To EWI or just to render.

[pauljos1]

Hi All, Im new to the forum and a house owner and not a tradesman.

We are having our windows replaced in the next couple of months and then we are looking to render the outside of our property in K-Rend as that seems the most talked about/best looking product these days. We live in a terraced house with a covered alley down one side of the property for access to the back garden with double brick cavity walls back, side and front second elevation and stone brick cavity front ground floor elevation and no cavity wall insulation in place.

A friend mentioned getting the house externally insulated as part of the re-render process so I looked into it and thought it might be a wise move to decide which rendering route to take as we can position the new windows in the openings accordingly and prepare correctly for a EWI installation if thats what we decide to do.

I made contact with a renderer I know. He has quoted me for just doing a straight re-render in K-rend HP12 and K1 and also a EWI with 50mm 'insulation clad board' and K-rend HP12 and again K1.

I know from reading through threads that 90mm is the minimum thickness to achieve the U rating but our renderer said we wouldn't be able to achieve 90mm because of the depth of the eaves so suggested 50mm instead.

After doing some of my own research here and on a couple of the manufacturers websites it has raised a couple of questions.

1) Our house has flooded previously in 2000 and came very close in December 2015 (about 4 inches below the bottom of the floor joists in the downstairs) so is EWI even a good idea?

2) Would it be better to look at cavity wall insulation instead? Maybe spray foam insulation as that is supposed to be good for flood prevention?

3) What is insulation clad board? Does that mean Phenolic? I know that doesn't go down well here but Kingspan seem to see it as ok to use...

4) K-rend specify TC15 if using with EWI does that mean K1 is unsuitable?

5) the back wall of our house sits massively out of plumb, I think around 2 inches over a 6 foot level. The windows and Bi-fold doors will go in plumb so if we went for render or EWI can the render be plumbed level too or not?

Sorry if I'm waffling I just want to be able to go to the renderer a bit more educated.

Thanks everyone

 

[Jgreenplastering]

Sounds like your renderer has little or no experience with EWI, I don't use k rend but k1 is the standard mono im assuming in which case it can't be used over EWI.

You want a grey eps board as your insulation, you can still use the 90mm as you will use verge trims to suits which should bring it out past the eaves but protect the EWI from water penetration.

2inches is a massive amount to overcome over 6 foot but without seeing things there may be a solution. Why is it so much?

Not sure about the flooding tbh, It can't be good for it but one of the more experienced lads will be able to shed more light on it!

Maybe get some quotes off others or get a spec from a manufacturer and they will recommend an approved installer




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[malc]

you have a lot of problems with your property.
as regards flooding, i would just go for a straight forward render.
the rear of the property, i would guess that the rear wall has not got much of a footing. do the neighbours properties also have this problem with the rear wall ?

 

[pauljos1]

you have a lot of problems with your property.
as regards flooding, i would just go for a straight forward render.
the rear of the property, i would guess that the rear wall has not got much of a footing. do the neighbours properties also have this problem with the rear wall ?

Hi Malc, Yes the wall isn't plumb but it doesn't show any signs of cracks in the plaster or external wall. The whole house isn't straight it all slopes backwards. For instance the floor slopes down from the front to the back of the house. The neighbour that doesn't have an extension does indeed slope with our house and the other neighbour I can't really get an accurate level from as the extension is in the way.

 

[Marshy]

Save your cash for a boat moored in your garden should floods happen and charge your neighbours to board and use facilities

 

[Dansouthcoast84]

as above you have not been advised correctly on materials per system.
ewi is a good system and depending on how bothered you are on upgrading insulation as to whether you go for a thicker insulation.

we do install a ewi system for unplumb walls as yours as it is an easy way of building out without adding alot of additional weight to the substrate.

i would look into how you could stop water reaching your house as no render will stop this.

cavity ins will no doubt become damp.

krend will withstand a flood to a degree.
ewi the same but there is a damp proof basecoat that can be applied below doc if you are worried water penatration.

ask for samples and costs and go from there

 

[pauljos1]

as above you have not been advised correctly on materials per system.
ewi is a good system and depending on how bothered you are on upgrading insulation as to whether you go for a thicker insulation.

we do install a ewi system for unplumb walls as yours as it is an easy way of building out without adding alot of additional weight to the substrate.

i would look into how you could stop water reaching your house as no render will stop this.

cavity ins will no doubt become damp.

krend will withstand a flood to a degree.
ewi the same but there is a damp proof basecoat that can be applied below doc if you are worried water penatration.

ask for samples and costs and go from there

Hi Dan,

Thanks for your help. Can you let me know the system you can use with out of plumb walls? Or is it a modification method to a regular system?

We have been given grants for various flood preventative measures like flood proof air bricks, flood proof doors and gates, sump and pump systems.

If I do go down the cavity wall insulation route it will be with closed cell injected foam as this has passed the flood resilience test and not with beads, fibre or other cavity options.

What is the damp proof basecoat you can use?

I know some businesses around where we live who have flooded numerous times have had some knind of flood proof system put on their external walls. Any idea what this might be?

Thanks again

Paul

 

[pauljos1]

as above you have not been advised correctly on materials per system.
ewi is a good system and depending on how bothered you are on upgrading insulation as to whether you go for a thicker insulation.

we do install a ewi system for unplumb walls as yours as it is an easy way of building out without adding alot of additional weight to the substrate.

i would look into how you could stop water reaching your house as no render will stop this.

cavity ins will no doubt become damp.

krend will withstand a flood to a degree.
ewi the same but there is a damp proof basecoat that can be applied below doc if you are worried water penatration.

ask for samples and costs and go from there

Hi Dan, Can you offer any assistance on what system you would use to level out the wall?

 

[flynnyman]

Hi Dan, Can you offer any assistance on what system you would use to level out the wall?

You could level of the wall with sand and cement incorporating a mesh before EWI.

 

[pauljos1]

You could level of the wall with sand and cement incorporating a mesh before EWI.

If it's out 2 inch over 6 foot it's going to be out over 4 inch over the height of the exterior wall which is surely too much to fill out with sand and cement and what implications does that have on weight on the structure.

 

[flynnyman]

If it's out 2 inch over 6 foot it's going to be out over 4 inch over the height of the exterior wall which is surely too much to fill out with sand and cement and what implications does that have on weight on the structure.

You will lose some on the scratch coat and fixing the boards.

 

[zolco]

If it's out 2 inch over 6 foot it's going to be out over 4 inch over the height of the exterior wall which is surely too much to fill out with sand and cement and what implications does that have on weight on the structure.

You could try bauwer light, which can be built up quite thick and has insulation properties too

 

[Dansouthcoast84]

Hi Dan, Can you offer any assistance on what system you would use to level out the wall?

sorry havent been on for a while

i would eps the wall. eps comes in incriments of 10mm so i would examine the wall with a plumb weight and find when it changes depth then change the thickness of board

 

[Pagey]

Isn't it nice though that a genuine member of the public has got a quote but has done some real research on what he wants and the ups and downs of each product some real good renderers on here that will give u all the advice you need

 

[pauljos1]

Isn't it nice though that a genuine member of the public has got a quote but has done some real research on what he wants and the ups and downs of each product some real good renderers on here that will give u all the advice you need

Thanks Pagey. I'm sure some would say nice and some would say that I should leave it to those that do it day in and day out but I genuinely take an interest in things like this and want to know how it works and the best way to go about it. Plus if you are knowledgable with tradesman I always think you're less likely to get a cowboy job.

The other thing I have been looking into is making sure these new windows and doors that we are getting installed get the best sealing they can. I've lived with draughty windows and doors for long enough now.

 

[Pagey]

Thanks Pagey. I'm sure some would say nice and some would say that I should leave it to those that do it day in and day out but I genuinely take an interest in things like this and want to know how it works and the best way to go about it. Plus if you are knowledgable with tradesman I always think you're less likely to get a cowboy job.

The other thing I have been looking into is making sure these new windows and doors that we are getting installed get the best sealing they can. I've lived with draughty windows and doors for long enough now.

It's your house end of day do what you want with it and good to see your researching properly but do take advice of ones on here who have commented as they do render on a daily basis