Bungalow Renovation/ extension! - Hoping for high efficiency build

[boxrick]

 

New here... I posted once for advice but never introduced myself or got involved and it would be nice for bits of advice along my journey...

Some context, I live in the the Northwest of the UK. Have owned our 1970s bungalow since 2020 we never intended to move in, but due to ongoing ( even to this day, flooding, fire issues ) in our flat we moved to let work commence there. We had always planned to refurbish and extend this when we bought it but a number of challenges meant it never started primarily with bad architects.

 

Anyway fast forward to 2024 we have now a great architect and are in the process of planning things, we have incorrect planning permission and was going to apply for a modification then sadly in January 2025 our house was flooded

 

This meant we had to move out whilst it was being dried out, we decided to fast forward our building plans and applied for amended permissions.

The plans are to extend and completely gut the existing bungalow, leaving only the outside walls. New roof, windows, floor, add a bunch of rooflights ( 9 total ) to get light into the property. Then finish with MHVR, heatpump and underfloor heating. We will also be getting triple glazed alu-clad ( Norrsken / Fakro ) windows both on the roof and all round and having to take sensible flood prevention measures.

Many have asked why we didn't knock it down and re-build but ultimately that was just one step too far, we had so many decisions to make and keeping the footprint of the original building to work with just made one less major decision. 

Plans are broadly as follows, we will finish with around 115 square meters of house and will be looking to get external wall insulation. We are going to move the entrance to the side and our foundations need to be piled due to surrounding protected trees. 



 

 

Foundations were finished around the end of April and we have been building / stripping for around 2 weeks now.

A few pictures of the ongoing stuff, we started out removing a large tree.

 

Then I got a piling firm to build my foundations whilst I waited on amended permissions, I did this with the older planning permission

 

 

Sadly during this they managed to puncture the water mains which caused me a lot of stress....

Then I finally chose my builder and a few weeks later we got started with the drains

 

Then whilst we were waiting for signoff we started stripping the inside, roof ceiling etc

Then after we got the drains signed off, we backfilled. The beams arrived and the flooring built up in the new section:

Which largely brings me to where we were on Friday see this quick video:
 

 

Obviously a lot going on, and I am completely unexperienced at this. I have been trying to get numerous things changed in respect of thermal bridging, MHVR, external finishes, beams, getting electrics and water moved, gas capped off etc.

Right now I just paid for a Heatgeek to do a heatloss survey for my ASHP and underfloor heating based on my plans and intended build, my local guy seemed incredibly knowledgeable rather than the other people I have spoken to who feel more like salesman. Sadly they only seem to install Valliant ASHP. 

I am also trying to get a full sensible design for MHVR so it works well within my property. 

So right now I would appreciate any thoughts or input

- Is there anything sensible I should be doing in respect of extra measures in regards to flooding? ( We have raised the floor level and are concrete infilling existing property ) I will also be using things like anti-flood air bricks so any particular brand of that would be appreciated

- Anything worth doing in respect of the property in general, I keep hearing things like tanking being thrown around. Insurance is covering some general improvement works around the area and the flats so if I can bring anything up extra which may help me that would be useful.
- Any brand of ASHP I should be pushing for or looking at? 
- Whilst I am at this stage, anything I should be considering to include or modify on my build I may have overlooked? 

[Nickfromwales]

Hello...again!

 

Wow, a huge post and lots to see and discuss.

 

First question obvs is what is the flood risk? 1/100? worse? What caused the flood and when did it flood last? Useful to know before anyone can really comment, plus how high did the water get?

 

You're brave building (re-building) there tbh...  

[saveasteading]

It was an exceptional year for flooding, tho it may be that it happens again. What is the local view on it? was there an issue, eg blocked channels?

 

You seem to have been unlucky with the water height. 50mm lower and it would have flown past?  You could devise a set of removable dams across the outer doorways.

Basically a piece of ply into a slot then cramped to the wall, but other materials would be better.

At much greater expense and ugliness:  a wall surrounding the house, with a removable panel for  a gate.

 

Nothing wrong with Vaillant ashp as far as I'm aware.

 

[boxrick]

1 hour ago, Nickfromwales said:

Hello...again!

 

Wow, a huge post and lots to see and discuss.

 

First question obvs is what is the flood risk? 1/100? worse? What caused the flood and when did it flood last? Useful to know before anyone can really comment, plus how high did the water get?

 

You're brave building (re-building) there tbh...  

I didn't really have a whole lot of choice, our house would be worthless if we didn't. Luckily we are in a very good area and demand for houses here is high. Hopefully the measure we are taking will help mitigate future floods.

This spot has never flooded its a 1/100 year event, but obviously things are getting worse. In this case, the river broke its banks which meant it flooded worse than before and spread further. 

 

55 minutes ago, saveasteading said:

It was an exceptional year for flooding, tho it may be that it happens again. What is the local view on it? was there an issue, eg blocked channels?

 

You seem to have been unlucky with the water height. 50mm lower and it would have flown past?  You could devise a set of removable dams across the outer doorways.

Basically a piece of ply into a slot then cramped to the wall, but other materials would be better.

At much greater expense and ugliness:  a wall surrounding the house, with a removable panel for  a gate.

 

Nothing wrong with Vaillant ashp as far as I'm aware.

 

You could say unlucky, but honestly I have had a big payout from insurance. We have had accommodation paid for whilst we are doing our rebuild, so despite the stress of having to manage it all. Its been a blessing in disguise. We managed to move most of our nicer possessions onto worktops and similar.

I will get flood gates for our sliding doors / front door I think. 

[torre]

Does your insurer know of your renovation plans? Are they happy to continue cover and do you know what the premiums will be like? You're substantially enlarging the property (and their risk). 

 

How much are you raising floor levels? Every little bit will help. You mention options like tanking - you might want to look closer at these before rushing into further work that may make some measures more difficult to achieve.

 

If I were a future buyer I'd want to know every step had been taken to avoid future flood risk and even then, be mindful that inevitably a lot of buyers may be put off completely by previous flooding - that may limit future value and so (even if you plan to be there forever) perhaps bear that in mind when budgeting.

 

On a cheap, practical level you can get toilet bungs to stop flooded drains overflowing inside.

[ProDave]

You seem to be moving on with the mindset it was exceptional weather that caused the flooding and keeping FFL as it was.  I would not.  I would be looking for FFL to be half a metre higher and convert to a solid, not suspended floor so there is nowhere for water to fill up a ventilated under floor void.  That would of course require roof off and building up existing walls that may have tipped it towards knock down and rebuild.

 

I was reminded of this when away last week and we were in Stonehaven, and there were several houses all together up for sale.  SWMBO asked why that was.  I reminded her of Storm Babbet and those have probably all just been finished rebuilding after the flood and the owners want rid to some poor unsuspecting buyers who do not watch the news.

[boxrick]

39 minutes ago, ProDave said:

You seem to be moving on with the mindset it was exceptional weather that caused the flooding and keeping FFL as it was.  I would not.  I would be looking for FFL to be half a metre higher and convert to a solid, not suspended floor so there is nowhere for water to fill up a ventilated under floor void.  That would of course require roof off and building up existing walls that may have tipped it towards knock down and rebuild.

 

I was reminded of this when away last week and we were in Stonehaven, and there were several houses all together up for sale.  SWMBO asked why that was.  I reminded her of Storm Babbet and those have probably all just been finished rebuilding after the flood and the owners want rid to some poor unsuspecting buyers who do not watch the news.

 

In the existing property we are going for a full fill concrete floor.

 

The new property is on piles and is block and beam and it's all going to be a good bit higher too. 
 

Is there something else I can be doing beneath the block and beam before it gets fully encased?

[ProDave]

24 minutes ago, boxrick said:

 

Is there something else I can be doing beneath the block and beam before it gets fully encased?

I would say some vent holes at the lowest point, so if it does fill up underneath in a flood, the water can escape when it goes down, not remain and put pressure on the walls.

[boxrick]

32 minutes ago, ProDave said:

I would say some vent holes at the lowest point, so if it does fill up underneath in a flood, the water can escape when it goes down, not remain and put pressure on the walls.

We have exposed ringbeam and it's mostly bare soil with a membrane over the top.

 

At the lowest point we are already putting anti flood air bricks but this sit basically on top of the ring beam.

 

[Nickfromwales]

The measures for the new addition, FFL, should be repeated in the original parts. IMO it is crazy to rebuild with the known possible risk attached.

 

Is this a home for life or do you intend selling on eventually?

[saveasteading]

1. Try to stop water entering the void. Any airbricks vented up above flood level.

Tanking.

2. If it fills it must drain again quickly. 

So no solum membrane. 

Then it needs lots of ventilation.

3. Poly barrier between floor and flooring.

[boxrick]

54 minutes ago, Nickfromwales said:

The measures for the new addition, FFL, should be repeated in the original parts. IMO it is crazy to rebuild with the known possible risk attached.

 

Is this a home for life or do you intend selling on eventually?

FFL is going to match and be equal in new and old build. It was already around 70cm in height, we have further raised it as part of this renovation I think a further 10cm.

In respect of the re-build, we don't have a tonne of other choices. The building itself was very small so not attractive to either live in or sell. 

In respect of home for life... I honestly don't know. Will just have to see where the next years take us. Right now this is in a particurly desirable location, any other property of similar size or quality would be more or less double what I paid + rebuild. 

 

 

42 minutes ago, saveasteading said:

1. Try to stop water entering the void. Any airbricks vented up above flood level.

Tanking.

2. If it fills it must drain again quickly. 

So no solum membrane. 

Then it needs lots of ventilation.

3. Poly barrier between floor and flooring.

We are using anti flood air bricks which will have a channel right through to the void underneath block and beam, avoiding the cavity. Existing property airbricks to be removed as we are infilling with concrete. 

We already have a membrane here which was just laid on the soil as mostly a weed barrier. Should I get my builder to rip this out? Ventilation is up to building regs which is approx every 1-2m 


 

Edited 12 hours ago by boxrick

[saveasteading]

7 minutes ago, boxrick said:

Should I get my builder to rip this out?

My feeling is yes.  But welcome any other thoughts.

It can stay very wet in a damp basement for a long time/permanently.

 

i doubt the bco will agree because it is off the wall thinking.

 

what about forced ventilation? A fan system. Perhaps just build in a pipe sticking out of the wall (above flood level) that a suction pipe cold be fitted to.

Not that you will ever see in there again until the floor collapses.

 

anti flood air bricks  haven't heard of these. got a picture or link?

[boxrick]

15 minutes ago, saveasteading said:

My feeling is yes.  But welcome any other thoughts.

It can stay very wet in a damp basement for a long time/permanently.

 

i doubt the bco will agree because it is off the wall thinking.

 

what about forced ventilation? A fan system. Perhaps just build in a pipe sticking out of the wall (above flood level) that a suction pipe cold be fitted to.

Not that you will ever see in there again until the floor collapses.

 

anti flood air bricks  haven't heard of these. got a picture or link?

 

https://www.floodprotectionsolutions.co.uk/products/airbrick/?srsltid=AfmBOooX8CZN8nbIxS9IMB5RuO3GjgvpVdBLunvWpxD9GTruvOoCOYcP

 

Basically when it floods the little ball blocks up stopping water ingress.

[saveasteading]

20 minutes ago, boxrick said:

when it floods the little ball blocks up stopping water ingress.

You would need to keep that very clean.

No spiders, no lichen.

[Nickfromwales]

1 hour ago, boxrick said:

FFL is going to match and be equal in new and old build. It was already around 70cm in height, we have further raised it as part of this renovation I think a further 10cm.

In respect of the re-build, we don't have a tonne of other choices. The building itself was very small so not attractive to either live in or sell. 

In respect of home for life... I honestly don't know. Will just have to see where the next years take us. Right now this is in a particurly desirable location, any other property of similar size or quality would be more or less double what I paid + rebuild. 

 

 

We are using anti flood air bricks which will have a channel right through to the void underneath block and beam, avoiding the cavity. Existing property airbricks to be removed as we are infilling with concrete. 

We already have a membrane here which was just laid on the soil as mostly a weed barrier. Should I get my builder to rip this out? Ventilation is up to building regs which is approx every 1-2m 


 

If it owes you so little, then I guess it would be ideal to rent out as a retirement fund then. Doubt it would make any sense to sell / attempt to sell. 

[ProDave]

56 minutes ago, boxrick said:

Basically when it floods the little ball blocks up stopping water ingress.

Every time you see floods predicted on the news you see sand bags etc by the thousand.  I have yet to see a case where they do any good, and later you see the sand bagged houses pumping out the water.  You would need the whole house tanked to swimming pool standard for the outcome to be otherwise.

 

In the village I lived down south, there was one old cottage that regularly flooded when the river came up but not by very much.  They had "flood hardened" it.  The ground floor was quarry tiles on concrete with quarry tile skirting.  The walls were sand cement rendered to about 1 metre up.  No electrics were low down.  Kitchen units were on legs with no kick boards. When a flood was predicted all small stuff went upstairs, the sofa and other large furniture went up on bricks and the owner wore wellies when downstairs.  When the flood went, he just mopped out the ground floor and put the furniture back.

 

Perhaps a similar robust floor covering and skirting etc might minimise damage next time?

[Nickfromwales]

2 minutes ago, ProDave said:

Every time you see floods predicted on the news you see sand bags etc by the thousand.  I have yet to see a case where they do any good, and later you see the sand bagged houses pumping out the water.  You would need the whole house tanked to swimming pool standard for the outcome to be otherwise.

 

In the village I lived down south, there was one old cottage that regularly flooded when the river came up but not by very much.  They had "flood hardened" it.  The ground floor was quarry tiles on concrete with quarry tile skirting.  The walls were sand cement rendered to about 1 metre up.  No electrics were low down.  Kitchen units were on legs with no kick boards. When a flood was predicted all small stuff went upstairs, the sofa and other large furniture went up on bricks and the owner wore wellies when downstairs.  When the flood went, he just mopped out the ground floor and put the furniture back.

 

Perhaps a similar robust floor covering and skirting etc might minimise damage next time?

Depends on how high the water gets?

 

Oh, and f@ck that for a laugh, I couldn’t think of a worse way to live! Mopping Christ knows what contamination out and living with it…..🤢🤮👎

[boxrick]

So below the block and beam floor he has placed a level of visqueen which is basically an impenetrable plastic barrier. If I flood and it somehow gets into my subfloor, I assume this will simply gather water. 

Is it sensible at this point in time to get him to remove that and replace with some material which allows water to drain and then perhaps cover in a layer of gravel so it doesn't float? 

[saveasteading]

1 hour ago, boxrick said:

an impenetrable plastic barrier

the purpose being to stop weeds.  that should be completed by now.

Also to keep dampness down in the earth.

It is not intended to be flooded from above.

 

My hunch is that it is best to remove it, but what about  the bco?   the bco needs to see it in place as normal if they are to approve normal construction.

BUT we should not deceive the bco so I am 'writing aloud' not advising this....more research is needed.

 

My very old books show a layer of cinders or concrete instead of the plastic. That was never damp-proof but will have moderated seasonal changes.