Full height windows water seal

[Kelvin]

My ongoing house build saga where nothing seems easy turns to the full height windows, sliding door and French Doors. 
 

Our foundation wall is rendered up to a render stop. The windows are fitted flush with the kit. This is the detail. My renderer chap is saying he doesn’t think this will provide a good enough seal and he’s suggesting some kind of flashing under the window and over the render. We’ll have a patio slabbed up against this. Heb Homes are saying this will work and is there standard detail. They have also suggested using an EPDM apron lapped under the window and down the foundation. They’ve had three goes at fitting these windows and they still aren’t right. Any suggestions? 

 

[saveasteading]

2 hours ago, Kelvin said:

some kind of flashing under the window and over the render

Sounds about right. 

It's amazing we have to make these details up to suit circumstances.

 

Can I suggest that you imagine the rain running down the window, and what happens to it next. There should be a drip from the sill or bottom flashing, but that doesn't seem to be the case. 

The inserted flashing or drip needs to be fully sealed in to avoid it sucking water in rather than repelling it.

Then you have to make it run or drip to ground, rather than dribble back or splash.

Then on the ground a decent slope away or a gravel drain to get rid.

 

Do you have some 90° flashings efta from the cladding? If you haven't thrown away the offcuts you could play around with them for a solution or inspiration.

[Kelvin]

I have plenty of metal left over from the roof that I’ve kept. The roofer is coming back in a few weeks to finish the rainwater goods so I could get him to make us a flashing for these three windows. 
 

My concern is this flush with the kit fitting as it means the leading edge of the windows are sitting on the edge of the foundation at the moment whereas this detail shows it should be over the edge of the render. I am at my wits end with HH and their builder. 

[saveasteading]

12 minutes ago, Kelvin said:

windows are sitting on the edge of the foundation at the moment

We had perfect and expert detailing, but the reality of timber tolerances and shapes caused some discrepancies.

That's the reality of a unique project in a field, built from products made from plants and the ground.

But steel warps in manufacture too, and windows are clamped and glued together then stiffened by gaskets banged in  by a man with a bit of stick.

 

Perfection is only available to someone who isn't really looking.

 

To get really paranoid we could look for the tolerance standards on masonry and in timber construction. But they are probably very forgiving.

 

Ideally you need a metal or plastic flashing with a single thickness to push into the gap, a right angle to turn it downwards, and a welt ( return) on the bottom as stiffness and to make a drip ( and to avoid a serrated edge to cut busy fingers or snuffling pets .)

It probably exists already as a upvc profile.

 

 

 

[Kelvin]

We’re going to patio up to the windows so it’ll be an L shape down the foundation. 

[saveasteading]

it’ll be an L shape down to the foundation.

 

 

Better to drip into air and run away. Otherwise this flashing is going to be permanently wet, and will rust away, even if galv and plastic coated.

Can you fit in a gravel strip at the edge of the paving?

[Dave Jones]

what is the window manufacturer design for the cill detail ?

 

They are the ones you will be claiming against should it go wrong.

[Iceverge]

The HH detail looks pants for both durability and heat loss. 

 

I would get very liberal with some high quality fluid applied sealant externally to those blocks, take it right down below the level of the floor insulation. 

 

Remember water must do down and out. 

 

Then get some XPS or high density EPS and secure it outside the foundation blocks and sill plate. 

 

Finally get a proper insulated aluminium sill like those used for EWI and hook it under the  bottom of the window bedded in some suitable sealant. Ooze it out and scrape away the excess to completely fill any gaps. 

 

Render the outside of the insulation or glue on some slates as impact and rodent protection. 

 

A gravel topped French drain to finish should keep the water and splashes at bay. 

 

 

 

Edited June 24, 2023 by Iceverge

[Dave Jones]

 

What is the manufacturers recommendation ?

 

You dont appear to have a cill on those doors. How is water going to be shed from them outside the build envelope ?

 

You can carefully lap a DPC tray but a load of hassle and puts you in the frame if it leaks. 

 

Get on the phone with the door/window supplier and ask for a drawing to follow so it it leaks you have comeback.

 

What we did with our bifold was have a normal 150mm cill then tiled (porcelain) over the top of the cill to give a level threshold, put an aco linear drain under the cill to takeaway anything that found its way there. Never leaked once in 5 years and only had a 15mm lip to walk over.

 

 

 

 

 

[Temp]

 

On 24/06/2023 at 10:04, saveasteading said:

Can I suggest that you imagine the rain running down the window, and what happens to it next. There should be a drip from the sill or bottom flashing, but that doesn't seem to be the case. 

 

+1

 

Normally there are holes and pathways built into tracks that route water down and out. 

 

Here is an example from another manufacturer...

 

https://www.iqglassuk.com/technical-advice/how-to-prevent-water-ingress-on-sliding-doors/s88710/

 

 

[saveasteading]

6 hours ago, Temp said:

Normally there are holes and pathways built into tracks that route water down and out. 

A very good point. Water gets through gaskets more than you would hope. It also gets in at joints in aluminium sections. Then it channels to the bottom where there may be a hole in the bottom section, perhaps with a plastic spout in it. That needs to be allowed to drip.

[Kelvin]

There’s no issue with the windows themselves. It’s how they are fitted and sealed that’s the problem. Nordan are visiting site next week to replace an IGU that the scaffolders smashed. I’ve asked them to look over the installation. Separately I’ve told HH I want them to provide a detail for the window install and for their builder to apply it. I paid them to do it so they can do it. 

[craig]

On 24/06/2023 at 07:01, Kelvin said:

My renderer chap is saying he doesn’t think this will provide a good enough seal and he’s suggesting some kind of flashing under the window and over the render.

 

I agree with your renderer. It might be their standard detail but is it the window manufacturers recommended detail? Needs a flashing to protect and deal with water run off to be honest.

[Kelvin]

I can’t see anything on Nordan’s website on how to detail this. 

[craig]

12 hours ago, Kelvin said:

I can’t see anything on Nordan’s website on how to detail this. 

 

What is the product reference? I'll see if I can find the relevant information. This document, doesn't have balcony door details, just window details. https://nordan.co.uk/flowpaper/Operations-Manual/index.html?reload=1620723728428#page=98

Edited June 29, 2023 by craig