What Are Cavity Trays & Where Are They Used?
ฝัง
- เผยแพร่เมื่อ 28 ส.ค. 2024
- What are cavity trays, do you need to use them and if so, where are they used?
Picture credit: www.cavitytray...
Roger wants to help everybody understand their house better and take care of all of those little jobs that have been bugging you.
Do you have something in your house that you want to get your head around?
Get in touch: skill-builder....
#KnowYourHouse #BuildingFAQ #Brickwork
===================================================
Skill Builder Link Tree: linktr.ee/skil...
Tell us what you like: skill-builder....
Get in touch, send us your pictures and videos: skill-builder....
Facebook: / skillbuilderchannel
Out of respect to our channel sponsors and the wide variety of people who watch our videos, we will remove comments that do not follow common standards of politeness and decency.
![[TH] VALORANT Champions Seoul - Grand Final - EDG vs TH](http://i.ytimg.com/vi/WvObMc9VelI/mqdefault.jpg)
This is becoming more like the engineering explained channel but for buildings. This makes me happy.
I hope he gets more wiews, Apart from somtimes shillilng a tool or product, I can't really say he has been wrong on anything. I'm not a keyboard warrior that would jump down someones neck if the lighting wasn't right, etc etc. But If a mans doing right then I gotta say top man. And Clevvit, I can't fault them appart from they didn't buy me a bacon sarnie.
Sirus same! Where’s our bacon butties lol... that said, if I met them, I’d probably buy them one, a small price for a lot of their info/knowledge lol
Sorry to be so off topic but does any of you know of a method to get back into an Instagram account..?
I was stupid lost the login password. I love any tricks you can offer me
@Gage Preston instablaster =)
@Westley Quentin I really appreciate your reply. I got to the site through google and I'm waiting for the hacking stuff atm.
I see it takes a while so I will reply here later when my account password hopefully is recovered.
Roger is a good teacher .
Stay safe everyone
Not being a builder I never knew about cavity trays. Long story cut short I had water coming out of the cavity wall in my garage and collected it in a bucket for years. A builder pal told me about cavity trays and I discovered the bricky had left weep holes, but when the Alpine render was applied to the outside they were cemented over. I managed to locate them and get the drill out the cement. Thanks for the video Roger, I'm sure it will help people like myself who are having the same problem.
Bloody cavity trays a right royal pain in the arse for us brickies . Awkward to retro fit and murder to keep clean on new builds but a necessity.
I have to say Roger that DPC idea over the steels is a cracking idea , thanks pal 🧱🙌🏽
I watched your cavity tray installation video> Thanks also for the Belgian brickwork recommendation, great information. I love a bit of Flemish brickwork.
@@SkillBuilder no probs , and thanks for watching 🧱👍🏽
I put a 3m RSJ into a sold 9’ wall with DOC over the top. Never had any problems in the 13 years I owned the place after doing the job.
@@davidelliott5843 👌🏼👍🏼🧱
If only you had done this explanation 5 years ago, great video! Having purchased a new build from one of the UK's largest builders with a bay window, or as we came to rename the bay 'The waterfall'. We spent our first Xmas with indoor gutters as water poured into the house with heavy rain. Months of debating why Cav Trays had not been used, Why outer bricks are porous, refusing to have waterproofing applied to the bricks, builders grinding out to push DPC in above the bay all efforts failed. Eventually, the outer skin brickwork was completely removed then Cav Trays installed with amazing results. Dry as a bone.
Wow! That is horrendous. I can see why they didn't want waterproofer. The problem had to be solved for good. How many other houses had the same problem?
@@SkillBuilder Seven on our small estate requiring full scaffolding, strip, trays then outer skin rebuild followed by a specialists brick painter to touch up the repair. Full re plaster in the room, new carpets, curtains. Nice on new 5 bed houses for the want of £50 Cav Trays.
Thanks Roger, I'm really enjoying all the Skill Builder videos mate. I am a mechanical engineer and office worker, but really I love practical work and would love to have been a builder! I do all my own house maintenance and improvements, but am quickly running out of jobs, so I might have to move soon! Can't get enough of the SB vids. Cheers to you and Robin.
I'm an electrician and I think that the more each trade knows about other trades, the better. Makes for a harmonious building site.
Excellent explanation as always Roger 👍 Very common issues with penetrating damp because of these defects regarding trays. It’s even more common now since cavity wall insulation gets introduced, especially on those old damaged bitumen trays... 👍
Love this, great explanation, I'm a multi trade op for the local council, this sort of video would be great to share with the office girls to expand their knowledge 👍🏻
This will be a great video to show Eastbourne Building inspectors
Told my builder what he did using HD membrane was ok
Having to redo myself now problem surfacing
I have to admit we have just had an extension done and the outside was coated with what is to me a new rendering product that i think you have featured in one of your videos,s comes in various colors but the point is they never put those trays in and i can really see why we ended up with various movement cracks in the bedrooms above,with just installing the steels let alone chopping out more for trays ,great vide0 ,thanks.
Thanks Roger. Great honest video. Could you cover sometime when retro fitting a tray the best ways to attach it to the blockwork side and how important that is. Please keep em coming.
Straight forward excellent explanation. Thank you so much!
This perfectly describes the problem I have. Roger explains it clearly and eloquently. Why didn’t I come on to this before! Thanks very much.
I'm looking to have an extension on my next house soon and this is massively useful so I can ask and understand the right questions. Keep it coming!
I was the BCO that mentioned the storm dry. Cavity trays are the most common thing to pick up at completion stage along with trickle vents etc. Thanks for the video and hopefully more builders are aware.
Using Water repelllent instead of cavity trays is bodging in it's laziest form I am completely surprised at Roger.
Absolutely YES. Please do continue these type of informative correct methods of executing building activities. I love the DPC idea, on the next one definitely DPC above the Steels. Thanks
Easy enough to make a tray out of a roll of 18inch dpc, and fold over your ends! Well explained for a plumber Roger 😜
In the simplest terms a wall cavity is a drain, problem arise when the rain in the drain hits a window head or an obstruction in the cavity causing it to bridge to the inside or as Rodger said retro fitting steel beams. 😁A good example of retro fitting cavity trays is on bricklaying with Steve and Alex
Have also seen Cavity Tray used after problems with large pane double glazed windows that have been put in with I-beams for lintels and they've started to rot out due to the water in the cavity. One property I attended a rain flooded kitchen (thought to be water coming through the boiler flue) it was actually an inch gap above the window where the beam had started to collapse and the 2 stories of brick above where only being held up by the 8 x 6 ft double glazed window.
Thanks for that Mark. As usual we are getting comments from people who seem to think that these problems aren't real and that large amounts of water are caused by leaking roofs. I think they just don't get out much.
Thanks Roger. I've learn something today. As to your ending....... please keep doing these 👍
Thank you. I am just a bit ashamed of my poor drawing skills but I will improve.
Good vid. Would be interested to see one where a new set of I beams are installed internally for a new downstairs extension showing the concrete seating pads, the packing between the top of steel and under brickwork and amended brickwork right to boxing them in.
Halilula finally someone who knows his stuff. I have commented on a lot of videos on here asking why they haven’t put cavity tray in over a RSJ above the roof. And also why the hell don’t they cut the cavity out between brick and block work to stop damp tracking across. Or at least cut a verticalDPC.
Waterproofing a solid brick wall can be a disadvantage sometimes.
There may be some small areas where the waterproofing didn't hit, or some proofed mortar comes away, etc causing some of the wall to absorb rain.
Then, because of the coating, it doesn't dry out, and damp patches appear inside!
The coating does not trap water so it won't happen. I agree that some of the older types did suffer from that problem. I have seen water run down the wall and run into a hairline crack in the mortar and cause dry rot.
@@SkillBuilder masonry paint is the problem rain gets behind it and the only way out is inside the building
@@SkillBuilder Not sure about brick, but best practice in traditional solid stone walls is to avoid any form of waterproofing , hence the use of lime mortars, lime shelter coats and/or Lime renders and lime wash. This is the main reason Portland cement mortars/renders is now generally avoided in conservation work (because of its adverse affect on the 'breathability' of the wall. However, Nigel Copsey, an all-round expert on lime mortars, has mentioned on a few occasions that in the past salt was sometimes added to Lime wash. This essentially creates a flexible waterproof coating because of the autogenitive nature of Lime . The wash becomes waterproof because the lime and salt molecules lock together. It's possible that a modern waterproof coating could work in much the same way, as long as it was flexible enough to avoid any cracking and/or pealing. The reason Portland cement and masonry paint are detrimental to solid walls is that the former cracks- which then allows water in but does not let it out again easily (so you get a saturated wall , and the later peals lets water in and you end up with water blisters on the surface of the wall and again a saturated wall. The physics underpinning modern cavity walls and traditional solid walls differs quite a bit and what might be best practice with one can be detrimental to the other, personally I'd be very wary of using any form of sealant/waterproofing on a solid wall.
This is a great video! Very well made and really informative
A cavity tray is a sheet of damp proof that's built into a lintel that crosses the cavity wall,that sits on the block work & brickwork with the cavity tray coming across the cavity slightly higher on the block work to the brickwork, with small plastic weep holes placed into the perps in the brickwork this allows for any moisture water to come down the cavity tray & out of the weep holes .
Thank you for taking the time to explain this Roger. A great video as always.
thanks Rogers found this video very informative and useful
Well explained , makes sense , I just upgraded my English here ..... cavity trays 🙏🏻
My mother’s house was built in 1900 with solid 9” walls - no cavity. The bigger snag was inadequate foundations that needed underpinning.
Another excellent vid. With the knowledge and wisdom from someone in the trade. Thanks, Roger
Please keep these videos coming thick and fast. Thank you
Great video Roger!My house doesn't have any, maybe it should as someone in the past extended just like you drew with the flat roof to the rear.I always wondered where they were used,why and when. Very interesting and practical, many thanks!👍
I LEARNED SO MUCH IN THE 1st 2mins MANY THANKS ROGER SO MUCH THANKS
Great info rog. Got an extension planned for next year, so these nuggets are much appreciated.
ive done the same roger.
ive made myself a gutter as a pecaution between the rsj's channeling out to the outer skin as my extension is set back on beams and the bottom half is flush with front of the house
Seen this on an expensive conservatory where the fit company when bust.
I recommended a local builder to fit trays.
I was called out as the glass roof panels had not had their retainers fitted. They obviously slid down leaving a 125mm gap at the top.
Haha, nice one Rog, your timing is impeccable! I'm a window fitter and have had to do a quick rethink on an unsupported head. The opening is 1800mm so a bit wide for an angle iron and the cavity tray exits into the bed joint one course up, right in the way as I'd planned to use an IG L11! The bricks are Midhurst Pinks and have the strength of meringue so I'm calling in a favour with one of my brickie mates!
A really excellent explanation - I've learned quite a bit from this. (And other SB videos.) Thanks.
It makes perfect sense to install a cavity tray where required and where safe to do so. Having said that, I have never retro fitted them in 35 years of being a bricklayer and builder, and I have never had any evidence of water ingress, further, if the brickwork is of Type F2, and a full fill cavity, then the likelihood of internal water ingress is extremely low, provided the mortar joints and construction are sound.
Great explanation of the requirements. Relatively straight forward on new builds, however, to install a cavity tray retrospectively above an extension roof is a non starter in most cases, as you rightly point out, to do so may weaken the structural integrity of the existing building. Cavity trays can be installed retrospectively, however, the work is complex and how many clients will be willing to pay thousands to have this work carried out? To install trays properly, you need access above the tray, to ensure no mortar droppings are left or end up in the bottom of the tray, also how do you ensure thermal compliance and fit this retrospectively, with minimal room to manoeuvre and install the components. Good to hear that Building Control have realised this and have agreed to a practical solution for everyone.
In many cases it is a day's work to retrofit cavity trays and, since it is only the external skin the structure is not compromised.
Absolutely fascinating explanation, thank you.
A technique I have used in the past is to set the internal lintel very slightly higher than the external one and used burn on roofing felt to create a gully which if on an external wall can be fed to weep points or if on an internal wall (as in the extension example), it can be tracked to the ends of the span and then via some kind of gully to the external wall. Love the vids Roger, always some good ideas to be seen.
Here's my view, my thumbs up and my comment.
Thanks AJ
I have never seen any water exiting a weap hole in my career as a bricklayer, I can imagine if I did the roof or window cills have perished. The NHBC website is a great place to find up to date regs with details diagrams
Presumably though they allow a small flow of air which for small amounts of moisture will keep things dry. They will prevent build up of larger amounts of water in the case of a leak above. You do wonder about them getting bunged up with dirt in the long term.
On modern sites they have done away with the air gap now. They inject the insulation in to the building because its cheaper. I do wonder what will happen in years to come to these houses
Another great and informative video
Great stuff. Now I need a lintel & cavity tray detail replacement video on Victorian pitched roof bay windows ... ;)
Love owt like this not in building industry but always good to know. Now show me how to do a loft opening enlargement video step by step.👍
If it helps, Ryan, I just did mine last week! Due to covid rules in Scotland, I had to do it all myself, and the new hatch and ladder were quite heavy!
Pretty much all the diagrams you find online are correct, put a couple of supports either side of the new hatch, spanning the beam(s) that aren't being removed, supporting those that are. Cut out the beams to the new hatch width plus the width of the new timbers (double up, two timbers either side, just in case), then slot in the new timber and either use joist hangers or long screws to fix in place. I did this before cutting the new hatch as the plasterboard was well supported and I found it less messy, but it wouldn't make a huge difference either way. I found it easier to cut the plasterboard to the new hole. A few lessons learned: make sure you roll back all insulation around the area first, as it really does get in the way. Check for any downlighting or wires in the new space (I had to move one spotlight and extend wiring around the new hatch. If you are moving lights or wiring, take the opportunity to add in new loft lighting if required, as you'll not likely do it later! I used a reciprocating saw to cut the joist, which was accurate and quick and allowed me to retain the plasterboard as mentioned. Take a couple of boards (scaffold boards, cut in 2 or 3 lengthwise are perfect) up with you and once you've rolled back the insulation, put the boards down to sit or stand on while you work. If you're on your own, remove the ladder from the new hatch to install, as it is much easier just to lift the hatch without the ladder. Expect some minor plaster repairs when doing the job, I had a couple of cracks to fill (all my own fault, but if you don't do regularly, just expect errors). Finally, make sure you charge your drill driver batteries, and make sure you have someone downstairs to let you out when you install your new hatch from above and find that it doesn't open from the top....
Good luck. It's not too hard, you'll be fine!
@@ricos1497 rhanks mate for explaining in detail what you did👍
th-cam.com/video/ijwIU6Y5T9c/w-d-xo.html
I like that idea with the dpc on the steels, what customer is likely to pay the cost of installing damp trays on an extension, its a big job
So well explained. Throwing a joke every now and then also makes issues raised on this channel easier to digest.
great video again,,,but also the bottom tray on the pitched roof can be a catchment tray with both ends blocked off with a weephole vent
some people need to give their heads a wobble if they think you are only smart if you have a degree. this channel is priceless.
Excellent, presentation. An actual mock up would have been good. We over across the pond that watch You and Robin have to put up with some questionable other standards but good building practice and compliance to building regs and standards, means good construction. Thanks.
👍, bloody good channel you have here Roger. Look forward to the next one.
Need one of these.. above a window lintel.. got a 1800 stone/rubble built house that gets hammered with weather during the winter months. Pretty impossible to install one, so just had it all repointed. 🤞 it fixes leak.
Thank you so much for this video. Have been chasing a leak and you confirmed my suspicions.
Glad I could help!
Great explanation, Roger. Steve and Alex did a repair job where the previous builder put in a solid aluminum lintel with no cavity tray. Ugh.
Another Rouge Landon explanation wee poles cor blimey 🤠
Rouge, I was using stormdry before you were able to screw your hat on.
I like this technical advice... so useful 👍
Thanks always full of knowledge and including techical details. Being an engineer even knowledgeable for me.
So nice of you
This is the content i'm here for. Nice one Rog!
once again I have learned something. thank you.
Excellent video Roger. Very informative mate! 👍🏾
Great video. Would love to see something similar for parapet joints
I will keep thumbing up and keep viewing. I will keep thumbing up and keep viewing.
:) Seriously, thanks for these videos, I've learned a lot, it's the sort of info that's not readily available for me.
All the best!
I love theses know your house videos. Good job Rodger 👍
Thank you Roger - Very useful
Excellent video, this is what happened our house,builder built porch,but never put cavity tray in, now water leaking through,very annoying ☹️☹️
Great video, thumbs up from me, more of these for sure.
Really enjoyed this one, excellent.
This is extremely interesting. We have recently had water ingress into a downstairs window in our 25 year old house. Looking at our neighbour's houses (they are an identical design) they have several weep holes in the bricks where the steel lintel is above the window. We have just the one, at one edge of the lintel....... I am wondering if this is the cause. I have ordered some Stormdry, which I am able to apply myself, and am hoping this may cure the problem as I don't really wat the hassle of getting the bricks taken out and cavity trays put in. I really appreciate this video, thank you.
Rog - this is brilliant. Many thanks for sharing your honest knowledge and experience. Love it. Cheers.
Great video
That was the fastest extension ive ever seen built !!
As a bricklayer I always wondered why there was a need for cavity’s trays.... I didn’t put them in mine as I’m still not convinced. I always put them in other peoples of course.
Another fantastic and informative video, thanks again Roger.
Great video Roger, upskilled for ever now re g4round floor extensions! Top video
Cavity tray sits with its lowest edge above the flat roof flashing. Probably three or four courses above the I beams. Rock wool cavity insulation is good stuff and it shrugs off water. But leaks through the external skin will drip through the insulation.
Brilliant explanation
Nicely explained Roger, thanks.
Many thanks for the info, stay safe, ICAN, cheers, Schnuz.
Really enjoy the videos very informative.
The way I do it is to put a pice of wide dpc through the top of the beams tight in the centre slack at the ends so water can run off like a gutter into the cavity it always worked for me bricklayer for 46 years
Good tip. Either way works because a channel will still drain to the ends. Like you say it needs a good run off at the side. I would say 300mm each end so it is clear of the opening.
Good explanation, the only bit you left out is if you've got blockwork as the outside skin and the renderer kindly fill over all your extendable weap vents 😂
Air gap in the cavity creates moisture which needs to be sent out of the cavity.
Thanks for this.
Thanks Roger, well explained.
Nice little group of videos layout, ur the best mate.
Excellent as usual...looking forward to many more of these
Hi Roger. Really clear explanation. What happens when walls have insulation in the cavity? Are the horror stories about insulation wicking moisture to the inside walls true?
Really informative - thanks 👍
Great explanation
I think anyone who builds extensions for a living hates these 😂 the type Xs are a nightmare going up a roof, good thing for me is I only got to pop five mins down the road where they make them, never ever had a problem when they’ve been installed though
Thanks for another clear explanation. I always thought a layer of DPC did the job like you said, but my brother in law showed me the architects plans for his new flat roof over his existing flat roofed garage, and the specification for "cavity trays" over the stepped flashings. That sounds an absolute pain to fit, and if there are no openings/doors underneath why bother? Its a gable end and the garage is accessed from the front by the existing roller door, and at the rear by the existing utility door.....or is it to future proof against new openings?
An insulated Catnic lintel and a stepped DPC over it would be the method I'd go with for window and door opes. But cavity construction is a bit outdated with the likes of SIP panels and external wall insulation taking over a lot where I'm from.
Good for smaller use for windows and doors, but as they only go to 4.8 metres long, which are as heavy as a steel 'I' beam, so for any larger up to 6 m 'major openings' they're not useable.
This opening up of the whole back of the house seems to be very popular these days.
@@thetessellater9163 there's always the extreme lintel which goes to 6.6m. Not thermally broken of course. catnic.com/products/lintels/cxl310
I feel I'm a builder now u saved me years ;)
Love your videos Roger, thanks for the great content. I think it was in the late 80s when my parents had there house cavity walls pumped with foam insulation (you don't hear of that any more so perhaps it was not a good thing to do). How would the foam filling affect the water penetration, would it help keep out water?
The foam is good if it is done right with no void but it required mixing on site and the dry fill is a lot easier
There is nothing improper about solid brick construction when you understand how they work. A 9" or thicker solid brick walls dries out between even the longest spell of rain because the brick and mortar breathe. What is not understood is that blocking up ventilation bricks and fireplaces combined with central heating and higher temperatures creates internal condensation, where warmer and moist internal air meets colder brick.
I'm not familiar with Stormdry but all walls should breathe so that rain can dry out and allow any escaping internal water vapour to atmosphere . Traditional 9" brickwork uses lime mortar for that reason (and others). I'd be reluctant to use any kind of sealer as any rain getting through it via cracks or other weaknesses would be trapped for longer and find another route out (through finishes potentially).
Cavity trays might be fiddly and awkward in some circumstances but that's how cavity construction works - to keep the rain coming in to a minimum and drain it out in a safe way.
Ohh!! This is truly helpful! I am 100% sure the builder of our extension has no idea about this even though he is one of the nicest persons you can ever find for building work. The person who recommended the builder to me also has a leaking problem in his extension. This video made me think about this potential problem and prepare for it in advance.
However, what happens if we apply something like a coat of polyurethane on the wall above the extension? Will that work?
Don't use polyurethane. I have used Stormdry to solve this problem and it works. The last thing you want it trapped moisture so using Stormdry from Safeguard Europe is a better bet. It isn't cheap but it works and lasts a long time.
@@SkillBuilder I just sent these TWO videos (this and th-cam.com/video/-eq5zNWnO8o/w-d-xo.html ) to my friend who has this problem with leaks in the ceiling of a house extension. The builder has been attending to that from time to time and checking what's wrong. I can remember them looking into this even last year but they never found the issue.
Really informative . Many thanks
How compatible is this with retrofitted cavity wall insulation? Do those little plastic beads block up the weep holes or hold on to the moisture?
BRILIANT Thank You !