How much technical detail should a construction drawing show?

[Adsibob]

I started a post a few days ago about what I thought was a faulty window leading to water ingress through  the top frame of the window, but after discussion with my architect I’m now realising this is more likely an issue arising from no weep holes being provided in the external skin of bricks linking to the DPC tray which I’m hoping was installed within the cavity wall above the window.

 

 The on site findings are that the screws screwing the window top frame into the lintel above have rusted, and water is entering the window frame via those screws. There is no issue with the window seals, in that spraying water directly onto the window does not cause water ingress. Some 45cm or so above the window, the external brick wall is showing brown discolouration in the mortar around a few bricks. The discolouration is quite localised and does not occur anywhere else in the brickwork of the extension (which is quite big), but this is the only place where we have a small cavity wall above an opening. The cavity wall above the large sliding door doesn’t have weep holes either, and the architect tells me that the reason there is no damp issue there is because there is much more space within the cavity for moisture to mix with air and evaporate. No idea whether that is right, but it at least sounds plausible, his theory being that no cavity will be perfectly moisture free, but weep holes are only required where this is a problem.
 

The construction drawings show DPC trays laid through the cavity wall at the top and coming through the outer skin of bricks, but that’s it. There is no further detail about including weep holes. There is also not a cross section of every new wall, so on our rear extension the cross sectional diagram shows the two side walls, but not the rear wall (which is the wall where we have the water ingress through the window problem). Is that normal? Or has my architect taken short cuts which have led to this omission?

 

 On the one hand, the builder I went with is very experienced and on the whole has done, or at least I thought he had done, a very good job, and I can see him saying that this is a design flaw, because the drawings aren’t detailed enough. But on the other hand isn’t this a standard construction detail, that any competent builder would know about? Surely cavity walls are bread and butter building work? What about the bricklayer and foreman (both employed by the builder) shouldn’t they have noticed the omission?

 

 Seems like a colossal f@ck-up!

[Mr Punter]

You need a cavity tray (DPC) and weep holes above the openings.  If there is a lot of brickwork above an opening on a wall that gets hit by the weather there will be a fair amount of water getting in.  If there is a tray you could just install some weeps.

[nod]

Whilst trays and vents should be shown on the drawing Brickies should No that they need to go in Weeps also 

I’m amazed BC haven’t picked this up on one of there site inspections 

[Adsibob]

6 minutes ago, nod said:

Whilst trays and vents should be shown on the drawing Brickies should No that they need to go in Weeps also 

I’m amazed BC haven’t picked this up on one of there site inspections 

So basically this is a mistake by everyone involved: the architect, the builder, the brickie and BCO. I really don’t understand what purpose BCO serve? They seem more nuisance than actual assistance. 

Edited October 26, 2023 by Adsibob

[Adsibob]

6 minutes ago, Mr Punter said:

You need a cavity tray (DPC) and weep holes above the openings.  If there is a lot of brickwork above an opening on a wall that gets hit by the weather there will be a fair amount of water getting in.  If there is a tray you could just install some weeps.

So is my architect just giving me false assurance that the bigger the cavity wall the less likely it is to need any weep holes? If so, I can’t explain why the small cavity wall above our window is visibly damp, whereas the bigger one, which is the same orientation, and just as exposed, looks fine.

[Mr Punter]

You could also coat the brickwork with Stormdry.  BC sometimes accept it if cavity tray is not practical.

[markc]

Also, screwing upwards through a window frame is poor workmanship especially into a lintel.

[Adsibob]

4 minutes ago, Mr Punter said:

You could also coat the brickwork with Stormdry.  BC sometimes accept it if cavity tray is not practical.

I wonder if that is what the "Alternative Approach" in section 5.6 of BR Approved Document C refers to, which states: "The requirement can also be met by following the relevant recomendations of Clauses 4 and 5 of BS 8215:1991". I tried finding that British Standards document "Code of Practice for design and installation of damp-proof courses in masonry construction", but I can't seem to access it without buying it.

 

If so, the builder definitely sealed the brickwork and mortar with a sealant, but I'm not sure what type was used.

 

 

 

[Adsibob]

1 minute ago, markc said:

Also, screwing upwards through a window frame is poor workmanship especially into a lintel.

Yes, I agree with this. What is best practice here? What should the window installer have done instead?

[Mr Punter]

10 minutes ago, Adsibob said:

the builder definitely sealed the brickwork and mortar with a sealant, but I'm not sure what type was used.

 

A type that does not work, it would seem.

[Adsibob]

5 minutes ago, Mr Punter said:

 

A type that does not work, it would seem.

I guess. Unless there is also moisture coming in through the parapet wall at the top, though there we have some plastic/composite coping stones and an overlapping membrane that came with a long guarantee, so seems unlikely.

 

i hate this sh!t. 

[kandgmitchell]

Well BS 5628 Code of Practice for the Use of Masonry says:

 

5.5.7.4 Weepholes
Weepholes should be formed through the outer leaf immediately above the cavity tray. These may be
formed in the vertical cross joints at intervals not greater than 1 m. There should be not less than two
weepholes over each opening.
Proprietary devices may be installed to form weepholes. They may be designed to drain the cavity but
prevent the ingress of wind-driven rain.
Weepholes need not be provided if walls have a rendered external surface finish.

 

I think this situation is frustrating for any customer of the construction industry. You have the designer, the constructor and the certifier and it still goes wrong. Part of the problem is every project is a "prototype". Another is the separation of the functions; in contrast for instance, a car company designs, sources and manufactures within it's own direct control. It then gets lots of goes at fine tuning the product to get it right. Construction tends to have different people who often don't talk to each other but nevertheless assume the "other" is looking after the detail. Once the one off build is done it's the customer who is left to find out what mistakes have been made.

 

How you prevent this kind of thing happening? Well the new Building Safety Act is a nod in that direction but I can't see this sort of simple error will ever be eradicated. It's gone on forever - they never did get that roof on Stonehenge despite getting the money up front!

[markc]

1 hour ago, Adsibob said:

Yes, I agree with this. What is best practice here? What should the window installer have done instead?

Best practice - no no top fixings (top hung rollers etc do require fixing to the support), definitely not through the frame, use straps to take fixing back to into the inner leaf away from cavity and any moisture. Don’t drill into lintels! If you go straight through a stone or concrete lintel then you can pierce the cavity tray and drilling into a steel (catnic style) folded lintel, these do collect condensation and you have given it a way out

[Adsibob]

Any thoughts on approximate cost to rectify this by:

1. inserting three weep holes, spaced 45cm apart above the window and inserting 8 weep holes, similarly spaced, above the sliding door (the cavity wall above the sliding has no damp at the moment, but I want to future proof); and
2. cutting out bricks to also insert cavity trays in a worst case scenario that this wasn't done either! 

In each case I suspect there will need to be some repointing done. If bricks break, I luckily still have spares. Though they've been stored uncovered on a pallett, and will be quite damp by now. Maybe I should bring a dozen into the house to dry them out for a couple of weeks?

 

I'm hoping only (1) will be required, but want to understand how bad (2) will be.

[nod]

3 hours ago, Adsibob said:

So basically this is a mistake by everyone involved: the architect, the builder, the brickie and BCO. I really don’t understand what purpose BCO serve? They seem more nuisance than actual assistance. 

Yes 

Your builder will argue that they have followed the drawing 

Who ever did the drawing should include trays lead work etc 

 

If your builder hasn’t put weeps in Its unlikely he’s put the trays in 

Get him back to put them in 

[LnP]

@Adsibob I understand why you feel sh!t about this. I've found dealing with problems like this causes me sleepless nights. Get the builder back and talk it through with him. It sounds like you have a good relationship and I'm sure he'll want to work with you to fix it. You'll feel a lot better after you've had that conversation.

 

I mentioned in your earlier post on this, that I'd had a similar problem (no cavity trays and other things) which was associated with water getting in via copings on a parapet wall. It required some dismantling and rebuilding to rectify. My sleepless nights were because I thought it was a big deal, but the builder just said, yeah it's a couple of days work, I'll get it sorted. He said he'd pay for it, but I'm a softy and insisted on making a financial contribution. The project was based on time and materials rather than fixed price, which was cheaper for me but meant the builder had no contingency or profit margin for screw ups. These things happen and I thought we should share the pain.

[Adsibob]

2 hours ago, LnP said:

@Adsibob I understand why you feel sh!t about this. I've found dealing with problems like this causes me sleepless nights. Get the builder back and talk it through with him. It sounds like you have a good relationship and I'm sure he'll want to work with you to fix it. You'll feel a lot better after you've had that conversation.

 

I mentioned in your earlier post on this, that I'd had a similar problem (no cavity trays and other things) which was associated with water getting in via copings on a parapet wall. It required some dismantling and rebuilding to rectify. My sleepless nights were because I thought it was a big deal, but the builder just said, yeah it's a couple of days work, I'll get it sorted. He said he'd pay for it, but I'm a softy and insisted on making a financial contribution. The project was based on time and materials rather than fixed price, which was cheaper for me but meant the builder had no contingency or profit margin for screw ups. These things happen and I thought we should share the pain.

Thanks @LnP this is really reassuring. 
I think part of my sleeplessness was caused by the same worry you had, so reassuring to know that it’s not a massive task to fix - my builder likes to do things quite slowly, so what took your guy a couple of days will take my guy a week.

 

I think the other thing that causes me sleeplessness is he is just generally quite a difficult man to deal with. He hates any sort of constructive feedback, let alone me pointing out a mistake as bad as this. He gets incredibly defensive and starts blaming someone else. That’s basically his personality. Luckily, I’ve always been able to see the good in him, and so despite various issues over the past couple of years, we’ve never fallen out. It took me a while, but I eventually learnt how to deal with him. That doesn’t stop it being a difficult experience most times. So I guess I’m dreading the meeting as I’m worried this bit of feedback will be the final nail in the coffin for our relationship. I say that, because in the past he’s always had the retention payment to incentivise him to continue, but I made that payment some months ago, so there isn’t much in it for him now other than decency and pride. So I will just have to deal with him extra diplomatically and probably end up paying for some of it.

[saveasteading]

On 26/10/2023 at 15:36, Adsibob said:

really don’t understand what purpose BCO serve? 

They do spot checks,  more looking for general incompetence than detail. They couldn't possibly be bd responsible fof everything unless paid many times more. Have a look at your bco fee and see how many days that allows.

 

However much these things are annoying you, be aware that much worse is happening elswewhere, and often being spotted....

 

I was asked recently what screws to be used for windows to stud. I said stainless, but I'd never really thought about it and assumed window suppliers knew. I'm not so sure now, and I'm  finding it difficult to find out.

Shouldn't rust, should have flat backs? Should have wide heads to spread  the load. Must not touch the glass.

 

Architects should be safe to assume some competence in builders. Unfortunately that isn't always justified.

The alternative ends up being screeds of generic notes that nobody would read anyway.  

On 26/10/2023 at 17:18, kandgmitchell said:

Part of the problem is every project is a "prototype". Another is the separation of the functions; 

Absolutely. A prototype made in the rain and wind, often dealing with the previous trades' mistakes.

 

Usually a linear process. A bit like Chinese whispers. 

 

There is an easy solution, which is to engage a project manager from start to finish,  OR a  "design and build" contractor, OR somehow find a team that will collaborate at all stages.

 

That won't be the cheapest, but it may be best value.

[joe90]

Sorry to hear this  @Adsibob and the fact it’s causing you sleepless nights, however it’s fixable, keep that in mind. My drawings (I did them) showed  no weep vents but both I and my builder new they were required along with trays. See what your builder says and if he gets arsy let him go, if the trays are in (and by scraping mortar from joints you should find them) then putting weeps in Is dead easy, even if there are no trays it can be done, just might cost  a bit but what cost peace of mind eh?

[MJNewton]

On 27/10/2023 at 19:53, joe90 said:

Sorry to hear this  @Adsibob and the fact it’s causing you sleepless nights, however it’s fixable, keep that in mind. My drawings (I did them) showed  no weep vents but both I and my builder new they were required along with trays. See what your builder says and if he gets arsy let him go, if the trays are in (and by scraping mortar from joints you should find them) then putting weeps in Is dead easy, even if there are no trays it can be done, just might cost  a bit but what cost peace of mind eh?

 

Yeah, absolutely agree with this. Fitting weep vents is trivial, and even fitting cavity trays is pretty straightforward for a brickie. They get a lot of practice for retrofitting trays when building extensions so it won't phase them at all. 

[Adsibob]

update:

 

first two weep vents went in last week, final three went in yesterday. So we have 5 now, each one spaced about 42cm apart from the other, above a cavity that is about 165cm wide, so just within the NHBC requirements (not that my house was built to that standard 😂).

 

 Was a very quick job. Could have been done in half a day, but weather required a different timetable.

 

 Looks pretty tidy:

 

They also removed the screws that the window company has drilled upwards, and filled the holes with silicone. 
 

So fingers crossed that is the end of my leak. Let’s see.

 

Query what to do about the damp looking bricks. It is actually not the bricks themselves, but the off white mortar that has gone a bit brown around a few bricks above the lintel. Is there any harm in waiting till the wall properly dries out, I expect no sooner than April next year given we are this side of winter, and then addressing that?

Edited November 11, 2023 by Adsibob

[Marvin]

LABC window fixing requirements...

 

Fixing distances for uPVC windows and doorsets Windows and doors should be installed in accordance with the manufacturers instructions. Frames should be fixed in accordance with the manufacturers recommendations or, if no instructions are given, with the following guidance: Wherever practicable, the sides of the frame should be secured as follows: • Corner fixings should be between 150mm and 250mm from the external corner. • No fixings should be less than 150mm from the centre line of a mullion or transom. • There should be a minimum of two fixings on each jamb and sill, with intermediate fixings at centres no greater than 600mm. • If the head is fixed with polyurethane foam, then the fixings at the head may be as follows: a) Frame width up to 1200mm - no fixings; b) Frame width 1201mm to 2400mm - one central fixing; c) Frame width 2401mm to 3600mm - two equally spaced fixings. • Frames should be fixed either by galvanised steel cramps or by noncorrodible screw fixings to the surrounding wall. Note: These fixings do not apply to french doors, patio doors, or bi-fold doors. Manufacturers recommended fixing details should be followed.

 

 

https://www.labcwarranty.co.uk/hubfs/Technical Manual v10 Files and Images/Manual Sections/Section 8 Windows and Doors.pdf

 

However drilling a hole up into the lintel puncturing the DPM seems mad to me unless you use stainless steel screws and lots of waterproof sealant in the hole.

 

 

[Adsibob]

2 hours ago, Marvin said:

However drilling a hole up into the lintel puncturing the DPM seems mad to me unless you use stainless steel screws and lots of waterproof sealant in the hole.

Yes, it’s pretty maddening that this may have happened. I don’t know the exact design of the lintel and DPM but I understand it’s a lintel with an integrated cavity tray. Not sure exactly how deep into it  the screw went, as presumably the cavity tray is at the top of the lintel, and the lintel must be pretty thick given it’s holding up lots of bricks.

 

The window supplier was responsible for fitting, so it would have been their mistake. But it was compounded by lack of weep holes, which likely caused water to build up. The leak was not huge. Maybe 25ml of incoming water after heavy rain for many hours. So I’m hoping the weep vents will now allow the 25ml of moisture that built up to evaporate, but we shall see.

 

Wondering if I should invest in that stormguard product someone linked, think it was @ProDave. 

[Marvin]

These days you should know that you need a lintel above a widow and that it will need a DPM  and weep holes. I don't think that would be a detail an Architect would add in. 

 

https://youtube.com/shorts/pg_ozicK-Bg?si=eNzUMmrZQUR9YRVT

[Marvin]

LABC info dated October 2021 about weep holes....

 

https://www.labc.co.uk/news/installing-site-formed-cavity-trays