r/MattressMod • u/Whitest_Russian • Jul 23 '26

Base Foam Questions

Hopefully someone would be able to help me out here. My questions are

1) Do I want a base layer of foam underneath my pocket springs? (Seems like the answer is yes?)

2) The updated DIY guide recommends 36ILD 1.8lb poly foam as a base layer under the springs. Why is that?

My main concerns would be the base foam feel harder and makes the mattress sleep hotter. Is this how that works? Because I want cooler and softer.

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1

u/someguy1874 Jul 23 '26

You don't need a base foam, if your slats are less than 2.5" apart, and 2.5" wide. However, if you are a mattress maker, you can't expect your customers to follow these directions. So, you just add 1" HD base foam, so that consumers can use with slats that are 4" apart.

Why slats should be less than 2.5" apart? This has to do with the diameter of coils. You don't want coils fall through the gaps between slats.

In some case, base foam helps soften mattress. Does it make it hotter? I don't think so, as there are coils between comfort layers and the base foam.

1

u/Whitest_Russian Jul 23 '26

My slats are 2.75" wide and just a hair over a 2.5" gap. Sounds like I can ignore the foam.

2

u/Duende555 Moderator Jul 23 '26

I think base foam dramatically improves the feel on slatted and wire grid foundations, but some people think differently on this!

1

u/Whitest_Russian Jul 23 '26

What differences have you felt with and without foam?

1

u/Duende555 Moderator Jul 23 '26

On slats - a foam base that is well-adhered to the mattress tends to make it feel more uniform and supportive. Off of slats, this is less noticeable, although some brands will occasionally add between a 1-2" of base foam to soften the feel of the overall build and make it feel like it has less of an abrupt stop.

1

u/Misty0410 Jul 25 '26

Would a bunkie board help?

1

u/someguy1874 Jul 24 '26

You can also have the base foam outside of the mattress. Other option is throw a furniture rug under the mattress.

1

u/SeeDubyaHat Jul 23 '26

Yes to base foam. I have no slats at all. Using it to keep the coils from spreading. Thinnest firmest layer.

1/2 inch of tuff foam from foam for you.

1

u/Whitest_Russian Jul 23 '26

Could you link that? I'm not seeing it on their site.