Design review

[pipedream]

Attached is the design iteration for my signoff, ahead of planning application from the architectural designer . 

Background - Its demolition and rebuild of a bungalow, we have been living for past 7 years. 
More details in my introductory post   https://forum.buildhub.org.uk/topic/20015-self-build-for-a-growing-family

 

Overall, I am really happy with what they have produced, it has been heavy guided by me. The hallways/gallery spaces could be more efficient, but I was keen on horse shoe shape because of privacy concerns from neighbours surrounding the plot.

There are a few minor adjustments internally, I can think of,  but it would great to get views / improvements from more experienced folk out here. 

[Mr Punter]

I like the design but it could prove expensive to build.  Have you had it costed?  It may be that a few tweaks before it goes into planning will mean you have something that fits comfortably in your budget.

[saveasteading]

1 hour ago, Mr Punter said:

few tweaks before it goes into planning

If money is no object then carry on and sort the details later.

Otherwise i agree that some details  could be looked at for buildability.

Your designer may have considered this, but more likely assumes someone else will make it work.

 

For example, diagonal wall oversailing rectangular shape below.

Flat roof....downpipes inside your rooms.At least ask your designer about rainwater.

[Iceverge]

I like it. 

 

Can you provision for a ground floor shower or a lift for less mobile occupants. 

 

Privacy in the snug might be compromised from the kitchen with the the glazing arrangement. 

 

Have you considered overheating with the large ESE window in the kitchen? 

 

Expensive and some tricky details, yup,  but if you're prepared these can be hurdled. 

 

Looking forward to seeing your progress. 

 

 

 

 

 

[pipedream]

Thanks for taking the time .

 

@Mr Punter , I was in two minds about QS. 
In the end with the designer we decided, if it was not blatantly out of budget, then best to wait and we see what planning will agree to.

 

@saveasteading good pointers. The over hanging first floor was a compromise after some deliberation.
Initial view was that, first floor front wall will be inline with ground. 
For various reasons, the master bedroom position is fixed. Which then means, in order to have 4 decent sized rooms on first floor, the master bedroom would have to loose en-suite or dressing room (a deal breaker for better half)

 

We then tried something like below, without as much steel involved. From a massing and aesthetic point of view the protruding first floor was clunky.
The overhang also removes the need for separate rain protection for entrance door and works better to reduce visibility of the second floor. 
 

Edited September 24, 2021 by pipedream

[pipedream]

The designer's view on cost was that, on its own, the overhang will not cause a significant cost increase.
In my mind ,I thought it will only involve two additional structural steel beams like below. The crosses are where a supporting beam could go , if the span requires it.  
I am all ears, if there are other cost implications, that are obvious . 

 

I did not check on the drainage, assumed that it will be downpipes on either sides, running into the surface water drain/ soak away. 
The flat parts are proposed to be green roofs so drainage will have to dealt with very well anyway.

 

@Iceverge that is good point about non-mobile occupants. There is a non zero probability that parents might move in at some point.  Never though of lift, as I thought it would be too expensive, but as you suggested, it will be good to see if can be provisioned should the need arise.

The sung will have curtains (not ideal ), but with little kids , at this stage its good have all round visibility. With the glazing, the desired effect was for the  little garden to feel part of the house. The initial shadow analysis, showed fair bit shading due to two wings blocking each other at various points of time and the overhang at he back helps. We need to look at it bit more carefully, if planning goes through.

Any specific cost saving measures or other suggestions are most welcome. 
I like the idea of green roof, especially as the proposed structure eats into the garden, also felt the least I could do for the neighbours on that end, but I am concerned that I am setting myself for a leaking roof .
 
Any experience, thoughts on green roofs.
 

Edited September 24, 2021 by pipedream

[Ferdinand]

How close to the pavement are you? Can you do all your maintenance without the buggeration of scaffolding licenses? (One reason why as a LL I like terraces with small front gardens - solves the dustbin storage problem and keeps the *&^%$ Council a few feet away).

 

Green roofs only create the embedded carbon once, AIUI. Unless you propose to develop it into a mini peat-bog.

Whilst eg solar panels prevent a new set of emissions every year.

 

(?)

 

That's a rapid contra-thought which needs to be nuanced.

[pipedream]

2 hours ago, Ferdinand said:

How close to the pavement are you? Can you do all your maintenance without the buggeration of scaffolding licenses? (One reason why as a LL I like terraces with small front gardens - solves the dustbin storage problem and keeps the *&^%$ Council a few feet away)

 

I think so. the closest bit is 80cm to 100 cm away .Rest is good 4.5 meters away. The first two attachments on the original post gives an idea although dimensions are missing. Where i suspect we would struggle with scaffolding is the kitchen wing where the proposed structure is abutting neighbour's garden  (I own the boundary fence).

 

I see what you mean with solar panels vs green roof. I am doing more research   

https://www.theecoexperts.co.uk/solar-panels/green-roofs - This is more predictable argument in favour of solar panels

https://www.fmlink.com/articles/the-debate-green-roofs-vs-solar-panels-part-2-of-2/ - Bit more nuanced, favouring intensive green roofs over solar panels. Mine BTW is extensive roof and a weaker contender, but some points apply.

 

For me primarily 

- Its less abrasive visually than say flat GRP roof,  especially for neighbours who are exposed to this from rear facing first floor and loft windows.

- Helps with my suds 

-Virtue signalling to the planning dept, hoping it goes well with the theme that the replacement has better structure than one it is replacing.  

 

 

Edited September 24, 2021 by pipedream

[ETC]

Not that keen on the 45 degree angled walls on the ground floor.

 

Have you spoken to Building Control about the Kitchen being open to the circulation access to the first floor - staircase discharging into the Kitchen. It wouldn’t be accepted where I am especially with the staircase serving three floors.

[Mr Punter]

12 minutes ago, ETC said:

Have you spoken to Building Control about the Kitchen being open to the circulation access to the first floor - staircase discharging into the Kitchen. It wouldn’t be accepted where I am especially with the staircase serving three floors.

 

I did not even look at this from a b.regs point.  You may need sprinklers throughout and enhanced smoke detector coverage.  I have also seen automatic fire curtains specified.

[saveasteading]

Cosg of angle. As well as the steel beam itself, there is encasement and insulation of it, and the overhang itself needs detailing for being external...insulation and weatherproofing. A £5k detail at a guess, which might be worth it. I am not considering aesthetics and layout.

 

Green roof. NOHHHHHHHH.

Architect playing with your money. £5k again.

Adds 30kg/m2 to the roof loading. Needs maintenance..removing dead stuff and replacing, and for that consider accesx and safety.  Special roof membrane and lots of detail. And for what? Have a barrel instead.

[saveasteading]

1 minute ago, Mr Punter said:

fire curtains

£3k or more and not pretty.

[saveasteading]

And as a kitchen is a primary source of fire, perhaps not a great idea. Are there other exits...i have not looked.

Edited September 24, 2021 by saveasteading

[pipedream]

3 hours ago, ETC said:

Not that keen on the 45 degree angled walls on the ground floor

Thanks @ETC , I am struggling to figure out, which wall are you referring to .On ground floor all walls are 90 degrees or more. May be you mean first floor, due to the overhang,  the playroom and bedroom 3 have wall angles less than 90 degrees, but they are tad bit more than 75 degrees, practically should not be a problem.

 

3 hours ago, ETC said:

Have you spoken to Building Control about the Kitchen being open to the circulation access to the first floor - staircase discharging into the Kitchen. It wouldn’t be accepted where I am especially with the staircase serving three floors.

 

Just to be sure, are you referring to the two zones in blue below ? The centre points are  about 8 meters apart  . I didn't realise the open plan would be a problematic .It should be fairly easy to introduce a bifold door to shut off the kitchen wing. Do you think that will help?

 

[Dave Jones]

im not a fan of the canteen style setup, no separate lounge or dining room

[pipedream]

3 hours ago, saveasteading said:

Cosg of angle. As well as the steel beam itself, there is encasement and insulation of it, and the overhang itself needs detailing for being external...insulation and weatherproofing. A £5k detail at a guess, which might be worth it. I am not considering aesthetics and layout

 

Thanks that is very helpful helps weighing up the decision . 

3 hours ago, saveasteading said:

Green roof. NOHHHHHHHH

 

Thanks ,I was in two minds, now  I am seriously reconsidering. Also dread to think of consequences of any cockup in detailing of the roof.

 

[Gus Potter]

Hello Pipedream.

 

Wow! No wonder you're happy!

 

At first glance it may be worth looking carefully at whether this may be best build as a complete steel frame. The elephant in the room here is the global sideways stability of the building. On the ground floor you have a lot of glass, the building is U shaped, three storeys.. it will pick up a fair bit of wind load.

 

I would get an SE to mull this over before you progress any further. Make sure you get the stability nutted out as you don't at first glance have enough walls in the right place to achieve it without some complex bracing systems and associated foundations to "ballast" it. This means money and a fair bit of it too!

 

The above is not gloom and doom. You may find this is the most cost effective way. Steel is really versatile. For example you could look at a mixture of hot rolled steel beams ( the big I sections say)  and cold rolled floor joists and roof members. They are often Cee shaped (zed shape on the roof) and thin walled.. just the same as you see in B&Q holding the cladding or an industrial mezzanine floor. Oh and you will probably easily carry any extra wieght of a green roof to boot.

 

It requires a different approach (mind set) to the detailing in places.. cold bridging, insulation and fire protection but it's all doable. Cantilevers can often be more easily dealt with using steel, section depths are less and this allows you to more easily avoid "chunky" details and encourages more slender details for visual appearance.

 

Really what you do is design an "industrial building" as the skeleton and over clad. The steel frame is just a meccano set, quick to erect. Also, many of the weather proofing details are already developed, you have less issues with shrinkage cf masonry and timber.. plenty positives.

 

If you wish post more drawings. A good thing to do is put gridlines on the drawings if you can as it allows folk see at a glance how things line up between floors.

 

Al the best with what looks like a great house.

 

 

 

 

 

 

 

 

 

[saveasteading]

It seems to me that architects and planners have been sold that green roofs are great. They don't pay for or build or maintain them.

In my opinion, sedums have their places...some city centres, but mostly peat bogs.

[saveasteading]

5 minutes ago, Gus Potter said:

complete steel frame

As steel was my thing for some decades,  I agree. But I analysed a building not unlike this, but 3 times the size and chose to go with modular timber, just.

That is my hunch for this too.

Steel is not best suited to angles and curves.

 

Steel beams and perhaps columns will still be needed for this if in timber

Beware modular timber suppliers quotng "excluding all steels".

[PeterW]

Doesn’t meet Part M of building regs as on the ground floor you have to have an accessible WC and you have 3 steps. 

[saveasteading]

In case anyone is interested, i assessed in order of best value:

(Brick finish walls, mansard and flat roof.)

 

Modular timber

Structural steel

Modular steel

Trad masonry and timber

Modular timber/sips

Polystyrene system

 

 

 

[Gus Potter]

@saveasteading

 

You have hit the nail on the head here.

 

You can use them as as part of the "treatment train" for water run off and pollution manangement as per the SUDS requirements.

 

In lay terms.  Green roofs can hold the water for a while during heavy rainfall and then release it slowly into the eventual water course.. helps mitigate flooding. Water evaporates too (when it stops raining locally)  and so on so less ends up down steam.=adding to the flood volume.

 

Also, during dry weather air pollutants settle and get trapped on the growing matter. If you have tin roof and a dry summer you get all sort's on the roof from bird droppings to particles from car exhausts. If you get a short sharp shower of rain this all ends up quickly in the river which probably has a low flow so the concentration of pollutant is high and it kills the fish for example.

 

Green roofs can get you over the line for your permissions to build but saveasteading is right .. if you don't look after the roof, like you wash your windows or water your house plants it's all a load of.. guano / smoke and mirrors.

 

 

 

 

[saveasteading]

Comments are tending towards a 'wow' buiding rather than a buildable one.

Perhaps meet your designer and ask if building regs are addressed yet.

 

Some architects are more artist than practical, and leave someone else to make it work

[Gus Potter]

18 minutes ago, saveasteading said:

As steel was my thing for some decades,  I agree. But I analysed a building not unlike this, but 3 times the size and chose to go with modular timber, just.

That is my hunch for this too.

Steel is not best suited to angles and curves.

 

Steel beams and perhaps columns will still be needed for this if in timber

Beware modular timber suppliers quotng "excluding all steels".

And

 

11 minutes ago, saveasteading said:

In case anyone is interested, i assessed in order of best value:

(Brick finish walls, mansard and flat roof.)

 

Modular timber

Structural steel

Modular steel

Trad masonry and timber

Modular timber/sips

Polystyrene system

 

 

 

Great points, power to the elbow!

 

The thing drew my attention to the stability was the aspect ratio of the structure. Height to windward length.  In other words it is quite tall compared to it's footprint. There is also glass areas that would require some careful movement control not just in terms of vertical deflections but also horizontal deflections. Doing this in timber could be challenging when designing the connections to say the least! These types of TF connections need a lot of space which could destroy the Architectural intent.

 

If you look at the the walls facing the wind in the east / west direction there are not many in the "right place" of a decent length (without some fancy modifications) to resist the wind loading in this direction.

 

Now if we were to make the building footprint larger in the east /  west direction but no taller it would be more "squat" when considering the east / west wind and probably have more internal walls we could use to brace. This would then concur with the order of your analysis.

 

I agree that steel is not best suited to angles and curves.. in the round my feeling is that it is worth a close look at a steel frame on this project just to make sure you have not missed an opportunity.

 

Beware modular timber suppliers quotng "excluding all steels".

 

great advice from @saveasteading

 

[pipedream]

thanks @Gus Potter for the going into the potential pitfalls, structural considerations and suggestions. Its timely at this stage and I will pick it with the designer and SE depending on the outcome of the discussion with designer. To be fair U shaped building was my idea.

 

15 hours ago, saveasteading said:

Modular timber

Structural steel

Modular steel

Trad masonry and timber

Modular timber/sips

Polystyrene system

 

@saveasteading This and other pointers are very helpful.

 

@PeterW good spot, I had a read of part M and I will be taking it with designer also to double check on other provisions around the toilet sizes ,door and entrance clearances etc.

 

The kitchen /staircase location  should be ok (I think) as the snug glazing is sliding door and also the entrance does not really go though the kitchen. 

Edited September 25, 2021 by pipedream