Mortar over PAP

GaryDidier

I would like some opinions from the experts here. I am renovating an old colonial. Planning radiant in the kitchen and office. This will be my first radiant application. The existing subfloors are 1 inch thick rough sawn boards. I would like to use approx 1- 1 1/4 inch mud base of mortar to encase the pex and level the floors. The kitchen will be finished with tile and the office will be laminate flooring. Will this work.

Thanx, Gary from Granville

hr

Yes, if

the floor joist can handle the extra load and weight of the overpour. Jump up and down in the middle of the span to see how stout the joist are! Can you still get below to beef them up if needed?

If the joist are undersized and deflect a tile job will forever crack!

Basic motar would not be a good underlayment. It's not meant to be poured that thick and may crack up

Gypcrete, a regular pea gravel concrete mix, or a Youkers mix. You want 3 times the aggreate size over the top of the tube. Pea gravel is considered a 3/8" size. If you use redi mix have them double the fiber to 3 pounds per yard for additional strength in thin pours.

I'd also add a shrink reduction agent to any thin pour concrete, especially with pea gravel mix. WR Grace is one brand, your batch plant should be able to guide you here. (The Yourker mix recipe has all the chemicals listed)

Or some of the new pourable polymers designed for leveling and able to be poured to a feather thin edge. $$$ey however!

A dry pack mud base (coarse sand and portland) makes an excellent base for direct tile application with thinset.

Regular pea gravel/ fiber concrete is fine for the areas to be wood floored.

When concrete or cement based products are poured over wood you need a slip sheet, like 6 mil plastic to prevent the cement from adhering to the wood. It also keeps the wood from absorbing all the waters of convience.

With gyp you actually put a latex primer over the wood to help adhere the gyp to the subfloor. It needs to be fairly clean also.

hot rod

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GaryDidier

Mud pack

Thanks, Hot Rod for your advice. The mud application I was referring to is what the old time tile setters used. Tar paper ( I will use 6 mil plastic), Chicken wire and a fairly dry mortar base. The floor is well supported. I was just wondering if one inch was enough of a base for the mud pack.

Thanx, Gary from Granville

hr

My concern would be the thickness over the tube?

Think I would use a 3/8" tube and make sure it was stapled every foot to keep it from springing up into you base mix.

Of course I would go with a PAP as it lies better.

You may want to shoot the floor and find the highest point and determine the coverage, over the tube, at that point. If you need to level the whole floor.

Not sure there is one correct term for that base. I have always called it dry pack or tile mud set. Has many different names for the same mix from area to area.

Have fun playing in the mud!

We are prepping a concrete slab with InsulTarp on top for a tile set like you describe. Uneven concrete exisiting floor will need a 3" thickness in some spots!

The homeowner is a union bricklayer, seems to have a handle on the install method and mud mix. He is going to have a local redi mix company deliver the dry pack in a mixer. That will be a first for me! Wonder how it will flow down the chute. Sounds like a lot of hand work. I may be sick that day and stay home. He is doing 1800 sq. feet! I should have pics next week.

Scott and I have it 2/3 tarped, meshed, and tubed.

hot rod

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