wide gaps in wood flooring

Hi
Can anybody please help? We have just bought a house with a lovely large (pine) wideboard wooden floor - running lengthways across the living room and dining room, each board is about 6 inches wide and 12 feet or more long.
The problem is that there are very wide gaps between the boards - as much at 5mm (or even more) in a few places and we can feel a draught coming up from the cellar beneath.
We want to fill these in - and had one quote to sand them, make up a cellulose-based filler with the dust and then filler them in and polish. Apparently this would look great and it'd cost about 500quid (which is within our budget).
The problem is that we got a second quote and the guy told us that the problem with cellulose, especially with wideboards, is that if they boards contract the cellulose could itself crack and we'd be left with long cracks running inbetween the boards - and, eventually, the filler would fall between the cracks and we'd be back to square one. Our second guy said that we could use some other filling material (not cellulose) but that this would be more expensive, and wouldn't colour-match as well.
I found a website - http://www.broadleaftimber.com/floors/technicalinfo/ftechnicalinfo7.html - which says " ensure that the filler is suitable for the size of gap you are filling - cellulose based fillers should be used for gaps over 3mm. " - which makes me think we would be OK after all with the cellulose.
Can anybody help?
Thanks in advance.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I have no experience of cellulose. I first tried PVA plus sawdust but that went dark and shiny on drying and contracted anyway. The other option of filling the gaps with wood slivers was super labour-intensive and needed at least a bandsaw.
I hunted around for fillers suitable for an applicator gun and after much fruitless searching and finding the small print specifically excluding filling of floorboard gaps I came across acrylic frame sealant in natural ( wood ) colour. Dow Corning make it.
My floorboards had up to 1/4" gaps, and that was after I lifted a couple of really wonky ones and regapped them!
I wasn't sure about the sealant falling through after movement so I caulked the floorboard gaps with twisted hemp strings. This was tedious, and may be unnecessary, certainly with small gaps.
I then laid masking tape down either side of all the gaps, and with something like 4 or 5 tubes of frame sealant for a 10x12 room I filled the gaps and smoothed off the sealant surface with a wet finger.
The sealant is light to start with but slowly darkens with age and is now slightly darker than an antique pine shade. I did all this in January, and found that after a year a few gaps opened up, though the sealant never fell through or sagged. I added additional sealant to caulk these gaps and all seems to be OK now. Remember the floorboards may dry out and shrink over time with the carpet above them now gone.
I repeated this in my hallway a year later, caulking only the largest floorboard gaps, this time with foam insulation instead of hemp. After 18 months there are no problems.
I can't see the point of an exact colour match between boards and filler, the filler lines being visible isn't intrusive at all. I suspect you could rub fine sawdust into the sealant as you go along to get a close match if that's really important.
Andy.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andy wrote:

What people don't realise is that sawdust is not a colour match for the boards. Different texture equals different "colour"
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
if you have an accessible cellar ,why not insulate from below much cheaper and will give a added benefit of better heat retention and no change to the exposed floor.
Alex
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Seconded. Maybe thin pine faced plywood pushed up against the boards between the rafters for appearance and to stopt the draft then celotex for insulation.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
There's this stuff which looks a good idea - http://www.stopg-p.co.uk / Anybody used it?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's not clear from the website excatly what this stuff loks like .A picture would have made this clearer .Also read this re T+G boards .
Stuart --------------------------------------------------------------------------------- STOPG-P is designed to exclude draught through gaps between 18 mm wide, especially gaps between square-edged wooden floorboards. The gap must be 10mm or more deep so that the seal can be pushed out of sight. This makes it unsuitable for tongue and groove boards. Exceptionally, the seal can be trimmmed with scissors to fit shallower gaps. -----------------------------------------------------------------------------------
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Stuart wrote:

---------------------------------------------------------------------------------
-----------------------------------------------------------------------------------
It seems to be a folded strip of polythene or something so that it springs open to close the gap if you poke it in pointed end down.
cheers Jacob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for your help everybody.
I think we've now decided not to try to colour match - but to go with a black acrylic gap-filler - after which we'll polish the boards again.
Before we go ahead do just let me know, anybody, if you think this is a bad idea.
normanwisdom wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
rebelmc wrote:

A black surround to a suspended wooden ceiling just looks like an empty space, and I guess the effect on floors would be the same i.e. the gaps will still look like gaps. Strangely enough, clear sealants don't look as good.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
rebelmc wrote:

We went this route using a product called Styccobond B94 , (2-3 litres ~ 15-25 worth does a standard room!) - it worked very well - filled upto 10mm gaps not probs and has stayed in place for over 3 years - including the hire of the sanding machine, sand paper and the filler we had change out of 100 and it took less than a day!! -
Any help Jon
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.