Building options for a 5 story block of apartments

cgarrad

Hi, Im going to build a 5 story block of apartments in the city centre.

I was going to use precast hollowcore floors on 9" solid walls.

I was wondering if any one had any knowledge of using structural steel with composite metal concrete deck?

Also open to precasting the whole structure with form work.

If any one has knowledge other options, of which would be best, and the cost difference between the various methods Id love to hear ;-)

Each floor will be 3000 sq/ft and it an L shape made of 3 equal boxes

Poor Uncle Tom

cgarrad wrote: »

Hi, Im going to build a 5 story block of apartments in the city centre.

I was going to use precast hollowcore floors on 9" solid walls.

For the whole 5 storey construction?

cgarrad wrote: »

I was wondering if any one had any knowledge of using structural steel with composite metal concrete deck?

Yes, it's an alternative to the precast floors.

cgarrad wrote: »

Also open to precasting the whole structure with form work.

This statement is confusing to say the least. Are you talking about casting floors off-site (precasting) and transporting them to site and fitting them?

cgarrad wrote: »

If any one has knowledge other options, of which would be best, and the cost difference between the various methods Id love to hear ;-)

Each floor will be 3000 sq/ft and it an L shape made of 3 equal boxes

This really is a specific one off job, for a team of professionals.
At what point in the project are you at? Design, planning, tendering?
If the overall structure has not been designed yet, then your questions are premature. The materials and methods of construction may go hand in hand with the design of the building. Have you chosen an Architect? Have you spoken to them about it?

dan_d

PUT makes good points.

What is your involvement in this OP? You need a team of professionals. I have been involved in a structure with steel and metal decking, however your questions are quite vague. It's not just a matter of cost, it's what you want inside and your method of construction (ie the shape of the building and the sequence of works) that will also dictate your choice.

When you say 9" solid walls - blockwork? All walls? What kind of cladding is there? Do you know how much blocklayers cost?What do you mean by "3 equal boxes"?

Those are just a few of the questions that arise from your question. If you haven't already, you really should employ a team of professionals - architect, engineer, QS, services people, etc.

De.Lite.Touch

cgarrad wrote: »

Hi, Im going to build a 5 story block of apartments in the city centre.

I was going to use precast hollowcore floors on 9" solid walls.

I was wondering if any one had any knowledge of using structural steel with composite metal concrete deck?

Also open to precasting the whole structure with form work.

If any one has knowledge other options, of which would be best, and the cost difference between the various methods Id love to hear ;-)

Each floor will be 3000 sq/ft and it an L shape made of 3 equal boxes

Cost difference is the issue here, but it centres on the design of the floor plate as much as the cost of contrauction.

3000 sq.ft. is 278sq.m. per "square" equalling sides of 16.67M
Natural light penetrates about 5-6M - with a corridor of 1.5M that gives a floor plate width of 13.5M maximum.
Most offices are that width and unless you have a brief to build the building that size your width seems too big.

Using an L-Shaped form creates an "elbow" which gets little light.
An 11M-sided "elbow" is a lot of space to fill with a reception with no views, loos, a lift and a stairwell.
Also if you have your stair in the "elbow" your single direction travel dstance of 12M is exceeded by nearly 100%.
You'll need three stairs instead of two.

So first, before you go anywhere near costing the structure, talk to a commercial letting agent about your floor plate layout and depth.
Then appoint a design team and see what they can bring to the table in terms of adding light and amenity to wide floors.
If they can do something, you may end up with a lettable building of that width.
The increased light levels will offset the depth and have a positive effect on the eventual sale or let.

Otherwise the extra width and the reduced light and amenity may mean the build could suffer by comparison - in a recession - and won't let or sell well.
You could consider reducing the floor width to increase its light and amenity and thus reduce the size and cost of the building.
Advice from an architect and letting agent may allow you ot do so without compromising its lettability and overall return.
Houses bear little relation to apartments in terms of service runs, access for services and fire safety.

De.Lite.Touch

cgarrad

Poor Uncle Tom wrote: »

Are you talking about casting floors off-site (precasting) and transporting them to site and fitting them?

About pre casting, it would be onsite.

Poor Uncle Tom wrote: »

Have you chosen an Architect? Have you spoken to them about it?

Not mad about taking an architects advice, (have you seen the building in this country ;-)), Id prefer a builders knowledge. I did plans about 3 years ago but the architect went bust, and emigrated ;-)

dan_d wrote: »

what you want inside and your method of construction (ie the shape of the building and the sequence of works) that will also dictate your choice.

The site is the same as getting 3 cubes and placing the in an L shape. Putting 2 bed apts, 3 per floor

When you say 9" solid walls - blockwork? All walls? What kind of cladding is there? Do you know how much blocklayers cost?What do you mean by "3 equal boxes"?

As regards brickies, thats why Im asking ;-) Pouring the whole thing could be cheaper?

De.Lite.Touch wrote: »

Cost difference is the issue here, but it centres on the design of the floor plate as much as the cost of contrauction.

3000 sq.ft. is 278sq.m. per "square" equalling sides of 16.67M
Natural light penetrates about 5-6M - with a corridor of 1.5M that gives a floor plate width of 13.5M maximum.
Most offices are that width and unless you have a brief to build the building that size your width seems too big.

Using an L-Shaped form creates an "elbow" which gets little light.
An 11M-sided "elbow" is a lot of space to fill witha reception with no views, loos, a lift and a stairwell.
Also if you have your stair in the "elbow" your single direction travel dstance of 12M is exceeded by nearly 100%.
You'll need three stairs instead of two.

So first, before you go anywhere near costing the structure, talk to a commercial letting agent about your floor plate layout and depth.
Then appoint a design team and see what they can bring to the table in terms of adding light and amenity to wide floors.
If they can do something, you may end up with a lettable building of that width.
The increased light levels will offset the depth and have a positive effect on the eventual sale or let.

Otherwise the extra width and the reduced light and amenity may mean the build could suffer by comparison - in a recession - and won't let or sell well.
You could consider reducing the size and cost of the building and so increase its amenity without compromising its lettability and overall return.

De.Lite.Touch

Sorry its going to be apartments (more like flats to be honest) I put in in the initial post but should of put it in the title!

RKQ

OP it seems you have a full set of design drawings and I assume you have planning permission.

If this is the case then your design / planning permission drawings may show a column grid, giving proposed spans of floors etc. They might also give some idea of the intended structure subject to Enguneers design & specification.

I think you should discuss your drawings with a Structural Engineer and a Q.S. You will need a Design Team. They will be able to advise once they see your proposed building. You will need to apply for a Fire Cert, if you haven't already.

If you feel you are not willing to speak to a new Architect, why not approach an experienced Architectural Technician with full P.I insurance?

Good luck as its great to hear of a new 5 storey building which will begin construction soon.

cgarrad

Cheers ;-)

Anyway, the plans I have are floor plans, not structural so this is why im asking.

Once the 5 stories are up I can finish the fit out with what I know (built 2 houses before)

I can do any of the ideas I initially described, just wondering what would be the best (cheapest as well ;-))

It not I don't want an architect, I will be getting one, I was hoping for some real world experience!

dan_d

By "precasting the whole structure with formwork", I think what you mean is pouring it in-situ, ie shutters will be formed on site and concrete poured into them to create columns etc. That's quite common - bear in mind you will have to have rebar schedules for that, as steel reinforcement will be needed in the concrete.

I get a bit worried when you say you only have floor plans, not structural, and you're comparing building costs. You should have a structural engineer involved to design the structure of the building - columns/slabs/spec steel etc.

Your engineer will come up with the structure layout and based on that, you can price it. You can't really chose a construction type from thin air based on floor plans and say it's the cheapest or not, as you don't know what problems might arise and what exactly the structure requires for it to function - or just plain stand up.

I think the bottom line is that although you've built a couple of houses, it's just not the same thing, and you really really need to employ a design team. It's good to hear someone out there still building though!!

cgarrad

I am getting all the relevant professionals, I was just looking for a comparison between the options available, both on pros and cons and cost.

No worries, Ill ring an architect in the next day or two.

De.Lite.Touch

cgarrad wrote: »

(snip)
Sorry its going to be apartments (more like flats to be honest) I put in in the initial post but should of put it in the title!

The depth of plan vs visual amenity issue is worse for apartments than offices.
You can't light 8M deep aprtment spaces naturally on intermediate or ground floors unless you include lightwells.
I don't think you should bother doing anything else until you've had the site investigated and the building designed by somoene who knows what they're at.
The site investigation [incl. groundwater, soild type and site access] together with the state of the adjoining buildings will help your engineer decide on the best structural method.
The strengths and limitations of the structural method -vs- the brief will help inform your architect's design and how best it should be used to support the brief.

Take the necessary steps to start off.
Investigate the site, then the design.
After that you can cost the building.

-- De.Lite.Touch

Mellor

cgarrad wrote: »

I am getting all the relevant professionals, I was just looking for a comparison between the options available, both on pros and cons and cost.

No worries, Ill ring an architect in the next day or two.

Well you need to ask them these questions, make up a BoQ, tender it and compare costs.
Seeing as your building knowledge is limited at best, i'd leave any decisions to the professionals, barring maybe cost, i imagine you will dicate the budget available.



Mod note to all boards.ie users:
Boards.ie is not the place for a multistory building dicussion. Esp regarding structure.
Similar threads will not be entertained. Aspects of larger buildings are fine such as window selection, bedroom size, apartment layout etc.

mjth2004

IMO (apologies OP if I'm jumping off track) building control in this country is non existant - this needs to change! It's an ideal time to put together building control units within LA's, the numbers of very good 'input whichever design profession' with real cojstruction site experience are now there looking for work! A sort of poacher become gamekeeper might actually improve building standards!

If the OP wants to build of planning drawings there is no system in place to prevent this! As an arch tech who mainly dealt pulling together construction drawings, once all design team members input had be finalised the final construction package didn't resemble the earlier planning package apart from facade details!

I think prior to any project starting on site, a set of construction drawings including structural calculations should be provided for building control approval. An addition to this would be M&E calculations as well with new Part L coming down the line, as house building is becoming more of a science!

My two cents - fail to prepare, prepare to fail!

Poor Uncle Tom

mjth, your post is totally off-topic. This is not a debate on the merits of Building Control or what should or shouldn't be acceptable regarding building and planning details.

Warning: Stay on topic.