Demolitions and propping for your home extension…… all you need to know.. how to do it

hi everyone have you ever wondered how steel beams are put into an existing house without the walls above falling down and who is it that decides how it's demolished now you may be thinking that this is a job for the experts the well-informed novice builder should stay well away well wait a minute here i'll go through the various options once you realize how it's done and how few tools are involved you might even realize you could actually do this yourself and first of all let's get the usual jargon out of the way let's talk props strong boys needles and structural engineers props are something that support the wall while we knock big chunks out of it in order to get a steel beam in the first type of prop is something called an acro prop and it's a steel tube with a flat plate on top and this can be adjusted in height using its own special extension system and whilst you can buy acro props a second hand i bought these two for 20 pounds you can also rent them for a few pounds a week for each acro acro props work in pairs to form a goal post arrangement along with something called a needle which is usually a steel box or eye section about a meter in length and as its name suggests it's used to thread itself through a hole in the wall you want to demolish supported on each side by our two acro props in order to create a sort of temporary goal post supporting the wall above whilst you take chunks out of the wall below the needle with your sledgehammer your structural engineer will give you the size of the needle and i'll usually get them supplied with the steel beam i'm ordering from my steel fabricator the second prop type is something called the strongboy and this is a steel l bracket and this bracket attaches to a single acroprop and works as a cantilevered arm to provide temporary support whilst you knock the wall below out and whether we like it or not for all of our projects in the uk at least we'll need a structural engineer's drawing and certificate in order to proceed i've talked about getting an engineer in my other videos so check that out in the description and knocking down walls of any kind within the house requires building warrant now whether to use strong buoys or needles with your props depends on the loadings the props are supporting and that loading is set by the weight of the structure above calculated as newtons per meter to get that you can ask your engineer and then you can go to your preferred prop manufacturer's detail to see the maximum loadings that the pro will take sadly all over youtube and social media i see examples of demolitions done for large rear extension openings such as this example here using just strong boys when it's clear that needles should be used i guess builders prefer these because there's less work involved in setting them up and it suits the owners of the houses since there's far less disruption to the house and because needles need to sit above the new steel beam for example in this case where the new beam is against the ceiling of the story above the needles and props needed to go through the floor and into the rooms above using strong boys would have avoided that so you can see the incentive of the owner to avoid the hassles of going through the floor and sealing now incentive or not if you use strong buoys where needles are required you and your builder will invalidate any insurance both for the homeowners and for the builder if there was any movement or worse a movement of any kind will result in all sorts of nasty defects and cracks as a rule of thumb you'll only ever want to use strong boys where the house is just a single story or where triangulation of the brickwork will support a small opening such as this new window but if you want to be objective you can go to the strongboy manufacturer's recommendation on the maximum loadings then search online for loadings for a typical two-story house get those loadings and you'll have your results you'll want steel needles acro props for anything where you're creating something as large as an opening for an extension and especially where it is two stories in a recent post in a home construction group i follow the builder proudly posted a shot of a large two-story house entirely supported using just strong boys and people posting concerns about not using needles were laughed down and why not nothing went wrong the steel beam was inserted and everyone is happy i won't tell you the many times i've heard a builder tell me about how the structural engineer knows nothing they over engineer it i've done loads of jobs like this since we're talking about posts on social media groups i guess i don't need to also mention the amount of really quite sad postings from customers photos of house extension disasters at the hands of a builder who has suddenly stopped returning calls these are some questions i might ask before i employ a builder on a large demolition has he got insurance is he insisting that you also notify your own builders as he should be because both insurance companies are involved for a project like this is he a limited company and if so what happens if he winds up his company when a disaster happens do you have a contract and if so what does it say about defects accidents and liabilities are you paying in advance and if so how much but none of these questions matter complete fuss about nothing just get on and finish the job in total harmony let's think of a scenario with your dream extension first time in several years big storm comes along in 1987 style gale force gusts strong boys can't take the horizontal force of the wind in combination with the downward force of the weight they're carrying and they collapse like dominoes now that's why we carry insurance right except when the loss adjuster forensically walks around the rubble of your collapsed house do you think he'll be unable to see that you have supported your home on strong boys and good luck with getting a payout from either your insurance company or your builder you will of course save some cash by avoiding using needles as will your builder i'm stating the blinding blindingly obvious of course this cash saving is only a saving until an accident occurs but i'll leave you to ponder any pros and cons of relying on a random builder dudes word over your structural engineers on what is most likely your biggest financial investment of your life if you can't afford to use acro props you're going to use strong boys instead just don't do the project the thing i really don't get is how simple it is to demolish a wall such as this correctly using props and needles even for you and me the well-informed novice self builder and why even considering shortcut in this part of the build is pretty weird given we are gambling with the most valuable asset we're likely to own in my next video i'll show you how easily to do both methods well thanks for watching and i hope to see you in the next one

Channel: Build Better Things

Views: 22,857

Keywords: steel beam house extension, steel beam house construction, how to install a steel beam, Rsj house extension, Rsj installations, Needles for steel beam, Acro prop, Demolitions, Structural engineer house extension, Strong boys for supports, Strong boy steel beam, House extension uk, House extension 2022

Id: C2UNJHhxeXo

Length: 8min 5sec (485 seconds)

Published: Sun Aug 14 2022