Hi,

I will be laying a solid oak floor which 22mm x 180 wide. I will be nailing one edge through the tongue in the normal way and leaving an expansion gap around the edge of the room.

I cant get it straight in my head why an expansion gap between each board is not required, I would have thought the since I am nailing on one edge there should be some space left between the boards to allow a little bit of expansion e.g. a millimeter of 2. I havent seen this mentioned anywhere ? Can someone clarify this point please.

John

The floor system will expand and contract as a unit, in general.
The angled nailing pattern allows for this.
In large installations such as gymnasiums, we insert an expansion gap of 1/8th inch every 4 feet of run.
If you had to do this in a residential application, the carpet people would love you. Susie homemaker would not tolerate gaps like that in her floor either between individual boards or every 4 ft.
It is better to be pro-active with your floor by having proper facilities to monitor and maintain a near constant relative humidity of 45%.
An impossible task, but hardwood will remain stable between 35-50 percent which is easily attained with the use of humidifiers, properly installed and functional; for the heating season, and if needed, a de-humidifier for the hot moist summer months.

That is not true for all wood flooring, only floating floors, where each board is bonded to the next, but not when each board is individually fastened to the substrate.



Gaps are left between each row, when conditions call for it, like acclimating wood to a very dry home in the winter, and you know it is going to be a lot more humid as spring and summer roll in. Not every 4 feet across the room, or like said, Mrs. homeowner will have a cardiac. Educating the home owners about the hygroscopic nature of all wood, before the sale, make thing go a lot better when they happen.

So what you are saying is, the 3/4 inch expansion tolerance at the walls is only for the last board?

In the event of a major flood, the rapid expansion doesn't push walls OFF the foundation.

Never seen a ¾ expansion gap that was there be taken up and compress the wall. It will buckle out in the field way before that happens.

The first time I heard that (from Steve Seabaugh) I was as amused as I am now.
I once installed a Sheoga 3+4+5 plank in a cottage in Muskoka, one side of the room (36 ft. by 21 ft.) was a glass wall, the other was drywall over 2X6 studs. Architect insisted I lay the floor tight to the glass wall, leaving one inch at drywall side and signed off on it contrary to my recommendations. One month later, this was in August, I returned to find the floor had grown tight against the drywall and had bowed upwards 3 feet (really!) in the centre of the room.
When i removed some of the central area, I was able to measure, and determine that the floor as a whole had growm just over 6 inches in total.
No damage to either the stud wall or the glass wall. The angled nails in most of the body of the floor allowed the floor to lift off the subfloor.

Austin, while in gereral, I am in agreement with most of your suggestions and thoughts, in this one, I must disagree. The very nature of flooring and fasteners combined, would never allow sufficient lateral force to push a house off its foundation.

The reason for the growth of the floor was a total lack of humidity controls, Cottage was closed up tight as a drum, while the owners were on a tour. The combination of new construction, location of cottage, and no de-humidifiers or A.C. caused damage to almost every wood component in the structure, including a piano that was so warped that it had to be trashed.

okay after a bit of research i have come up with the following for my solid oak floor (22millimeter thick)

1) let the wood acclimatise for a couple of months in the house before laying
2) lay ideally in the time of year when the humidity is towards the highest
3) buy a moisture meter and gauge whether the wood is wet of dry (or just right) before commencing laying, if it is too dry then there could be trouble
4) leave a 3/4 inch expansion gap at the edge of the room
5) lay the wood and nail the tounge, leaving no gap between the boards
6) cross your fingers and hope for the best

how does this look ?

Thats pretty standard procedure. Although it may not take two months to acclimate the floor, it is good that you have sufficient time, just in case.

Howard Brickman, told us about installing in historic homes around the Boston area.
You cannot take off the Base boards!! and they don't do 1/4 round. You do a replacement because it can no longer be sanded and reinstall tight to the base, no gap. Now, it takes someone with a lot of knowledge or big A$$ nads to do that, eh? Howard does it all the time, without issue and he has a lot of knowledge and I'm clueless about the other.

He leaves expansion out in the field if needed. He knows how to calculate if it is needed.

Ya, we do some work under cicumstanses like that too. The Historical (hysterical?) Society here in T.O. are adamant about not disturbing surrounding architectural features when working on the floors. (and other things I imagine).
Hate to use an over-worked phrase, but that is where "thinking outside the box" comes in handy.
Expansion joints within the floor will alleviate the need for leaving a space around the perimeter. We fill these with a flexible colour matched caulking to help conceal them, but it does reduce their effectiveness to a degree, so more are needed.

One project we worked on, the building had settled so much that the floor not only ran upwards, but on a slant as well. No way to put a big machine on it so we went back to 19th century style and hand scraped 1400 sq. ft. of flooring, and finished off with hand belt sanders. Can you imagine, the crew actually wanted to be paid extra for this

It is common in my area, to find pre WW11 homes where the baseboards are installed prior to the floors and there is no baseshoe. Then we'll find the flooring has been installed tight to the baseboards. But there are a few reasons why this worked for the most part. First, the flooring was commonly quartersawn. Second, it was 5/16" facenailed. Third, these were not installed as tight as they often appear. So when a facenailed 5/16" gets real wet or exposed to high humidity levels, it just buckles right up. It pulls the nails right out of the subfloor and peaks up like a mountain range. There would be no chance it could move a wall as it would continue to buckle and lift. So even though little attention was paid to acclimation, humidity or moisture levels, for the most part, these floors worked.

We dont see that style of floor up here, but am familiar with it to a degree. This in another discussion here, someone has a water damage claim on that type of floor.
But ya, being quartersawn really helps reduce the expansion tolerance needed.

so, from what has been said so far it seems that I will need to make sure the moisture content is correct before I go ahead with the lay. If I bought a moisture meter what should I be aiming for before laying, I guess this will depend on how humid my place is likely to get .....

Where do you live?

I live in scotland.

The relative typically relative humidity varies between 90% to 75%.

I am wondering how this change is likely to vary the width of the boards, I guess the question is what is the relationship between a 15% change in RH to the moisture content of the wood. I have some information which I can use to determine the swelling or shrinkage based on the type of wood and change in moisture content.

I am still struggling to get my head round how I am going to avoid too much swell or shrinkage....