Extension floor - boarded or solid?

[fiveminutejob]

We are looking to have a small groundfloor-only extension built at rear of our semi to enlarge kitchen and dining area - which will then be open plan. The existing kitchen is solid floor; the dining bit is suspended T&G floorboards.

We simply visualised the kitchen would be extended out as a solid floor and the dining bit would be extended with new suspended floorboards to match the existing stuff.

Three possible builders have each said they would do the new bits entirely as solid floor - and looked blank when I pointed out that would give us a dining area with a part solid/part suspended floor, so not really acceptable. Plus it would also need to have a new ch radiator installed (above solid floor).

Is there something I am missing here? Maybe it's me. Or are they all just looking to do job in fastest/easiest way to get paid asap?

Advice and comments appreciated. Thanks.

 

[^woody^]

No thats how it is commonly done.

If you want part solid and part timber, then just specify it - but it will cost you much more.

And you may want to change you perception of builders, as it seems to be showing a certain lack of trust even before work begins

 

[Shytalkz]

Woody:

You could have the structural slab set slightly say 50 below existing finished floor, fix some battens on the top and then fit floorboards to that. Will give it the right amount of spring, be continuous with the existing and you'll be hard pushed to tell the difference (I'm assuming that it's a suspended timber floor at present?). There'll be a slight cost implication, but nothing too major, unless you've got kiln-dried oak or similar in mind.

 

[fiveminutejob]

Thanks Woody & Shytalkz. I do appreciate your time and input.

Woody: If there is any lack of trust just now it stems from the lack of willingness of the prospective builders in this case to even acknowledge that the customer's wishes are relevant. If it were technically impossible, I would happily accept that, learn from their explanation and move ahead. But clearly it is do-able, as Shytalkz suggests, and is no big deal to extend floorboards to floorboards. "Yes you can have that, but it will cost more" is not hard to say. But in each case we felt we were being talked into having part-solid/part-wood floor for no apparent technical reason.

Shytalkz: Thanks, that is helpful. Yes it is a typical suspended floor. When you say lower by "50" can you clarify depth and batten size you have in mind, please? If battens sit directly on a new concrete raft:

- would it give a noticeably different 'spring' to the existing joists? About 6-7 inch I think.

- what about under board ventilation? The only available through ventilation via existing front/rear airbricks would have been cut off at the back of the house by a new solid floor. How would a builder maintain ventilation?

All help and comments gratefully accepted so we can get it right for us and the builder, before work starts. Thanks.

 

[^woody^]

The only reason to make the floor timber or psuedo-timber is if you willl be having exposed boards.

If not there is no point at all in doing it in timber

 

[davebelushi]

Make sure that your builder is carefull not to restrict the ventillation to the suspended timber floor. I have seen this happen many times and the resultant sub floor condensation can cause all sorts of problems with fungal decay.

 

[Shytalkz]

Christ, I daren't use quotes after Woody's comments last night .

5MJ, in making my comments, I was assuming that you have floorboards as opposed to chipboard; and if the latter, would agree with the Woodster, really, although you could equally do the following for chipboard as well as boarding.

On the assumption that my initial assumption was correct, if you get my drift , you could have a structural oversite slab, the top of which stopped 48mm below top of the existing finished floor (with dpm underneath); plug and screw 25x50sw battens at the same centres as the existing joists (or percussion-fix) to the slab and fix 22 thick boards to match existing to this, which will give it some "bounce" like the original. If your existing boards are thinner/thicker, then adjust dimension from slab to top of boards to suit 25 battens + actual board thickness.

I think that's a fair comment to make regarding some builders trying to railroad you into what they want to do, as opposed to what you think you want. That said, there are also plenty of occasions where the client, through being a layperson, is not suggesting the most appropriate course of action.

However, you are the client and it's up to them to provide you with what you want, rightly or wrongly. Unless it's an obvious danger, which isn't the case in this instance.

 

[Shytalkz]

And DaveB's comments re venting are entirely relevant. You might need to consider piping some ventilation to the existing suspended floor construction under the new slab, it all depends on the layout that exists.

 

[fiveminutejob]

I did try on two occasions to leave thanks for the helpful comments - but on both occasions the posting facility was down (honest!).

So , better late than never....thanks for your time and trouble which is much appreciated.

 

[Vee239]

We're in the process of having an extension built at the rear of our house.
The Building Control surveyor has asked for brick piers to be built on the concrete to support joists.

 

[staningrimsby]

Hi 5MJ,

I to am having exactly the same extension as you with the same options i.e. T&G dining room and a concrete kitchen.

However i will be concreting the new extension floor and as far as ventilation to the dining room is concerned the BCO advised a 4" soil pipe in with the hardcore before blinding and DPM, then leading to a telescopic pipe with an air brick on the end, all available at screwfix.

The BCO said that this would be more than adaquate and comply with any relevant regulations.

Hope that helps,
Stan.