How a dormer loft conversion works
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- เผยแพร่เมื่อ 9 ก.ย. 2021
- How does a dormer loft conversion work? Where do steels go? How do you strengthen the floor and roof? Find out in this video about dormer roof structure.
To compare architect quotes I recommend ArchitectCompare geni.us/architectural
How do you support the dormer roof and floor to get the maximum space and headroom? In this video, a Structural Engineer explains how a dormer conversion works, showing how to support the roof and floor with steel beams, and how to get maximum ceiling height.
#loft, #attic, #structure
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How to support a loft conversion:
• How a loft conversion ...
*Disclaimer:*
I'm a chartered civil engineer with a specialism in structural engineering. None of the things I say or teach in my videos should be construed as 'advice', and you should always have your designs checked by a competent, experienced, registered or chartered engineer. - วิทยาศาสตร์และเทคโนโลยี
Honestly I can't speak highly of your presentation skills. Your knowledge is clearly up there with the best, However finding somebody with your explanatory ability and gift for explaining things in a lovely, simple, form has been impossible, until now.
If a mansard extension was required at 70 degrees, how can that be engineered. I thought moment connections would connect the roof rafters to the joists sloped at 70 degrees. How could the loads be calculated?
@@DavidClarkBell it's Midnight David. Grab a pint or get to bed. It's a call you can make to the Engineer Monday 🤣😁
I am an Architect & Builder. This is very informative and very clearly explained, thank you.
Excellent simple guide to the key elements of a loft conversion. time to get the calculator out and watch the beam calculation video 😀
I think you have the best channel for timber and steel residential structures
Thanks Asim - much appreciated!
Much appreciated. I have my first dormer project as a graduate engineer and it's very insightful to see you break down the load transfer. Will help me for marking up with the racking panels and doubled up rafters where you indicated
Thanks Jake - glad you're finding it useful!
You're videos are amazing. Thank you.
the sketchup presentation really explains everything.....thanks!
This is so spot on for the project at my daughter's house which I'm preparing for. The combination of detail with simplicity of explanation is breathtaking. The software used is so versatile and adds such a dimension to Robins skill at breaking down a complex set of processes and bringing them within reach of a competent DIY-er such as myself. Many thanks; so helpful. Peter from Liverpool
Hi Peter - that is very kind of you to say!
Best videos here lads i m highly impressed
Great info Robin. I am currently planning a dormer loft conversion. This will be extremely useful advice. Thank you!
Glad it was helpful Martin!
Love the channel, thanks so much!
Fantastic presentation ❤
Thanks for posting
Excellent. Thanks
✅For a loft conversion remember you need an architect! I recommend getting quotes through ArchitectCompare geni.us/architectural
Well explained, suscribed
I love how you explain everything in detail❤️
I know that sometimes it's difficult to give definitive answer but I'm wondering if chimney isn't connected structurally with the roof (doesn't support any ridge or rafters) and it isn't part of the party wall (it's erected in the middle of the house) does removing this upper part (above the roof and attick section ) of the chimney requires any permissions or need to be surveyed by any official? 🤔
Hi Robert , What is the best way to support the ridge beam on a hip to gable loft conversion as the gable is to be built up in block work but if we built the gable , (mainly to support the ridge beam ) it wont give us much room to work around and give
us easy access to the loft space ? any suggestions please. Mike
Great video, really informative. Can you do a video with a double dormer, please?
Just a thought for a future video (inspired by your one on non former wide houses) - in the case of a house of the order 10 metres wide, assume the steel ridge beam would but unrealistically deep. In that case can any ideas be suggested for support from below e.g. two supports, one at 1/3 and one at 2/3. Also is there an option to angle these to the wall plate, rather than straight down. I'm assuming a loft split into three rooms rather than one large open plan space.
May I ask if you keep the pitch roof the thin rafter, how to do the pitcher roof insulation? I am facing the problem with my house. I opened the floorboard for the loft to gain a double storey space, but can’t do the insulation.
I have a terrace house and wanting to use the loft as a office / storage.
I have two roof perlings and two floor binders going into wall at each ends. I also have a v shaped support which is connected to the roof perling. I want to remove the central support to open up the roof space. I was told by a structural engineer that I can’t span from binder to binder as they not or can’t take the weight even though I said I would double them up with 7 x 2 and tie them into the floor binding. Also he said I needed ridge steel under the roof ridge ? He also said I would have to get steel x 2 to replace the floor binders and come off the vertical to the roof perling .. the question is do I need the steel for the roof ridge as I will be building a dwarf wall up to the roof perlings as I’m removing the central support
Hi, thanks for the interesting and informative videos. A non techincal person who is undertaking a loft conversion and trying to understand it all. Do you know what building regs sign off on ceiling heights as it seems such an unclear point on loft conversions? I also note that in this example the ceiling height will be sub 2m even with the steel ridge beam pushed up. You mention in order to raise the beam and fit the wooden dormer rafters from the steel that would be subject to certain conditions - what are those? Many thanks
Hi Robin. I have an outbuilding which was built about 8 years ago. The roof was engineered by a company and included an attick room. I am thinking of having a dorma to make more of the space. Do you think this would be an issue?
Hi, can i ask what might be the best roof for this design? I like your video.
Do I need a steel on the front wall or can I build of the the internal with a 4x 2 wall plate?.
Big thanks Robin for that. With a house about 5.5 metres front to back (and roof slope about 42deg) I'm thinking I'm a bit pushed for headroom so the extra floor steel idea is very interesting. The other bit I don't know how to estimate is warm Vs cold roofs. I guess a less desirable cold roof would give more headroom. That might make a good subject for a future video?
Thanks John! Yes, cold vs warm roof is a real head scratcher - hope to cover it at some point.
Is the side wall 5x2 on edge to have a space for the 4" insulation
Height being a challenge in loft conversions could you in theory reduce the ridge beam size by have an internal load bearing wall - the load being the dormer roof- near or maybe under the ridge itself.
How long would it take for this job to be done?
Also, how much would this level of work typically cost.
At the moment im not sure to have this done or not because i feel i really need to trust someone to do that level of work to the house structurally.
Within the width of the dormer, is the structural function of the joists limited to holding up the ceiling below?
Is it necessary to sheat the sides of the dormer or can you simply batten and slate?
Excellent!
What software are you using there?
Great work... could I ask what the sketch program is called?
I love these videos. It's given me a boost of confidence.
What software are you using?
Hi. It's geni.us/sketchup
Thank you! I'm reverting back to Civil Engineering after working as a Chartered Accountant for the last 23 years!. What Software are you using?
Hi Robin, im currently developing a house and looking to extend and convert the loft into living space i was wondering if you could help?
What if your house is L shape you have 10ft ceilings and you want to convert only half of the front and half of the back can I drop my ceilings two ft down on these half so that I can have more height in the attic
LOVE LOVE LOVE your lessons! Harvard, Cambridge and the like should pay you to design engineering courses...it would increase graduation rates and produce better engineers!
This is so fun, you can’t know how grateful I am!
Quick question, do you have a lesson on how to figure out my roof pitch and how to increase my roof pitch?
I want to add a dormer but I don’t think I have sifficient pitch/head room.
THANK YOU! THANK YOU! THANK YOU!!!
Hi Carmen - that's so kind of you! Well if you would like to put in a word with the Dean at Cambridge, I will be happy to talk!
Interesting question. To increase your roof pitch you would first need planning approval in the UK, as you would be increasing the ridge height. Other than that, basically it is a total re-roof, with dormer one side and new pitch the other side, and then you would need to build up the gable ends a little. Hope that helps - I will keep it in mind for a future video. What headroom do you currently have?
Pitch is calculated by Tan^-1 (vertical dimension / horizontal dimension) if you have a scientific calculator.
Thank you! I’m going to do just that, I’ll write Cambridge, my alma matter, and a few other engineering schools a letter. If they want to offer real quality to their engineering students, they should hire you to develop lessons and teach too!
I’m across the pond btw.
Looks like I have between 22-27 deg roof pitch (5/12 or 6/12), is that too small for the loft or dormer?
Wow ❤
Hey Robin. This has been really educational, thanks.
I have an almost identical layout that I'm considering converting. Can you give any idea on minimum steel sizing for this example and how deep into the wall is required? I have 5.5m span between gable walls of brick construction with no cavity. Thanks. 👍
How do you hide the second beam that breaks up the floor span?
The first beam becomes part of the wall, but what about the second ?
This is so helpful, I'm about to embark upon my own loft conversion to keep costs down, do in my own time frame but off drawn up plans, some of it doesn't make sense, I'm looking to remove existing purlins in my 100yr old mid terrace that used to be two houses, so I have cross over points that are still supported by a deteriorating old dividing wall, the idea is go through the wall at what will become floor level with a flitch plate beam upon which do a supporting stud to the rafters then hopefully remove old purlins and upper wall This will be the existing roof side then dormer out the other side. I'd love to be able to lift the whole roof off to do new and install purlins, rafters etc but this will be further down the line due to cost. Your presentation has just made total sense of what I should be considering. One question is, do you think a flitch plate beam to be suffice for supporting stud to rafters? span is approx 6.5 mtr with the wall in the middle to offer mid support. I'd have to work out gauges of wood and plates, the current plans for the ridge alone propose 2x 300 x 47 c16 beams bolted together with flitches. I could go on but just wanted to say, think the info is great and would appreciate more advice on my project. thanks
Hi. If you need some specific advice or calculations do get in touch - but bear in mind it will cost!
Hi thanks for this video and your other videos too, i have seen alot of this in person but never understood it but it all makes sense now you've explained it so simply, one question I did have was how the new floor joists would attach onto the rsj if the joists have been lowered flush to older beams would a slot or notch need to be cut for it to sit onto the rsj? @11.08
Usually it would be a timber packer within the beam flanges, bolted through the web, and then joist hangers
Why not just have the floor and ceiling in 1? Have the knee wall act as a box beam and just double up ceiling joists to support floor load?
Really insightful video thanks Robin. Wonder if you could answer a quick question. New build house wanting rear dormer extension. Length of the house is about 9.5m any reason why the structural engineer I'm using is reluctant to use steel beams to support the roof? Is 9.5m too long and heavy to use?
Hi Darrel. If you think about the rule of thumb for steel depth as around span/15, you would get a beam of 650mm deep, which is huge. Ideally you would break the span in half with a supporting wall at midspan, or you might need to consider a truss instead. Furthermore, regs stipulate maximum open areas and wall lengths, so this may be in play also. Hope it hels and all the best with your project 👍
Hi Robin. Great video, very helpful and well presented. One question I have regarding the head height and introducing the 2nd RSJ - as shown in the video. Wouldn't the 2nd RSJ create a step in the middle of the room or would this RSJ be shorter in height than it shows in the video?
Also what are your opinions of ECO tuss? Would using eco joists for the floor joists mean we could omitt the RSJ in the middle if the roof and create better head height (generally speaking). Thanks.
I thought exactly that re the second RSJ. It only matters what height the timbers are if you can also lower the steel, which in this configuration (beam perpendicular to and above ceiling joists) you can’t.
From what I can see of Eco Truss joists, they appear to be quite deep. If they were available at 170mm I’d be interested myself due to limited head height. Thus far I feel flitch beams are the best option for me, with the old joists cut around the beams and refixed with angle brackets alongside.
Hi Robin great video. Would it be possible to omit the ridge steel and support the ridge with a timber truss or timber box beam as per the other video you have made? This would open up the DIY option further without having to crane up heavy steels into the loft.. I am exploring utilising internal load bearing walls to support a new floor below the ceiling to increase head height in the loft, ideally can remove the need for large steels and keep it down the timber route. Thanks
Hi Michael. A truss or box beam could work as long as there is the headroom for it, because they will be a lot deeper than a steel beam.
Nice video thanks for sharing. How would you support the ridge beam if your two gable walls are made from timber rather than brick? I imagine a steel posts of some sort fixed to the inner leaf of the internal blockwork but cant see how this would be stable.
If gable walls are timber, a timber post inserted into the wall might work, or sometimes the wall is strong enough already.
Thanks Robin for all your videos! Can you use a flitch beam instead of a steel beam for the ridge beam for the dormer? If not, what can be used instead of steel when there is a small awkward space or a lighter alternative?
Hi Harmeet. Flitch beams usually end up heavier than steel "H" beams. So the best way is to design steel beam with splice connections. I do those all the time for my clients.
This is so informative! Can you please tell us if the height of a gambrel roof can be raised either with a dormer, or by making it into a Gabel roof? We have a shed with a gambrel roof. But we would like to lift the roof line on the lofted portion for more head space. We're trying to figure out how that might work.
You will probably need ridge steel and purlins, but it very much depends on how much headroom you have.
Hi really interesting insight on this project, can I ask if im doing which I am a loft conversion, on a 1930 semi with a traditional roof. How would you deal with the different size rafters between neighbours and maintaining the same pitch line? the birds mouth would be deeper but would that weaken the timbers
Hi David. The original upper edge of the timber is maintained, and the deeper rafters sit lower into the roof space. The steels would sit below this new internal roof line, with some space for a birdsmouth, which would slightly weaken the timber.
We purchased a home and are the second owners leaving previous owners the original builders. They had 20 years ago also added a dormer just like this to the original 1 bedroom upstairs area. It looks very similar to what you have at the end of the video. However, the dormer has a small sloped roof( not flat) and ends 6 feet or more before the back frame of the house. Directly below where the decided to end the dormer is my kitchen with a massive 3stacked plated wood header. Would it be possible to extend the dormer to the end of the 1st floor framework and be able to get rid of the huge header and if so what would that require of us ? Also would this option here provide opportunity for front dormer as well? We want to maximize space atleast one of the two options but both ideally if realistic. Which of the two would be the best to start with? Thanks again! Very explanatory
Hi Tessa. You could possibly do this, but it might be an almost total re-build of the loft.
Great video, we have just taken on a similar project and the engineer has done this with flitch beams and not steel beams/column? I’ve not done one this way before so is tricky to get my head round
Thanks Shane. Yes, flitch beams are very useful because you have two timber faces to connect rafters to, so it has the convenience of a timber beam with the strength of steel.
Great video! If it interests you and you get a cchancecoukd you do one on a hipped roof to a gable end with dormer loft conversion? Thanks!!
Thanks Tom - will keep it in mind.
Hi robin, I don't quite understand the reason why you drop the new floor joists below the top surface of the new steel beam when the floor will have to ride over this anyway? Are you expecting a step into the dormer?
Hi Guy. The steel beam is hidden within the stud wall, so there's no issue with the step. The other beam, at midspan of the floor, would be slimmer anyway as it is only taking floor load, and you are right - the floor joist would sit flush with this one.
Hi Robin. Great video. I was wondering if there is a way of having a dormer without the top steel. I’m trying to avoid using steels as I’m doing this job on my house alone and my home is a semi-detached bungalow so would like not to get a party wall agreement.
Hi. You could go with an LVL or Glulam beam.
Hi
I would like to know what force is on the ridge beam . I.E. A downward force or sidewards.
Could the ridge beam be pushed over when taking away the opposite side ?
John
Hi John. It would be pushed over if you loaded it one side only. The OSB / Plywood sheathing on the flat roof would be assumed to act against the horizontal force component when fully installed.
Really like your videos Robin. Wondering if you could answer a query about the RSJs in this configuration being fully restrained vs unrestrained? If I fill the floor steel web with timber and hang my floor joists from there, I would argue it is fully restrained. Would this be the case with the ridge steel, if the flat roof joists were hung in a similar way (not resting on top like in your video)? This would really help with calculating the buckling!!
Hi Michael. Yes, if the flat roof is sheathed in plywood or OSB then you could argue the beam is fully restrained.
@@RobindeJongh Good to have your input. I had a feeling I was going a bit over the top
Hi Robin, I have a traditional cut pitched roof, in which an internal load bearing wall runs through the centre from gable to party wall. Like in your video, the dormer will be to one side. My architect has indicated that a steel beam would run the length of the roof to support the new floor. Can the internal load bearing wall plate not fulfill this function and enable me to save some height on the pitched side? Perhaps dropping the joists between existing joists, from the centre wall plate to the purlin support?
Hi. The new floor could probably sit on the internal wall. However the roof needs to be supported too.
👏👏
Robin, I notice span tables only going upto 220mm...why is that? .... would it be possible, for example, to use 11 x 2 (279mm x 47mm) timbers..to have a span sufficient enough to not need steel at all?
Hi Lee. It's simply because these are the ecomomically available timber sizes.
Hi Robin, my architect says I won't need a middle beam as the spine wall is supporting. It's made of wood on the first floor and brick on the ground, in your experience do you think these are strong enough?
Hi. A timber wall at first floor is generally not designed as loadbearing if there are roof trusses above. You would need to get the wall checked and calculations provided.
@@RobindeJongh Hi Robin, I don't have a truss roof but extra supports from the purlin going down to the spine wall to support the extra weight of the.concrete tiles. I'll get it checked as per your advice thanks.
If I had steels installed would the extra weight potentially cause issues with the foundations. I've got a typical 1910 end of terrace house, I think there's only a few bricks in the foundations? Thanks.
Nice video. amazing software, what software are you using?
Did you ever find out?
It's SketchUp Pro geni.us/sketchup
Interesting, both my neighbor and me, in our pre 1890's small terrace houses both have had loft conversions with stairs going up etc. We though putting a dormer conversion on the back sides of our houses to give us headroom and turn the spaces into more substantial rooms would be a good idea. However we've been quoted over £70k each, apparently new regs or something, trusses need to all be replaced, basically a new roof. Seems a bit crazy to me, surely it's possible to strengthen existing beams with steel plate or something?
Hey Mr Duck. Somethings wrong there. I can't comment on the cost, but you shouldn't need a full re-roof.
Thanks Robin, why not put the new steel beams within the existing ceiling pack the steel and put new timber joists in?
Hi Liam. You would need to cut through the existing ceiling rafters and risk disturbing the plaster etc - if I'm interpreting your comment correctly?
@@RobindeJongh Yes that's right. Would definitely help with the clearance issues. Also, those existing ones look to be spanning now 7-8m unsupported. Even with self weight and plasterboard they are probably deflecting too much. Especially if someone hangs a boxing bag from the joist in the room under or something 😂
@@liamodonnell9091 The ceiling joists are supported by the steel beams with joist hangers or truss clips.
I just finished my igcse and now I am attending foundation because I don't really know about what career should I choose. I would like to go to architecture but it's kinda hard and low salary. Recently I am researching about IT. can you give me some advice on it. And which college will be better for that 2 subject
Civil and structural engineering are a great career choice in my opinion. Software engineering also.
Could you explain the order of works please?
Can the entire rear side of the roof be removed in one go before starting to assemble the dormer?
Do you need scaffolding in neighbours gardens in order to add the sides to the dormer?
Hi Andrew. If you remove tiles from only one side of the roof you may cause instability. It would need to be supported first.
Any reason why the flat roof part, doesn't have an incline to help the rain flowing?
That would normally be done with firring pieces or else the ceiling would be sloped
@@RobindeJongh I see!, I haven't thought of that. thanks!
Hi Robin! What programme are you using for these drawings?
Thanks
I'd love to know too
Looks like sketchy
I meant Sketchup
Hi Neil, it's SketchUp Pro geni.us/sketchup
Is there a structural reason for not taking the dormer all the way to the eaves or is it purely one of aesthetics?
No structural reason.
are the steels inbeded in gables ?
Yes
What size steal beam for ridge beam and flidge beam
Hi Oscar. You will need a structural engineer to work out the size of steel beams.
I definitely would have dropped that steel into the existing ceiling joists. Would have been worth it despite the poss disruption to the ceiling below.
It's definitely an option, and depends on how deep your existing joists vs new joists are.
How can you join your loft dormer to your neighbours dormer ,please? There is not even one video explaining it..probably it would be a good opportunity to increase your viewers numbers too,Robin De Jongh,plus it would take out some of my enquires.
It would be quicker and simpler if you just took the lot off and put a cut roof on, proper joists and standard steel setup
Hi Chris. That would certainly be an option and it would be down to the client and Builder to decide what was going to be the most economical solution.
The EcoTrus system is far better in my opinion....
obviously no answer to my question ? bit sad really
Hi. Your comment is addressed to Robert, is signed off Mike, and is from someone called Carol, so naturally I thought it was spam 😂