Special Construction Situations


OAK FLOORING OVER A RADIANT HEATED CONCRETE SLAB

Flooring is an insulator and may require higher water temperatures for a radiant heat system. Also an outside thermostat is recommended to anticipate rapid temperature changes. Boiler water temperature must be controlled to keep it to a maximum of 125°. This will limit the temperature of the slab surface to about 85°, an acceptable level for most mastics.


The flooring is installed as in any other slab project, except do not fasten plywood to concrete with either nails or powder-actuated fasteners. Turn on the heating system 4-5 days prior to delivery of the flooring to the job. The heat will drive extra or excessive moisture out of the slab.

 

(NOTE: Check flooring and mastic manufacturers' specifications for suitability of use over radiant heat.)

 

STRIP OAK FLOORING IN A WOOD PLENUM SYSTEMS

This method of construction utilizes a crawl space that is completely sealed from the outside as a plenum to which air from the heating/cooling system is supplied. The air then enters each room through floor registers.

 

A ground cover of polyethylene film is essential, as well as having the heating system operating for at least 4-5 days prior to delivery of the flooring to stabilize the moisture condition. No other special consideration is necessary in installation of the flooring. Proceed with previous recommended procedures and time tables.


Flooring Expanses 20 feet and wider. In large rooms, across diagonals and/or where flooring runs through doorways to produce an expanse over 20' wide, additional installation techniques should be considered. Begin line-out near the center of the space (i.e. across the center of the room with diagonal installation or near center line of total expanse), insert and glue a slip tongue in the starter strip groove, and proceed with installation in the two opposite directions. Inclusion of field expansion spaces may also be necessary in the wide expanse.


STRIP OAK FLOORING ON WALLS AND CEILINGS?

Because of its beauty and decorative quality, strip oak flooring is being used more and more for interior wall and ceiling applications.
Storage and handling practices are identical to those for a flooring installation, and precautions concerning moisture conditions must be observed. In particular, the building should be closed in with all doors and windows in place and all concrete, masonry and plaster thoroughly dry. On exterior walls install a vapor retarder within the wall system. Check with an HVAC engineer for proper placement.


The flooring can be nailed direct to the studs for a horizontal application.


For vertical or diagonal application to a stud wall, nail 1 1/2" thick furring strips (2 x 4s) to the studs at 12" spacing and nail the flooring to these strips.
For masonry walls, fasten lengths of 2 x 4s on 12" centers to the walls with concrete fasteners designed for the expected load. Nail size and schedule are the same as for flooring applications.


INSTALLATION OF GYMNASIUM FLOORS OVER A CONCRETE SLAB

Gymnasium floor products offered by NOFMA mills are most often made of 3/4" oak, pecan or maple. Some NOFMA mills make 25/32" maple. Beech and birch are also suitable. It is most important to have some resiliency built into these floors, but in most respects installation closely follows the screeds-in-mastic method recommended for conventional use, with a plywood or board subfloor installed over the screeds. Also, 2 layers of 1/2" plywood cushioned and laid on a 45° angle to each other may be used as a subfloor.


Acclimate all floor system materials to the established environment well in advance of installation.


Make sure the slab is dry and level with a good float finish. Maximum surface variation is 1/4" in 10'. Grind down high areas and fill low areas with concrete leveling compound.


Sweep the slab clean and prime with asphalt primer.* Let dry thoroughly and coat with asphalt mastic, using a notched trowel designed to apply at a rate of 50 sq. ft. per gallon. Embed a layer of 15 lb. asphalt felt or building paper, starting at a wall with a half sheet. Lap seams. Cover this with another layer of mastic and embed a second layer of asphalt felt or building paper, starting at the same wall with a full sheet to cover the seams of the first layer.


Either hot or cold mastic is satisfactory. If the cold type is used be sure to allow time (2 hours) for solvents to evaporate before applying the building paper.
An alternate method for a surface vapor retarder is to embed a 4 to 6 mil polyethylene film in a cold mastic Lap film edges 6".


A suspended concrete slab with a controlled environment below needs no surface vapor retarder.


A suspended slab over exposed earth or an uncontrolled environment requires a proper vapor retarder over the slab. In this case cross ventilation below the slab is essential, and, if over exposed earth, a ground covering of 6 mil polyethylene should be provided.


Screeds used and their application are identical to that previously described, with these exceptions. Place them on 12" centers, (9" centers with 3rd grade flooring) unless a subfloor is to be used, then 16" centers are allowed. Leave 2" space between the ends of the screeds and the base plate on all walls to allow for expansion.
The strip flooring may be nailed directly to properly spaced screeds, but a much more sound and satisfactory floor can be achieved by installing a subfloor of 3/4" minimum plywood or 3/4" dressed square-edged boards no wider than 6". Follow arrangement and nailing schedules described previously. If boards are used, leave 1/2" space between them.

 


Start laying the finish flooring in the middle of the room and work toward the walls. Engage the first two courses groove-to-groove with a slip tongue glued into one groove. Join the strips and face nail as well as blind nail both courses. Proceed with succeeding courses in the conventional manner, using either 7d or 8d flooring nails, 2" flooring cleats or 2" 15 gauge staples with 1/2" crown.


After an area 3' or 4' wide has been laid across the room, leave a 1/16" expansion space between the last course laid and the next course. Repeat this expansion space evenly at 3' to 4' intervals across the room. Different area environmental conditions may require more or less field expansion.


Nailing is most important. Nail to all screeds and to both screeds when a strip passes over a lapped screed joint. All end joints do not need to meet over screeds but adjacent strips should not break over the same screed space.


If a subfloor is used, nails must be no more than 10" to 12" apart with a minimum of 2 nails per board near the ends (1"-3") along the length of strips.
Allow 2" expansion space along all walls and at doorways. This can be covered at the walls with an angle iron bolted to the wall or a special wood molding, and at doorways by a metal plate designed for such use.


After installation and through the sanding and finishing process, the interior environment should be maintained near to an occupied condition. Extended times with no HVAC in operation should be avoided. This can promote a static "green house" effect. These conditions can allow an abnormal increase in moisture which may adversely affect flooring.