Window fitting starts on Wednesday: Damp steels

[Jilly]

I've chosen triple glazed Aluminium argon filled windows made by a local company for simplicities sake. They are reasonably priced compared the ones the self build shows, but they aren't up to the same fancy spec. I had agreed with the builder that he would do up to the superstructure and then go on to subbies. The carpenters seem to have half prepared the windows and the window people agreed to fit the windows and measured and quoted for supply and fit in this rough state. There is no sign of the builder this week, so I will have to hope the fitters are happy to be flexible. 

 

Some of the (grey)  lintels are are rusty so I've gone and bought some Red Oxide paint, but they must be rusty on the bits under the wood frame. Does this matter? Should the wood come off and it be painted? I can paint them as best I can tomorrow but bits will be missed. 

 

I've noticed that the corner steel has damp coming up from the ground where it's fitted (there will be a big corner window). The base of this doesn't seem to have damp proofing, and is lower than the damp proof in the walls, if that makes sense. It can't be moved so does this matter? Rust has appeared at the bottom (this was a red coated steel). (The bricks you can see are approx finished floor level).

 

I'm resigned that this steel and the lintels above are going to be a thermal break, but is there anything I can ask them to do to improve things (the builder vaguely suggested drilling holes in the supporting steel to fill it with foam, but I think that would be difficult to do and to know that it was properly full)? 

 

I might not sleep now, worrying about this steel rusting away at the base  ?

 

(Stable conversion of old 140mm block building for those not acquainted ) 

Edited December 14, 2020 by Jilly

[Russell griffiths]

Get that concrete smashed out, get it wire brushed down vigorously, throw the tin of red oxide over in the corner and get some cold galv paint, preparation is key don’t skimp, coat it up with cold galv. 

 

My corner post is full with foam on the inside and has 40mm xps insulation on the outside then an aluminium cladding to match the windows. 

[TonyT]

Yikes, that looks a bit rough.

Stevie Wonder building corporation?

[Jason L]

It will be good to try and wrap it in some thin PIR insulation and clad it with Ali flashings to match the windows.  But as others said get the rust dealt with first.   Can you get dpc taped to it,  to lap with the dpc under the frames and the floor dpm. 

[SuperJohnG]

You shouldn't ever drill holes in sealed box section. Water gets in and rusts it from the inside out. 

 

Filling it with foam isn't going to do anything either. Its air inside it, which is pretty much the same thermal conductivity as insulation.  So no win here.

 

Adding insulation around the outside of the steel will help for sure as will properly stopping any rust in its tracks by rubbing it down and painting. However also...don't get too worried its not going to rust and fall apart any time soon. 

[Jilly]

But the windows will be fixed by drilling into the steel, I think? 

[SuperJohnG]

I woukd have thought it was better to drill then into some wood. But maybe thats the norm? 

 

I am possibly being over cautious, but ots not something we woukd ever do from an engineering manufacturing point of view. 

 

I double checked on the air vs foam u value.  And I might be wrong in the not being worthwhile here. But I cant see it adding much value as the thermal conductivity of the steel is so high. 

[Jilly]

It makes sense tho'. I've emailed the photos to the builder and the window installer. The builder is letting me down with lots of little things like this. I'm trying to part amicably now the superstructure is done, but I have conscious incompetence for what's required next... Thank you for

your help

[ToughButterCup]

@Jilly, consider Zinsser paint for your steels.  

I suggest it because of the (advertised) 15 year maintenance cycle. Yes, it's very expensive: but over (say) a ten year maintenance period, it's probably worth it. 

[Russell griffiths]

I don’t see a problem fixing into the steel my corner windows are. 

The bracket for the windows is bent around the outside of the steel and then tex screwed in, this is then sealed with pu sealant and the insulation board over the top. 

 

 

[Russell griffiths]

 

This is mine screwed to the steel post, not a lot of chance of those holes comprising the steel post. 

40mm of xps glued onto the post on the outside with an aluminium trim over the top. 

[SimonD]

On 14/12/2020 at 19:03, Jilly said:

I've chosen triple glazed Aluminium argon filled windows made by a local company for simplicities sake. They are reasonably priced compared the ones the self build shows, but they aren't up to the same fancy spec. I had agreed with the builder that he would do up to the superstructure and then go on to subbies. The carpenters seem to have half prepared the windows and the window people agreed to fit the windows and measured and quoted for supply and fit in this rough state. There is no sign of the builder this week, so I will have to hope the fitters are happy to be flexible. 

 

Some of the (grey)  lintels are are rusty so I've gone and bought some Red Oxide paint, but they must be rusty on the bits under the wood frame. Does this matter? Should the wood come off and it be painted? I can paint them as best I can tomorrow but bits will be missed. 

 

I've noticed that the corner steel has damp coming up from the ground where it's fitted (there will be a big corner window). The base of this doesn't seem to have damp proofing, and is lower than the damp proof in the walls, if that makes sense. It can't be moved so does this matter? Rust has appeared at the bottom (this was a red coated steel). (The bricks you can see are approx finished floor level).

 

I'm resigned that this steel and the lintels above are going to be a thermal break, but is there anything I can ask them to do to improve things (the builder vaguely suggested drilling holes in the supporting steel to fill it with foam, but I think that would be difficult to do and to know that it was properly full)? 

 

I might not sleep now, worrying about this steel rusting away at the base  ?

 

(Stable conversion of old 140mm block building for those not acquainted ) 

Hello Jilly,

 

Mirroring the other comments, that doesn't look right. With our steel structure the steels to be installed below ground level were all specified (and supplied) galvanised and any steels installed below DPC to be coated with bituminous paint - our SE specified 'RIW Toughseal or equivalent approved.' For steel coating and protection, I've previously received very good advice from the technical department at Promain. Not cheap but their service for me has always been first class.

 

Your builder definitely has a remediation job to do there I think.

 

HTH

[Jilly]

Update: I'm a bit stressed. ..I didn't get these replies until after the job was done and it was too late...

 

I chipped the cement off as best I could,  cleaned the steel and painted with red oxide. 

 

However, the windows have been installed and there is a small leak at the bottom near this place, the fitters came back to seal again but its still leaking. They will come back (but Christmas is causing delays), and they are making an aluminium shroud for the outside. 

 

I didn't realise about the bituminous paint thing (which the structural engineer specifies when you look through the detail). 

 

OMG, I can see this is my fault. Because there had been so many little problems with the builder I had decided to ask him to stop at the superstructure and I would go on to subbies, but this has left me wide open to making mistakes...like this.

 

 

Is there some kind of desiccant that will dry this out? How can the steel be treated retrospectively?? Will BC make me take the windows out?? 

 

 

 

 

 

 

 

[Jilly]

If I get them to strip off the exterior corner insulation and bitumen it, will that be sufficient?

Edited December 30, 2020 by Jilly
grammar

[Russell griffiths]

Do you have a pic from the outside 

[Gus Potter]

Hello Jilly.

 

Hope this helps. I have put my thoughts in line with your text and in italic.

 

Update: I'm a bit stressed. ..I didn't get these replies until after the job was done and it was too late...

 

Don't be, there is often more than one way of looking at things, and, you have all the resources of BH at your disposal.

 

I chipped the cement off as best I could,  cleaned the steel and painted with red oxide. 

 

Good approach but can see how you may still have a concern.

 

However, the windows have been installed and there is a small leak at the bottom near this place, the fitters came back to seal again but its still leaking. They will come back (but Christmas is causing delays), and they are making an aluminium shroud for the outside. 

 

Maybe don't conflate the two things.. leaky windows with steel corrosion. Separate the two issues.

 

I didn't realise about the bituminous paint thing (which the structural engineer specifies when you look through the detail). 

 

Yes they do as this is a common approach when you design / convert a farm building or an industrial building.. we know that this interface between the column, ground level, foundations and walls is a tricky area to detail.

 

OMG, I can see this is my fault. Because there had been so many little problems with the builder I had decided to ask him to stop at the superstructure and I would go on to subbies, but this has left me wide open to making mistakes...like this.

 

No Jilly it's not your fault. What you are doing in my view is exhibiting a good understanding of the build process, identifying previously unforseen problems before they really become an issue, which almost always occurs on renovations / conversions seeking advice, then a solution.  As a further word of encouragement lots of companies would love (give their back teath) to have their graduate trainees exhibiting  / questioning matters as you are doing.

 

Is there some kind of desiccant that will dry this out? How can the steel be treated retrospectively?? Will BC make me take the windows out?? 

I hope the comments I have made above will give you some encouragement but now time for some substance! BC will accept a reasoned argument so no need to "take windows out" that is last resort stuff. But for all.. if you wind BC up then..

 

If any other members can chip in then thanks.

 

Jilly as I said above. Don't conflate the two issues. Your windows and doors should be drained with small drainage channels and outlets. The amount of water that comes out these will be small but if these are not located / working correctly this is more likely to cause a problem with the glass rather than the steel. I'll leave this to the other members to comment on.

 

I'll give up on the italic now.

 

Turning now to the steel corrosion and the fact that this is a conversion.

 

Often when you are renovating you have to take a pragmatic view. That post you have looks quite chunky. It also looks like an older type section. I suspect that the wall thickness of the post may be relatively quite substancial. The reason this matters is that the section can suffer quite a bit of corrosion before it becomes unable to carry the loads.

 

Also, the corrosion that is happening is near the end of the section, this is where the bending forces caused by the wind and so on are less. Think of it as a ruler getting bent, the wind sucks the adjacent doors/ windows out, they are attached to the column and most of the movement / bending in this takes place in the middle.. the bending forces are greater here in the middle of the post. At the top and the bottom the column carries more vertical load (also shear load for the keen) but a locally thinner section here can often cope with this and in Jilly's case this thinning is cause by the rust.

 

Yes that is a bit of theory.. but it's relevant. Simplistically when we design and consider older structures that have got a bit of rust on them we look at where the forces are. We look at the depth of the corrosion and reduce the effective section thickness in these places, then analyse that. Also, the rust provides a protective layer (sacraficial layer) that helps stop the oxygen getting to the metal that is still intact. We then look at the rate of corrosion and try and ascertain if this rate of corrosion will reduce the design life of the structure which currently for domestic housing is about 50 -60 years.. and that discussion is for another time.

 

Jilly. In summary you may best just to leave this alone as the more rust you scrape off and mess about with it the more harm you may do than good. I think you should make sure that the glazing folk have set up the drainage channels outlets the correct way. Make sure you channel any water from a patio etc away from the house.

 

If you wish and if you want to be sure you can drill a hole in the post to get the thickness (about 1/4 to 1/3 up the height of the column) , take some really good close up photos of the rust and so on. BH members will give you some pointers as to how you can check this out structurally / get an opinion on this. Also, take some photos and post a floor plan so that folk can see what this post is holding up.

 

All the best.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Jilly]

Thank you so much, that makes a lot of sense. I think this journey both makes use of and develops a lot of transferable skills! 

 

The window fitters clad the steel externally with 20mm (I think) celotex and ply. 

 

The damp visible internally I'm assuming is tracking in from poor sealing between the window and the steel, and there is some water collecting in the sliding door track, so I'll get the drainage channels of the window checked. 

 

it is however, highlighting my concern that the steel is going to remain dam at the bottom, so I'd like to way to rectify or at least improve it, as damp must (also) tracking up from the slab. It's also surely going to get condensation too when the building is heated? 

 

 

 

[Jilly]

This is the floor plan, you can see the main rectangular stable building, with a hayshed extension (I've had the foundations, 6m piles, done so far). 

Edited December 31, 2020 by Jilly

[SimonD]

Hi Jilly,

 

Not sure where you are with this now and whether you've made progress sorting it out?

 

It's difficult to be absolutely sure just looking at the photos but I think you may have a couple of issues. I suspect the damp you're seeing is more down to the window sealing rather than the steel.

 

Regarding the steels, I think you can remove what's there and paint with bitumen, even around ground level below DPC. It'll be a pain but it's doable, even with the windows in place.

[Mr Punter]

Can you make sure the end of the timber cladding are coated before they put the reveal pieces on please!

[Jilly]

Update: the window people are coming back with an aluminium cover for the corner, so when it comes off I plan to do the bitumen, although I suppose I could try to take it off myself and have a look and paint. I haven't paid the balance, so I know they will come back!

 

What should the timber cladding be coated with?

[Jilly]

Steel and window update: The window people finally came back to look at another problem, so I showed them the mould and got them take the cladding off so I can bitumen the steel. I also asked them to change the ply as it was swollen at the bottom. There is some rusty filings not sure where from, so my plant is to apply FeO paint. Should I ask for marine ply? I've got some tape, so I'll put that on when they come back and then bitumen. I'm thinking they'll want yo get do d and not let it dry tho...