys whilst caving in against the guys whilst they're working in the base in the pin they're working in the base in the pin there. So once we've dug down and we've there.

So once we've dug down and we've got to our formation level, we would put got to our formation level, we would put a 50 mil concrete blind down on the a 50 mil concrete blind down on the floor there to give us a nice clean area floor there to give us a nice clean area to work to and give us some good level to work to and give us some good level control for our uh reinforcement. Next control for our uh reinforcement.Next phase would be to tie the reinforcement phase would be to tie the reinforcement cage according to the structural cage according to the structural engineers drawings. Um it's normally a engineers drawings.

Um it's normally a rebar um loose bar or mesh depending on rebar um loose bar or mesh depending on what's specified but we make sure that what's specified but we make sure that the guys follow the particular drawing the guys follow the particular drawing for that particular job. Once we have for that particular job. Once we have the reinforcement tied in there and our the reinforcement tied in there and our reinforcement has started up the wall we reinforcement has started up the wall we can then pour that base allow that to can then pour that base allow that to cure and then we can start our works on cure and then we can start our works on the uh on the wall here.

So again, as the uh on the wall here.So again, as with the base, we would then install the with the base, we would then install the reinforcement in the wall section from reinforcement in the wall section from top to bottom, allowing us to then place top to bottom, allowing us to then place our formwork, be it timber or a our formwork, be it timber or a proprietary system, in front of it here proprietary system, in front of it here and mass pour the wall with with and mass pour the wall with with concrete. Good compaction with the concrete. Always use a concrete poker to concrete.

Always use a concrete poker to allow um the air that's trapped in there allow um the air that's trapped in there as we pour it to escape throughout the as we pour it to escape throughout the top. And once we've finished our top.And once we've finished our concrete pour, we then look at our dry concrete pour, we then look at our dry pack. So, we allow our water to dry and pack.

So, we allow our water to dry and then we have a 75 mil uh 50 to 75 mil then we have a 75 mil uh 50 to 75 mil sometimes uh dry pack section at the top sometimes uh dry pack section at the top here. That's our transition between our here. That's our transition between our new foundation and our old foundation.

new foundation and our old foundation.The dry pack is very important because The dry pack is very important because as this wall concrete dries, it will as this wall concrete dries, it will shrink ever so slightly and then we ram shrink ever so slightly and then we ram the dry pack in good and tight and hard the dry pack in good and tight and hard there um to allow for any of that there um to allow for any of that shrinkage to be taken up in the new shrinkage to be taken up in the new section of dry pack. This stops any section of dry pack. This stops any settlement within the old foundation as settlement within the old foundation as it as it relates to the to the new one it as it relates to the to the new one that we've poured underneath.

Um, and that we've poured underneath. Um, and then once we've done that, we'll move on then once we've done that, we'll move on to our next sequence pin, which would be to our next sequence pin, which would be probably one three or four sections away probably one three or four sections away from the pin that we've just pour. Allow from the pin that we've just pour.Allow everything to cure and go off properly.

everything to cure and go off properly. And then that's how we just rinse and And then that's how we just rinse and repeat around the rest of the building.