Block and Beam vs Suspended floor Cost

[Ben Kerr]

Hi

Not sure if this is the place to ask. I am trying work out the difference in price between a suspended floor and block and beam. It's for an area just over 30m square. The reason being: we are having an extension built and the builders persuaded us to go with a suspended floor rather than block and beam, for reasons of speed. Unfortunately it doesn't seemed to have saved any time; and while we were discussing the change in plan, it was confirmed that it would be cheaper. We have discovered that we need a more expensive option for our windows and are hoping we can used the money saved to pay for this. The builder has been slow and vague in getting back so I am trying to find out myself.

Also into the mix the builder said that the original block and beam would have been too long for standard block and beam and half size blocks would have been needed.

Thanks for any advice in advance.

 

[rssteve]

What's the span

 

[Ben Kerr]

What's the span

Thanks for the reply,
the extension goes out 6m from the house, the width 3m out is about 6m, then it narrows to about 5.5m.
does that make sense?

 

[rssteve]

Starts at 3m wide then narrows to 5.5m. Don't understand.

 

[rssteve]

I guess wood would have been cheaper if you had a floating floor on top of the insulation. Would save having to screed the block and beam.

 

[tomfe]

Block and beams is a suspended floor.
Were the options timber and block and beam?
Timber is a fair bit cheaper and easier to install but you normally have the roof on before you do this so you can't work off the floor to build the walls.
Block and beam is good for large extensions/ new builds as it's quick to lay. It's also not normally cost effective for small floor areas.

Why didn't you do a ground bearing floor slab are you on a slope?

 

[^woody^]

When you have to live with it for years, it's worth thinking about whether "speed of construction" is for the customers benefit or the builder's.

It's not 1950 anymore, and a timber floor would only be chosen for specific reasons. And similarly for a concrete suspended floor.

One of the reasons not to select either is that they bounce all over the place.

 

[Ben Kerr]

Starts at 3m wide then narrows to 5.5m. Don't understand.

Sorry I will tried to be more clear:
The extension goes out from the house 6 meters, it is almost 6 meters square. However it narrows 3 meters from the house from 6 meters to 5.5m. Meaning that at the house it is 6 meters wide and furthest from the house it is 5.5m with the change happening half way in one step in.
Is that any clearer?

 

[Ben Kerr]

Block and beams is a suspended floor.
Were the options timber and block and beam?
Timber is a fair bit cheaper and easier to install but you normally have the roof on before you do this so you can't work off the floor to build the walls.
Block and beam is good for large extensions/ new builds as it's quick to lay. It's also not normally cost effective for small floor areas.

Why didn't you do a ground bearing floor slab are you on a slope?

Hi yes, sorry the choices were timber or block and beam. We didn't go for a slab because it is on a slope and we are leaving a space below for storage. It's roughly 6m square have you any idea of what difference in price might have been?

 

[Ben Kerr]

When you have to live with it for years, it's worth thinking about whether "speed of construction" is for the customers benefit or the builder's.

It's not 1950 anymore, and a timber floor would only be chosen for specific reasons. And similarly for a concrete suspended floor.

One of the reasons not to select either is that they bounce all over the place.

Unfortunately speed of construction is now an issue. They started in November saying the outer shell would be finished around the end of December/start January. We are now at the end of March and still are a long way of just getting the shell up, however this seems to be par for the course in the UK.

 

[^woody^]

If they are late then it's a contract issue for damages, and not compromises.

Anyhow, I cant understand why it's last minute, when such a fundamental thing should have been planned months ago.

If you choose timber, then not only is it inferior to concrete and more risk long term, but you will need it fire protecting if you are to use the sub floor for storage, and you might need an interlinked alarm extending to the storage area too.

So it's not just a choice for you or the builder, you need the designer's input too.

 

[tomfe]

How much of a slope have you got?
Where are you up to on the build?
You need a concrete oversite with at least a 150mm void for timber suspended floor so you need to have made this decision fairly soon if you need to alter ground levels etc. The T beams are built into the internal skin of the wall so if you are past floor level - insulation and screed height then that's going to add cost to either build up a sleeper wall off the foundations or try and cut holes and get the beams in.

We have had some good weather since November so they should have been able to crack on fairly well.

I would always try and use a ground slab is possible.

 

[Ben Kerr]

If they are late then it's a contract issue for damages, and not compromises.

Anyhow, I cant understand why it's last minute, when such a fundamental thing should have been planned months ago.

If you choose timber, then not only is it inferior to concrete and more risk long term, but you will need it fire protecting if you are to use the sub floor for storage, and you might need an interlinked alarm extending to the storage area too.

So it's not just a choice for you or the builder, you need the designer's input too.

Time to completion wasn't in the original quote, so we don't have a leg to stand on unfortunately.

 

[Ben Kerr]

How much of a slope have you got?
Where are you up to on the build?
You need a concrete oversite with at least a 150mm void for timber suspended floor so you need to have made this decision fairly soon if you need to alter ground levels etc. The T beams are built into the internal skin of the wall so if you are past floor level - insulation and screed height then that's going to add cost to either build up a sleeper wall off the foundations or try and cut holes and get the beams in.

We have had some good weather since November so they should have been able to crack on fairly well.

I would always try and use a ground slab is possible.

We already agreed to the change and they have put the timber alternative in already. So we are already committed, I'm just trying to work out if we can get something out of the change, by using the price difference to improve the windows that are going in, as haven't had the time saving.

As to the good weather since November: we have had a variety of justifications for delays including: waiting for blocks (they ran out quite a few times), weather, man flu, waiting for drawings from an engineer. We have to take them at there word but as I said above this seems to be the way things are in the UK.